Geodynamic mechanism responsible for the generation of Silurian granitoids and the tectonic evolution of the Qilian orogenic belt remains controversial. In this study, we report the results of zircon U–Pb age, and sy...Geodynamic mechanism responsible for the generation of Silurian granitoids and the tectonic evolution of the Qilian orogenic belt remains controversial. In this study, we report the results of zircon U–Pb age, and systematic whole-rock geochemical data for the Haoquangou and Liujiaxia granitoids within the North Qilian orogenic belt and the Qilian Block, respectively, to constrain their petrogenesis, and the Silurian tectonic evolution of the Qilian orogenic belt. Zircon U–Pb ages indicate that the Haoquangou and Liujiaxia intrusions were emplaced at423 ± 3 Ma and 432 ± 4 Ma, respectively. The Haoquangou granodiorites are calc-alkaline, while the Liujiaxia granites belong to the high-K calc-alkaline series.Both are peraluminous in composition and have relatively depleted Nd isotopic [ε_(Nd)(t) =(-3.9 – + 0.6)] characteristics compared with regional basement rocks, implying their derivation from a juvenile lower crust. They show adakitic geochemical characteristics and were generated by partial melting of thickened lower continental crust. Postcollisional extensional regime related to lithospheric delamination was the most likely geodynamic mechanism for the generation of the Haoquangou granodiorite, while the Liujiaxia granites were generated in a compressive setting during continental collision between the Qaidam and Qilian blocks.展开更多
The Xiaobaishitou gabbro-diorite pluton comprises a medium-grained gabbro-diorite suite and a fine-grained diorite suite,which intrude the Kawabulag Group in the East Tianshan Orogen of the Central Asian Orogenic Belt...The Xiaobaishitou gabbro-diorite pluton comprises a medium-grained gabbro-diorite suite and a fine-grained diorite suite,which intrude the Kawabulag Group in the East Tianshan Orogen of the Central Asian Orogenic Belt(CAOB).A combination of mineral chemistry,zircon U-Pb age,whole-rock geochemistry,Sr-Nd isotopes,and in situ zircon Hf isotopes for newly found gabbro-diorite from the Xiaobaishitou district in the Central Tianshan Terrane(CTT)is presented to investigate the petrogenesis and tectonic or even crustal evolution of the East Tianshan Orogen.Laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS)zircon U-Pb analyses indicate that the gabbro-diorite was formed at 324.7±2.4 Ma.The isolated clinopyroxene formed under higher P-T-fO_(2)melt conditions(10.7–14.6 kbar;1199–1269℃;high fO_(2))than those for the hornblende,plagioclase,and zircon(557–687℃;moderate fO_(2))in the gabbro-diorite,which reveals a multilevel,magmatic storage system.The gabbro-diorite is characterized by fractioned REE patterns,enriched LILEs(e.g.,Ba and Pb),negative anomalies of HFSEs(e.g.,Nb and Ta),and low La/Yb and Sr/Y ratios,which are typically indicative of crustal contamination and accounted for by subduction-related fluids.The rock also characterized by typical features of high compatible elements(MgO=3.14–11.65 wt%,Cr=1–157 ppm,Ni=6–830 ppm),high Mg^(#)(47–74),positiveε_(Hf)(t)values(+5.1 to+10.3)andε_(Nd)(t)values(+2.3 to+4.4).These features suggest that the Xiaobaishitou gabbro-diorite was most likely derived from metasomatic mantle and contaminated minor crustal components.Taking into account the spatial and temporal distribution of the Carboniferous magmatic rocks in the CTT,we suggest the formation of the Xiaobaishitou gabbro-diorite was attributed to southward subduction of the Kangguer Ocean.展开更多
The Bangbule skarn lead-zinc(Pb-Zn)deposit(>1 Mt Zn+Pb)is located in the western Nyainqentanglha polymetallic metallogenetic belt,central Tibet.Lenticular orebodies are all hosted in skarn and developed in the cont...The Bangbule skarn lead-zinc(Pb-Zn)deposit(>1 Mt Zn+Pb)is located in the western Nyainqentanglha polymetallic metallogenetic belt,central Tibet.Lenticular orebodies are all hosted in skarn and developed in the contact zone between the quartz porphyry and carbonate strata of the mid Paleozoic Middle to Upper Chaguoluoma Formation as well as in carbonate and sandstone beds of the Upper Paleozoic Laga Formation.As a newly discovered skarn deposit,the geological background and metallogenesis of this deposit remain poorly understood.Detailed petrological,geochemical and geochronological data of the ore-related quartz porphyry,helps constrain the mineralization age and contributes to discussion on the ore genesis of the Bangbule deposit.Both endoskarn and exoskarn are identified in the Bangbule deposit.From quartz porphyry to carbonate formation,the exoskarn is zoned from proximal garnet skarn to distal pyroxene skarn.Zircon U-Pb dating results show that the quartz porphyry formed at 73.9±0.8 Ma.Geochemical analysis results show that the quartz porphyry has high contents of SiO_(2)(71.40–74.94 wt%)and K_(2)O+Na_(2)O(3.76–8.46 wt%)with A/CNK values of 0.69 to 1.06.Besides,the quartz porphyry is enriched in large ion lithophile elements(LILEs)and light rare earth elements(LREEs)and have lowεNd(t)(from-8.25 to-8.19)and high initial(^(87)Sr/^(86)Sr)i values(0.713611–0.714478).Major,trace elements and whole-rock F concentration analysis results from the endoskarn samples show higher TFe_(2)O_(3),MgO,CaO,Pb+Zn,W,Sn,Mo and F etc.,and lower alkalis(K_(2)O,Na_(2)O,Sr and Ba)than those of fresh quartz porphyry,indicating that the early ore-forming fluids were an Ca-Fe-F-enriched fluid.Massive ore in the proximal skarn might be related to the high F content in the magma,which lowered the solidus temperature of the quartz porphyry magma and caused a lower temperature of the ore-forming fluids,as well as facilitating the precipitation of sphalerite and galena.Based on the geochemical characteristics presented in this study,we propose that the ore-related quartz porphyry was formed by partial melting of crust materials with some juvenile crustal component input.The partial melting of the middle-upper crust after the initial enrichment of lead and zinc elements are important for the formation of Pb-Zn deposits.The case study of the Bangbule deposit has proven that there is still a crust-derived magmatic source region in the western segment of the central Lhasa terrane.Therefore,there is still great potential for Pb-Zn mineralization and Pb-Zn exploration.展开更多
The Rb-Sr whole-rock isochron,age 1636±66 Ma of Mirgarani granite,is the one of the oldest granite dated in the northwestern part of the Chhotanagpur Granite Gneiss Complex(CGGC).The initial Sr ratio is 0.715...The Rb-Sr whole-rock isochron,age 1636±66 Ma of Mirgarani granite,is the one of the oldest granite dated in the northwestern part of the Chhotanagpur Granite Gneiss Complex(CGGC).The initial Sr ratio is 0.715±0.012(MSWD=0.11),showing an S-type affinity.The Mirgarani granite has intruded the migmatite complex of the Dudhi Group and forms the Mirgarani formation comparable to the granites of the Bihar Mica Belt around Hazaribagh(1590±30 Ma).The present studies have established the chronostratigraphy of the Dudhi Group and adjoining areas in CGGC.Petro-graphic and geochemical studies revealed that the granite is enriched in Rb(271 ppm),Pb(77 ppm),Th(25 ppm),and U(33 ppm)and depleted in Sr(95 ppm),Nb(16 ppm),Ba(399 ppm)and Zr(143 ppm)contents as compared to the normal granite.The Mirgarani granite is a peraluminous(A/CNK=1.23),high potassic(K_(2)O 6.42%),Calc-Alkalic to Alkali-Calcic{(Na_(2)O+K_(2)O)-CaO=6.29}S-Type granite,a feature supported by the presence of modal garnet and normative corundum(2.68%).The Mirgarani granite is considered to have been formed by the anatexis of a crustal sedimentary protolith at a depth of approximately 30 km with temperatures ranging from 685-700℃ during the Co-lumbian-Nuna Supercontinent.展开更多
The Songnen–Zhangguangcai Range Massif(SZRM)is located in the eastern Central Asian Orogenic Belt and crops out over an extensive part of NE China.The massif was originally thought to contain numerous Precambrian ter...The Songnen–Zhangguangcai Range Massif(SZRM)is located in the eastern Central Asian Orogenic Belt and crops out over an extensive part of NE China.The massif was originally thought to contain numerous Precambrian terranes(e.g.,Xingdong,Dongfengshan,Yimianpo and Zhangguangcailing groups).However,more recent zircon U–Pb dating indicates that the majority of these so-called Precambrian sedimentary and igneous rocks actually formed during either the Paleozoic or Mesozoic and contain only minor Precambrian components(Wang et al.,2014).The presence of Neoproterozoic and Paleoproterozoic detrital zircons with magmatic origins from and Paleozoic units of the SZRM indicating that this area occurs Proterozoic magmatism(Wang et al.,2014),whereas no Proterozoic magmastism has been found.Recently,Pei et al.(2007)reported the ca.1800Ma magmastism,as evidenced by the data of exploration drillholes in the southern Songliao basin.However,an alternative view is that the basement within the SZRM is predominantly Phanerozoic,as evidenced by the presence of Paleozoic fossils and comparatively rare geochronological data(Guo and Liu,1985;Wu et al.,2011),meaning that the ca.1800 Ma rocks in this area may be a tectonically emplaced slice of the North China Craton(Zhang et al.,2005).All of this means that the age and nature of the SZRM basement,and whether this area records Neoproterozoic magmatism,remain unclear.This study presents new geochronological,whole-rock geochemical,and zircon Hf isotopic data for early Proterozoic granitoids within the eastern margin of the SZRM of NE China.These data provide insights into the Neoproterozoic tectonic setting of the SZRM and the links between this magmatism and the evolution of the Rodinia supercontinent.The zircon U–Pb dating indicates that the Neoproterozoic magmatism within the SZRM can be subdivided into two stages:(1)a^917–911 Ma suite of syenogranites and monzogranites,and(2)an^841 Ma suite of granodiorites.The 917–911 Ma granitoids contain high concentrations of Si O2(67.89–71.18 wt.%),K2O(4.24–6.91 wt.%),and Al2O3(14.89–16.14 wt.%),and low concentrations of TFe2O3(1.63–3.70 wt.%)and Mg O(0.53–0.88 wt.%).They are enriched in the light rare earth elements(LREE)and the light ion lithophile elements(LILE),are depleted in the heavy REE(HREE)and the heavy field strength elements(HFSE;e.g.,Nb,Ta,and Ti),and have slightly positive Eu anomalies,indicating they are geochemically similar to high-K adakitic rocks.They have zirconεHf(t)values and TDM2 ages from–4.4 to+1.5and from 1915 Ma to 1592 Ma,respectively,suggesting they were derived from a primary magma generated by the partial melting of ancient thickened lower crustal material.In comparison,the 841 Ma granodiorites contain relatively low concentrations of Al2O3(14.50–14.58 wt.%)and K2O(3.27–3.29 wt.%),relatively high concentrations of TFe2O3(3.78–3.81 wt.%)and the HREE,have negative Eu anomalies,and have zirconεHf(t)values and TDM2ages from–4.7 to+1.0 and from 1875 to 1559 Ma,respectively.These granodiorites formed from a primary magma generated by the partial melting of ancient crustal material.The^917–911 Ma magmatism within the SZRM is inferred to have formed in an orogenic setting,whereas the^841 Ma magmatism formed in an anorogenic setting related to either a post-orogenic tectonic event or the onset of Neoproterozoic continental rifting.It is proposed that the microcontinental massifs within the SZRM formed during or following the final stage of assembly of Rodinia before rifting away from the Tarim Craton in response to Rodinia breakup.展开更多
It is well known that there are widespread igneous events at^2100 Ma in the Eastern North China Craton;however,their tectonic environments are controversial.They were thought to be either related to an intra-continent...It is well known that there are widespread igneous events at^2100 Ma in the Eastern North China Craton;however,their tectonic environments are controversial.They were thought to be either related to an intra-continental rifting展开更多
Objective The Late Cretaceous Xiuwacu ore-bearing porphyry is located in the Geza area of southern Yidun arc,SW China.In this area,the rock mass is mainly composed of three lithofacies:biotite granite porphyry,monzonitic
We performed geochronological and geochemical analyses of the A-type granite in the Hongol area, central Inner Mongolia, to determine its age, petrogenesis and tectonic setting, which are significant for clarifying th...We performed geochronological and geochemical analyses of the A-type granite in the Hongol area, central Inner Mongolia, to determine its age, petrogenesis and tectonic setting, which are significant for clarifying the Late Paleozoic tectonic evolution of the Xing'an Mongolian Orogenic Belt(XMOB). The rock type of the A-type granite in the Hongol area is alkali-feldspar granite, and it constitutes a western part of the Baiyinwula-Dongujimqin A-type granite belt. Zircon U-Pb geochronology yields ^(206)Pb/^(238)U ages ranging from 293 to 286 Ma for the alkali-feldspar granite, indicating this granitic pluton formed in the Early Permian. The alkali-feldspar granite is high in silica(SiO_2=75.13 wt%-80.17 wt%), aluminum(Al_2 O_3=10.59 wt%-13.17 wt%) and alkali(Na_2 O+K_2 O=7.33 wt%-9.11 wt%), and low in MgO(0.08 wt%-0.39 wt%) and CaO(0.19 wt%-0.70 wt%). It is obviously enriched in LILEs such as Rb, Th and K,depleted in HFSEs such as Nb, Ti, La and Ce, with pronounced negative anomalies of Nb, Ti, P, Eu, Sr and Ba. Its Sr-Nd-Pb isotopic compositions show positive ε_(Nd)(t)(+0.72-+3.08), low T_(DM2)(805-997 Ma),and high radioactive Pb with(^(206)Pb/^(204)Pb)_i of 18.710-19.304,(^(207)Pb/^(204)Pb)_i of 15.557-15.604 and(^(208)Pb/^(204)Pb)_i of 37.887-38.330. Petrological characteristics and geochemical data suggest that the alkalifeldspar granite in the Hongol area belongs to aluminous A-type granite. This A-type granite formed in a post-collisional extensional setting and was generated by the partial melting of felsic rocks in the middlelower crust resulting from post-collisional slab breakoff. It is suggested that the Paleo-Asian Ocean was closed before the Permian in central Inner Mongolia.展开更多
The Cenozoic geological hallmark of Western Yunnan is the characteristic voluminous Late Cretaceous-Eocene granites;however, their geological background and petrogenesis have not been well constrained and elucidated. ...The Cenozoic geological hallmark of Western Yunnan is the characteristic voluminous Late Cretaceous-Eocene granites;however, their geological background and petrogenesis have not been well constrained and elucidated. In this study, we present new zircon U-Pb dating, along with geochemical and Sr-Nd-Hf isotopic data for granites from the Tengchong–Lianghe granitoid belt(as abbreviated to Tengliang belt) and West Yingjiang batholiths from the Tengchong block. The mineralogical and geochemical features of the Tengliang granites and the West Yingjiang batholiths are ascribed to aluminous S-type granites and weak peraluminous I-type, respectively. Zircon U-Pb analyses yielded consistent ages ranging from 67.5 Ma, 68.4 Ma and 66.2 Ma from the Tengliang granitoid belt and 50.4 Ma to 60.8 Ma for three samples from the west Yingjiang batholiths. The Tengliang granites were emplaced during the Late Cretaceous(68-66 Ma) and demonstrate negative ε_(Hf)(t) values(-24 to-4) and initial ~(87)Sr/~(86)Sr ratios of 0.7101–0.7139 and significant negative ε_(Nd)(t) values from-8.91 to-13.2, indicating a Proterozoic sedimentary source or enriched components. The hornblende-bearing I-type granites from West Yingjiang are characterized by lower initial ~(87)Sr/~(86)Sr ratios of 0.7076–0.7106, compared to Tengliang granite and negative whole-rock ε_(Nd)(t) values from-4.0 to-11.9. The early Eocene west Yingjiang gneissic granites show wide ranges of ε_(Hf)(t) values from +7.4 to-8.5 and T_(2DM) of 1.30–0.65 Ga, indicating partial melting of ancient crust with contributions of depleted mantle materials. In combination with the regional background and previous studies, we propose that such a spatio-temporal distribution of the Tengchong granitoid belt might be related to the rollback or angleswitching of the Neo-Tethyan subducting slab. This study sheds new light on the evolutionary history of the Tengchong block.展开更多
Carboniferous magmatism is one of the most important tectonothermal events in the Central Asian Orogenic Belt(CAOB). However, the final closure time of the Kalamaili Ocean between East Junggar and Harlik Mountain is s...Carboniferous magmatism is one of the most important tectonothermal events in the Central Asian Orogenic Belt(CAOB). However, the final closure time of the Kalamaili Ocean between East Junggar and Harlik Mountain is still debated. Early Carboniferous(332 Ma) and late Carboniferous(307-298 Ma) granitic magmatism from Kalamaili fault zone have been recognized by LA-ICP-MS zircon U-Pb dating. They are both metaluminous highly fractionated I-type and belong to the high-K calc-alkaline. The granitoids for early Carboniferous have zircon εHf(t) values of-5.1 to +8.5 with Hf model ages(TDM2) of 1.78-0.83 Ga, suggesting a mixed magma source of juvenile material with old continental crust. Furthermore, those for late Carboniferous have much younger heterogeneous zircon εHf(t) values(+5.1 to +13.6) with Hf model ages(TDM2=1.03-0.45 Ga) that are also indicative of juvenile components with a small involvement of old continental crust. Based on whole-rock geochemical and zircon isotopic features, these high-K granitoids were derived from melting of heterogeneous crustal sources or through mixing of old continental crust with juvenile components and minor AFC(assimilation and fractional crystallization). The juvenile components probably originated from underplated basaltic magmas in response to asthenospheric upwelling. These Carboniferous highly fractionated granites in the Kalamaili fault zone were probably emplaced in a post-collisional extensional setting and suggested vertical continental crustal growth in the southern CAOB, which is the same or like most granitoids in CAOB. This study provides new evidence for determining the post-accretionary evolution of the southern CAOB. In combination with data from other granitoids in these two terranes, the Early Carboniferous Heiguniangshan pluton represents the initial record of post-collisional environment, suggesting that the final collision between the East Junggar and Harlik Mountain might have occurred before 332 Ma.展开更多
The Changning-Menglian Belt represents the main Paleo-Tethyan Suture in the southeastern Tibetan Plateau,which divides Gondwana-and Eurasia-derived continental fragments from each other.The belt contains ultramafic-ma...The Changning-Menglian Belt represents the main Paleo-Tethyan Suture in the southeastern Tibetan Plateau,which divides Gondwana-and Eurasia-derived continental fragments from each other.The belt contains ultramafic-mafic volcanic rocks that provide evidence of the tectonic processes which operated during the evolution of the Paleo-Tethyan Ocean.New geochemical data for Early Carboniferous volcanics in the southern Changning-Menglian Belt show that wehrlites have cumulate and poikilitic textures,and contain low-Fo(84.2-87.2)olivine,clinopyroxene with low Mg#values(79.4-85.6),and spinel with high Cr#values(67.8-72.4).Estimated equilibrium temperatures obtained using olivine-spinel Fe-Mg exchange geothermometry range from 978℃ to 1373℃(mean=1205℃;n=3).These observations combined with a lack of reaction or melt impregnation textures indicate that these units represent magmatic cumulates rather than having formed as a result of mantle-melt reactions.Both wehrlites and basalts in the belt have subparallel rare earth element(REE)-and primitive-mantle-normalized multi-element patterns with slightly positive Nb-Ta anomalies,but negligible Eu and Zr-Hf anomalies.The volcanics have similar Sr-Nd-Pb isotopic compositions withεNd(t)values of 4.2-4.5(mean=4.3;n=3)and 4.0-4.4(mean 4.2;n=4),respectively,and also have similar immobile element ratios,such as Nb/La,Nb/U,Th/La,Zr/Nb,Th/Ta,La/Yb,Nb/Th,Nb/Y,and Zr/Y.These characteristics indicate both units have ocean island basalt(OIB)-like geochemical affinities,consistent with the fact that the clinopyroxene in the wehrlites is compositionally similar to OIB-related cumulus clinopyroxene.This suggests that both the wehrlites and basalts were derived from similar parental magmas that underwent generally closed-system magmatic differentiation dominated by fractionation of the olivine and clinopyroxene.This parental magma was likely generated in an oceanic seamount setting from an OIB-type mantle source(i.e.,asthenospheric mantle)containing garnet-spinel lherzolite material.Combing this new data with that from oceanic seamount volcano-sedimentary suites derived from previous research enables the identification of a mature late Paleozoic ocean basin between the passive northeastern Gondwanan margin and the northward-migrating microcontinent of Lanping-Simao.展开更多
1 Introduction During the late Mesozoic times,the SE China is characterized by extensive magmatism and mineralization.The widely distributed granitoids with different(I-,S-and A-)types have been inferred to be closely...1 Introduction During the late Mesozoic times,the SE China is characterized by extensive magmatism and mineralization.The widely distributed granitoids with different(I-,S-and A-)types have been inferred to be closely related to the large-scale polymetallic mineralization.The Nanling tungsten-tin polymetallic belt is endowed with展开更多
The geological corridor of Western Liaoning province is an area of length 100 km and width 20 km and located in the eastern segment of northern margin of North China Craton(NCC),with the wide distribution of Mesozoic ...The geological corridor of Western Liaoning province is an area of length 100 km and width 20 km and located in the eastern segment of northern margin of North China Craton(NCC),with the wide distribution of Mesozoic granitic magmatism.It is the ideal area to study the granitic petrogenesis,the nature of magma source and the tectonic attribute.In this paper,we do the systematic researchesaboutthepetrology,geochronology,geochemistry and Zircon Hf isotopic of granitic rocks.Based on the mentioned above,we have built the geochronological framework and have discussed the petrogenesis,the nature of magma source and the tectonic setting of granitic rocks.And according to the information about the crust-mantle interaction recorded in granitic rocks and the regional data,we also discuss the relationship between Mesozoic granitic magma activities and lithosphere thinning,destruction of Craton mechanism in the eastern segment of northern margin of NCC.The Mesozoic granitic magma activities in The geological corridor of Western Liaoning province are divided into four stages(Fig.1):Late Triassic(230 Ma^228 Ma),early-middle Jurassic(194 Ma^169 Ma),Late Jurassic(161 Ma^155 Ma)and Early Cretaceous(139Ma^121 Ma).The late Triassic granitic rocks are composed of adamellite,monzogranite and diorite.The samples have high Sr,Cr,Ni content and low Yb,Y content,and the sample have high Mg#and high ratio of Sr/Y and La/Yb.The characteristics of inhomogenous negative value ofεHf(t)(-6.40^+0.19)in magmatic zircons and ancient crustal TDM2 values of 1.25 Ga^1.67 Ga(Fig.2),indicate that the Triassic granitic rocks were formed in a post-collisional extensional tectonic setting aftersubduction of Paleo-Asian Ocean and the subduction of Yangtze Craton,and they are the product of partial melting of ancient lower crust under the condition of the mantle-derived magma underplating,and geochemical features of the high Sr and low Y are inherited from the source of magma which is also enriched in Sr and depleted in Y.The geochemical features and assemblages of rocks formed during Jurassic-early Cretaceous are similar.The early-middle Jurassic granitic rocks are composed of syenogranite,monzogranite,quartz monzonite,granitic porphyry,granodiorite and quartz diorite.The late Jurassic granitic rocks are composed of monzogranite,granitic porphyry,and quartz diorite.The early Cretaceous granitic rocks are composed of monzogranite,quartz syenite,granitic porphyry,and quartz monzodiorite.The samples are characterized by the high SiO_2 content and total alkalis and are belonged to the high-K calc-alkaline series.And the characteristics of quasi-aluminous to weakly peraluminous(A/CNK<1.1,A/NK>1.0)and the negative relationship between P_2O_5and SiO_2 are similar to the characteristics of I-type granite.The samples are enriched in LREE contents and K,Pb and depleted in Nb,Ta,Ti and P.The characteristics of assemblage and geochemical features indicate the Jurassic-Cretaceous granitic rocks formed in the setting of active continental margin related to the subduction.The magmatic zircons of early-middle Jurassic granitic rocks have negativeεHf(t)(-16.60^-4.15)and ancient crustal TDM2 values of 1.49 Ga^2.28 Ga which indicates the primary magma is from the partial melting of ancient middle-lower crust(Fig.2).These rocks formed in the setting of active continental margin of subduction of Paleo-Pacific plate.The magma source of granitic rocks is from partial melting of the ancient lower-middle curst caused by the underplating of mantle magma,which formed in the condition of fluid derived from the dehydration of subducted slab affected on the lithosphere mantle.The magmatic zircons of late Jurassic granitic rocks have negativeεHf(t)(-26.24^-18.56)and ancient crustal TDM2 values of(2.39 Ga^2.87 Ga)which indicates the primary magma is from the partial melting of ancient upper-middle crust(Fig.2).And these rocks may be formed in the setting of active continental margin of intense subduction of Paleo-Pacific plate.In the intense subduction,the mantle magma is formed in the interaction of fluid derived from the dehydration of subducted slab with the lithosphere mantle,then further underplated the ancient middle-upper crust and make the ancient middle-upper curst partial melting.In this setting,the late Jurassic rocks are distributed widely in eastern North China.The samples in early Cretaceous have a wide range of values of Hf isotope:-24.92^-20.88(139 Ma),-4.72^+6.22(130 Ma),-17.30^-11.56(125 Ma^121 Ma),and the characteristics of Hf isotope indicate the source of earlyCretaceousmagma(middle-uppercrust,middle-lower crust or juvenile crust)is very complicated(Fig.2).The early Cretaceous granitic rocks were formed in the lithosphere extensional environment when the Paleo-Pacific plate subducted/roll-backed quickly in the direction of NNW with high angle.The regional extension made the asthenosphere upwell and be unstable,and the magma of mantle was formed.Then wide mantle-crust interactions make the crust partial melt,as a result,the source of early Cretaceous igneous rocks which are distributed widely in eastern North China Craton.The participation of depleted mantle components in the process of Late Triassic rock formation in western Liaoning area indicate the time of the lithosphere thinning in the eastern segment of northern margin of NCC begin from the late Triassic(~230 Ma).The double subduction of Paleo-Asian Ocean and Yangtze Craton in the early period is the reason of the lithosphere thinning.After the double subduction,the mantle-derived magma upwell and underplate the lithosphere mantle and lower crust in a post-collisional extensional tectonic setting.As a result,the lithosphere began to thin but the Craton destruction was not obviously in this period.The participation of depleted mantle components makes the continental crust slightly reforms and grows.The eastern segment of northern margin of NCC was in the setting of active continental margin in Jurassic,and the continuing dehydration and metasomatism of subduction slab changed the physical and chemical properties of the lithosphere mantle.The initial weak subduction in early-middle Jurassic makes the lithosphere become thin but no obvious destruction of Craton.And in this period,the continental crust reformed and grew slightly.As the subduction became stronger during late Jurassic,the thickness of lithosphere in eastern segment of northern margin of NCC become thinner and the destruction of Craton occurred locally and the continental crust reformed and grew to some extent.In early Cretaceous,the change of direction and angle of subduction of Paleo-Pacific led to the regional extension,which is the reason for massive mantle material upwelling and intense crust-mantle interaction.And the lithosphere thinning and destruction of Craton reached the peak.As a result,the effects of reconstruction and hyperplasia of continental crust are obviously.In our opinions,the underplating mechanism of mantle-derived magma occurred mainly in the initial stage(early Mesozoic)oflithosphere thinning,and the delamination of lithosphere mantle or lower crust coexisted while erosion action of mantle material occurred in the stage(late Mesozoic)of strong lithosphere thinning and destruction of Craton.展开更多
The Feidong district is located in the southern segment of the Tan-Lu fault zone that separates the South China Block(NCB)from the North China Craton(NCC).We report zircon U-Pb geochronology and Hf isotope data,as wel...The Feidong district is located in the southern segment of the Tan-Lu fault zone that separates the South China Block(NCB)from the North China Craton(NCC).We report zircon U-Pb geochronology and Hf isotope data,as well as whole-rock geochemistry for Xishanyi granodiorite and Jianshan granite in the Feidong district.Zircon U-Pb dating results show that the emplacement ages of the Xishanyi and Jianshan intrusions are 124±3 Ma and 130±1 Ma respectively,coeval with magmatic events linked to large-scale lithospheric thinning in eastern China.The whole-rock geochemistry of the Xishanyi and Jianshan intrusions demonstrate that they are peraluminous,high potassium calc-alkaline I-type granites with adakitic characteristics.Both intrusions underwent weak crustal assimilation during emplacement.The in situ zirconε(Hf)(t)values of the Xishanyi granodiorites range from-26.4 to-21.8,with T(DM2)model ages of 2552 to 2841 Ma.The in situ zirconε(Hf)(t)values of the Jianshan granite are from-27.5 to-23.0 with T(DM2)model ages of 2632 to 2904 Ma.The peak age of inherited zircon grains from the Xishanyi granodiorite and the Jianshan granite were^2.07 Ga and^1.94 Ga,respectively.After compared with the regional magmatism,we suggest that both the Xishanyi and Jianshan granitoid intrusions were derived from partial melting of the NCC lower crust.展开更多
1 Introduction Voluminous Mesozoic magmatic rocks containing abundant Au-Mo polymetallic mineralization resources are developed in the Xiaoqinling-Xiong’ershan district of the southern margin of the North China Crato...1 Introduction Voluminous Mesozoic magmatic rocks containing abundant Au-Mo polymetallic mineralization resources are developed in the Xiaoqinling-Xiong’ershan district of the southern margin of the North China Craton(NCC).展开更多
1 Introduction The western Kunlun orogen,located in the northwest Tibet Plateau,and is a conjunction between the Pan-Asian and the Tethys tectonic domains.From north to south,the Western Kunlun orogen includes
Objective The widely exposed granites in the Wulashan area of Inner Mongolia are an important component of intermediate-acidic magma belt at the northern margin of the North China Craton,and are also a natural laborat...Objective The widely exposed granites in the Wulashan area of Inner Mongolia are an important component of intermediate-acidic magma belt at the northern margin of the North China Craton,and are also a natural laboratory to research the origin of granite bodies.The Shadegai pluton,a representative intrusion,intruded into the Wulashan Group metamorphic rocks,occurring as stock,展开更多
The Cretaceous Ambohiby Complex is an alkaline ring complex located in the west central part of Madagascar and covers a mountainous area of approximate 225 km^2.The complex intrudes into Precambrian basement gneisses ...The Cretaceous Ambohiby Complex is an alkaline ring complex located in the west central part of Madagascar and covers a mountainous area of approximate 225 km^2.The complex intrudes into Precambrian basement gneisses and is dominated by alkaline mafic to felsic rocks with sodic mineralogies. Pyroxenes are generally aegirine,aegirine-augite,and hedenbergite and commonly occur in granites,展开更多
The Cenozoic volcanic rocks in the Yumen and Hoh Xil area formed in the intracontinental orogenic belt, which primary magma originated from a particular enrichment upmantle and accreted crust\|mantle belt or directly ...The Cenozoic volcanic rocks in the Yumen and Hoh Xil area formed in the intracontinental orogenic belt, which primary magma originated from a particular enrichment upmantle and accreted crust\|mantle belt or directly originated from asthenosphere superface by partial melting of pyrolite.Through the deeply study of the Cenozoic volcanic rocks, the effective petrological constraints on the deep\|internal geology process can be obtained. And of course, it is the window for discussion the orogeny/uplift machinism of the Qinghai—Tibet plateau.1\ Brief regional geology\;The Yumen Cenozoic volcanic rock lithodistrict belongs to the north margin of Qinghai—Tibet plateau. This lithodistrict mainly consists of Hongliuxia and Hanxia volcanic rock bodies. The Hongliuxia Pleistocene epoch volcano neck is located to the northwest of Yumen City about 40km away, consisted of tephrite and trachybasalt. The boundary line between the volcano neck and the country rocks well defined and the contact plane is almost erect. The drag structure and wrinkle have been identified in the country rocks, which were due to the upthrusting of the magma. About 100 meters away to the south of the volcano neck, there is a basaltic flowage which covers on the Cretaceous—Tertiary shale and argillaceous sandstone.The Hanxia Cenozoic volcanic rock lithodistrict is located to the west of Yumen City about 15km away, which is a river valley extending into the north piedmont of Qilian Mountain. It dissected the Cretaceous—Tertiarystratigraphic sequence. The Cenozoic volcanic rock distributed in the Hanxia river valley is a lava flowage and NWW\|trending as a long lava dome.The Hoh Xil Cenozoic volcanic rock lithodistrict is located in the north part of Qinghai—Tibet plateau. The Cenozoic intensely intracontinental volcanism in this region had formed a number of lava sheets and subvolcanic rock bodies which were in different size and now present as lava platforms with about an elevation of 5000 meters. Affected by the preexisting NWW\|trending structure zones, there formed several NWW\|trending active\|volcano zones in the area during the Cenozoic era when the magma overflowed and/or intruded near to th e ground surface.展开更多
The grey gneisses are composed of early-stage layered TTG and late-stage diapiric tonalite in-trusions.The Dabie complex,northeastern Hubei Province,may be distinguished into supracrustal sequenceand grey gneisses.Dif...The grey gneisses are composed of early-stage layered TTG and late-stage diapiric tonalite in-trusions.The Dabie complex,northeastern Hubei Province,may be distinguished into supracrustal sequenceand grey gneisses.Different distribution patterns of rare earth elements in the early- and late- stage gneisses,i.e.the early-stage gneisses are enriched in LREE and remarkably depleted in HREE;and late-stage isslightly enriched in LREE and unevidently depleted in HREE.Geological evidence and characteristics of el-ement ratio diagrams suggest that the TTG is mainly controlled by portional partial melting and accompa-nied with fractional crystallization.The quantitative modelling of REE pattern indicates that TTG is formedfrom amphibolite transformed from basic rocks with 25%～65% of portional partial melt while thelate-stage tonalite intrusion was also accompanied with fractional crystalization of 22% biotites.展开更多
基金funded by Gansu Provincial Natural Science Foundation (Grant Numbers 21JR7RA503 and22JR5RA819)the Fundamental Research Funds for the Central Universities (Grant lzujbky-2021-ct07)+1 种基金the Key Talent Project of Gansu Province (2022-Yangzhenxi)the National Second Expedition to the Tibetan Plateau (2019QZKK0704)。
文摘Geodynamic mechanism responsible for the generation of Silurian granitoids and the tectonic evolution of the Qilian orogenic belt remains controversial. In this study, we report the results of zircon U–Pb age, and systematic whole-rock geochemical data for the Haoquangou and Liujiaxia granitoids within the North Qilian orogenic belt and the Qilian Block, respectively, to constrain their petrogenesis, and the Silurian tectonic evolution of the Qilian orogenic belt. Zircon U–Pb ages indicate that the Haoquangou and Liujiaxia intrusions were emplaced at423 ± 3 Ma and 432 ± 4 Ma, respectively. The Haoquangou granodiorites are calc-alkaline, while the Liujiaxia granites belong to the high-K calc-alkaline series.Both are peraluminous in composition and have relatively depleted Nd isotopic [ε_(Nd)(t) =(-3.9 – + 0.6)] characteristics compared with regional basement rocks, implying their derivation from a juvenile lower crust. They show adakitic geochemical characteristics and were generated by partial melting of thickened lower continental crust. Postcollisional extensional regime related to lithospheric delamination was the most likely geodynamic mechanism for the generation of the Haoquangou granodiorite, while the Liujiaxia granites were generated in a compressive setting during continental collision between the Qaidam and Qilian blocks.
基金supported by the National Natural Science Foundation of China Program(Grant Nos.41672072,41302074)the Third Xinjiang Scientific Expedition Program(Grant No.2021xjkk1301)。
文摘The Xiaobaishitou gabbro-diorite pluton comprises a medium-grained gabbro-diorite suite and a fine-grained diorite suite,which intrude the Kawabulag Group in the East Tianshan Orogen of the Central Asian Orogenic Belt(CAOB).A combination of mineral chemistry,zircon U-Pb age,whole-rock geochemistry,Sr-Nd isotopes,and in situ zircon Hf isotopes for newly found gabbro-diorite from the Xiaobaishitou district in the Central Tianshan Terrane(CTT)is presented to investigate the petrogenesis and tectonic or even crustal evolution of the East Tianshan Orogen.Laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS)zircon U-Pb analyses indicate that the gabbro-diorite was formed at 324.7±2.4 Ma.The isolated clinopyroxene formed under higher P-T-fO_(2)melt conditions(10.7–14.6 kbar;1199–1269℃;high fO_(2))than those for the hornblende,plagioclase,and zircon(557–687℃;moderate fO_(2))in the gabbro-diorite,which reveals a multilevel,magmatic storage system.The gabbro-diorite is characterized by fractioned REE patterns,enriched LILEs(e.g.,Ba and Pb),negative anomalies of HFSEs(e.g.,Nb and Ta),and low La/Yb and Sr/Y ratios,which are typically indicative of crustal contamination and accounted for by subduction-related fluids.The rock also characterized by typical features of high compatible elements(MgO=3.14–11.65 wt%,Cr=1–157 ppm,Ni=6–830 ppm),high Mg^(#)(47–74),positiveε_(Hf)(t)values(+5.1 to+10.3)andε_(Nd)(t)values(+2.3 to+4.4).These features suggest that the Xiaobaishitou gabbro-diorite was most likely derived from metasomatic mantle and contaminated minor crustal components.Taking into account the spatial and temporal distribution of the Carboniferous magmatic rocks in the CTT,we suggest the formation of the Xiaobaishitou gabbro-diorite was attributed to southward subduction of the Kangguer Ocean.
基金jointly supported by National Key Research and Development Program of China(Grant No.2022YFC2905002)Special Scientific Research Fund of Tibet Bureau of Geology and Mineral Exploration and Development(Grant No.202119)+2 种基金National Natural Science Foundation of China(Grant No.41902101)Research Start-up Fund of Chengdu University of Technology(Grant No.10912-KYQD2020-08395)the Opening Foundation of MNR Key Laboratory of Metallogeny and Mineral Assessment(Grant No.ZS2101)。
文摘The Bangbule skarn lead-zinc(Pb-Zn)deposit(>1 Mt Zn+Pb)is located in the western Nyainqentanglha polymetallic metallogenetic belt,central Tibet.Lenticular orebodies are all hosted in skarn and developed in the contact zone between the quartz porphyry and carbonate strata of the mid Paleozoic Middle to Upper Chaguoluoma Formation as well as in carbonate and sandstone beds of the Upper Paleozoic Laga Formation.As a newly discovered skarn deposit,the geological background and metallogenesis of this deposit remain poorly understood.Detailed petrological,geochemical and geochronological data of the ore-related quartz porphyry,helps constrain the mineralization age and contributes to discussion on the ore genesis of the Bangbule deposit.Both endoskarn and exoskarn are identified in the Bangbule deposit.From quartz porphyry to carbonate formation,the exoskarn is zoned from proximal garnet skarn to distal pyroxene skarn.Zircon U-Pb dating results show that the quartz porphyry formed at 73.9±0.8 Ma.Geochemical analysis results show that the quartz porphyry has high contents of SiO_(2)(71.40–74.94 wt%)and K_(2)O+Na_(2)O(3.76–8.46 wt%)with A/CNK values of 0.69 to 1.06.Besides,the quartz porphyry is enriched in large ion lithophile elements(LILEs)and light rare earth elements(LREEs)and have lowεNd(t)(from-8.25 to-8.19)and high initial(^(87)Sr/^(86)Sr)i values(0.713611–0.714478).Major,trace elements and whole-rock F concentration analysis results from the endoskarn samples show higher TFe_(2)O_(3),MgO,CaO,Pb+Zn,W,Sn,Mo and F etc.,and lower alkalis(K_(2)O,Na_(2)O,Sr and Ba)than those of fresh quartz porphyry,indicating that the early ore-forming fluids were an Ca-Fe-F-enriched fluid.Massive ore in the proximal skarn might be related to the high F content in the magma,which lowered the solidus temperature of the quartz porphyry magma and caused a lower temperature of the ore-forming fluids,as well as facilitating the precipitation of sphalerite and galena.Based on the geochemical characteristics presented in this study,we propose that the ore-related quartz porphyry was formed by partial melting of crust materials with some juvenile crustal component input.The partial melting of the middle-upper crust after the initial enrichment of lead and zinc elements are important for the formation of Pb-Zn deposits.The case study of the Bangbule deposit has proven that there is still a crust-derived magmatic source region in the western segment of the central Lhasa terrane.Therefore,there is still great potential for Pb-Zn mineralization and Pb-Zn exploration.
文摘The Rb-Sr whole-rock isochron,age 1636±66 Ma of Mirgarani granite,is the one of the oldest granite dated in the northwestern part of the Chhotanagpur Granite Gneiss Complex(CGGC).The initial Sr ratio is 0.715±0.012(MSWD=0.11),showing an S-type affinity.The Mirgarani granite has intruded the migmatite complex of the Dudhi Group and forms the Mirgarani formation comparable to the granites of the Bihar Mica Belt around Hazaribagh(1590±30 Ma).The present studies have established the chronostratigraphy of the Dudhi Group and adjoining areas in CGGC.Petro-graphic and geochemical studies revealed that the granite is enriched in Rb(271 ppm),Pb(77 ppm),Th(25 ppm),and U(33 ppm)and depleted in Sr(95 ppm),Nb(16 ppm),Ba(399 ppm)and Zr(143 ppm)contents as compared to the normal granite.The Mirgarani granite is a peraluminous(A/CNK=1.23),high potassic(K_(2)O 6.42%),Calc-Alkalic to Alkali-Calcic{(Na_(2)O+K_(2)O)-CaO=6.29}S-Type granite,a feature supported by the presence of modal garnet and normative corundum(2.68%).The Mirgarani granite is considered to have been formed by the anatexis of a crustal sedimentary protolith at a depth of approximately 30 km with temperatures ranging from 685-700℃ during the Co-lumbian-Nuna Supercontinent.
基金financially supported by the National Natural Science Foundation of China (Grants 41330206)National Key Basic Research Program of China (2013CB429803)
文摘The Songnen–Zhangguangcai Range Massif(SZRM)is located in the eastern Central Asian Orogenic Belt and crops out over an extensive part of NE China.The massif was originally thought to contain numerous Precambrian terranes(e.g.,Xingdong,Dongfengshan,Yimianpo and Zhangguangcailing groups).However,more recent zircon U–Pb dating indicates that the majority of these so-called Precambrian sedimentary and igneous rocks actually formed during either the Paleozoic or Mesozoic and contain only minor Precambrian components(Wang et al.,2014).The presence of Neoproterozoic and Paleoproterozoic detrital zircons with magmatic origins from and Paleozoic units of the SZRM indicating that this area occurs Proterozoic magmatism(Wang et al.,2014),whereas no Proterozoic magmastism has been found.Recently,Pei et al.(2007)reported the ca.1800Ma magmastism,as evidenced by the data of exploration drillholes in the southern Songliao basin.However,an alternative view is that the basement within the SZRM is predominantly Phanerozoic,as evidenced by the presence of Paleozoic fossils and comparatively rare geochronological data(Guo and Liu,1985;Wu et al.,2011),meaning that the ca.1800 Ma rocks in this area may be a tectonically emplaced slice of the North China Craton(Zhang et al.,2005).All of this means that the age and nature of the SZRM basement,and whether this area records Neoproterozoic magmatism,remain unclear.This study presents new geochronological,whole-rock geochemical,and zircon Hf isotopic data for early Proterozoic granitoids within the eastern margin of the SZRM of NE China.These data provide insights into the Neoproterozoic tectonic setting of the SZRM and the links between this magmatism and the evolution of the Rodinia supercontinent.The zircon U–Pb dating indicates that the Neoproterozoic magmatism within the SZRM can be subdivided into two stages:(1)a^917–911 Ma suite of syenogranites and monzogranites,and(2)an^841 Ma suite of granodiorites.The 917–911 Ma granitoids contain high concentrations of Si O2(67.89–71.18 wt.%),K2O(4.24–6.91 wt.%),and Al2O3(14.89–16.14 wt.%),and low concentrations of TFe2O3(1.63–3.70 wt.%)and Mg O(0.53–0.88 wt.%).They are enriched in the light rare earth elements(LREE)and the light ion lithophile elements(LILE),are depleted in the heavy REE(HREE)and the heavy field strength elements(HFSE;e.g.,Nb,Ta,and Ti),and have slightly positive Eu anomalies,indicating they are geochemically similar to high-K adakitic rocks.They have zirconεHf(t)values and TDM2 ages from–4.4 to+1.5and from 1915 Ma to 1592 Ma,respectively,suggesting they were derived from a primary magma generated by the partial melting of ancient thickened lower crustal material.In comparison,the 841 Ma granodiorites contain relatively low concentrations of Al2O3(14.50–14.58 wt.%)and K2O(3.27–3.29 wt.%),relatively high concentrations of TFe2O3(3.78–3.81 wt.%)and the HREE,have negative Eu anomalies,and have zirconεHf(t)values and TDM2ages from–4.7 to+1.0 and from 1875 to 1559 Ma,respectively.These granodiorites formed from a primary magma generated by the partial melting of ancient crustal material.The^917–911 Ma magmatism within the SZRM is inferred to have formed in an orogenic setting,whereas the^841 Ma magmatism formed in an anorogenic setting related to either a post-orogenic tectonic event or the onset of Neoproterozoic continental rifting.It is proposed that the microcontinental massifs within the SZRM formed during or following the final stage of assembly of Rodinia before rifting away from the Tarim Craton in response to Rodinia breakup.
基金supported by 973 (2012CB416601) and NFSC (41322018) projects
文摘It is well known that there are widespread igneous events at^2100 Ma in the Eastern North China Craton;however,their tectonic environments are controversial.They were thought to be either related to an intra-continental rifting
基金financially supported by the National Natural Science Foundation of China(grant No.41502076)the Science Research Fund of Yunnan Provincial Education Department(grant No.2015Y066)+1 种基金the Provincial People Training Program of Kunming University of Science and Technology(grant No.KKSY201421042)the Project of China Geological Survey(grant No.12120114013701)
文摘Objective The Late Cretaceous Xiuwacu ore-bearing porphyry is located in the Geza area of southern Yidun arc,SW China.In this area,the rock mass is mainly composed of three lithofacies:biotite granite porphyry,monzonitic
基金financially supported by projects of the China Geological Survey (Grant Nos. 1212011220458, 1212011220492)
文摘We performed geochronological and geochemical analyses of the A-type granite in the Hongol area, central Inner Mongolia, to determine its age, petrogenesis and tectonic setting, which are significant for clarifying the Late Paleozoic tectonic evolution of the Xing'an Mongolian Orogenic Belt(XMOB). The rock type of the A-type granite in the Hongol area is alkali-feldspar granite, and it constitutes a western part of the Baiyinwula-Dongujimqin A-type granite belt. Zircon U-Pb geochronology yields ^(206)Pb/^(238)U ages ranging from 293 to 286 Ma for the alkali-feldspar granite, indicating this granitic pluton formed in the Early Permian. The alkali-feldspar granite is high in silica(SiO_2=75.13 wt%-80.17 wt%), aluminum(Al_2 O_3=10.59 wt%-13.17 wt%) and alkali(Na_2 O+K_2 O=7.33 wt%-9.11 wt%), and low in MgO(0.08 wt%-0.39 wt%) and CaO(0.19 wt%-0.70 wt%). It is obviously enriched in LILEs such as Rb, Th and K,depleted in HFSEs such as Nb, Ti, La and Ce, with pronounced negative anomalies of Nb, Ti, P, Eu, Sr and Ba. Its Sr-Nd-Pb isotopic compositions show positive ε_(Nd)(t)(+0.72-+3.08), low T_(DM2)(805-997 Ma),and high radioactive Pb with(^(206)Pb/^(204)Pb)_i of 18.710-19.304,(^(207)Pb/^(204)Pb)_i of 15.557-15.604 and(^(208)Pb/^(204)Pb)_i of 37.887-38.330. Petrological characteristics and geochemical data suggest that the alkalifeldspar granite in the Hongol area belongs to aluminous A-type granite. This A-type granite formed in a post-collisional extensional setting and was generated by the partial melting of felsic rocks in the middlelower crust resulting from post-collisional slab breakoff. It is suggested that the Paleo-Asian Ocean was closed before the Permian in central Inner Mongolia.
基金the financial support provided by the open fund from the Key Laboratory of Deep-Earth Dynamics of the Ministry of Natural Resources, Institute of Geology, as well as Chinese Academy of Geological Sciences (Grant No. J1901-16)the State Key Laboratory for Mineral Deposits Research, Nanjing University (Grant No. 2020-LAMD-K04)+1 种基金the National Natural Science Foundation of China (Grant No. 41403029)The support provided by the China Scholarship Council (CSC) during a visit to the University of Arizona (201709110012)。
文摘The Cenozoic geological hallmark of Western Yunnan is the characteristic voluminous Late Cretaceous-Eocene granites;however, their geological background and petrogenesis have not been well constrained and elucidated. In this study, we present new zircon U-Pb dating, along with geochemical and Sr-Nd-Hf isotopic data for granites from the Tengchong–Lianghe granitoid belt(as abbreviated to Tengliang belt) and West Yingjiang batholiths from the Tengchong block. The mineralogical and geochemical features of the Tengliang granites and the West Yingjiang batholiths are ascribed to aluminous S-type granites and weak peraluminous I-type, respectively. Zircon U-Pb analyses yielded consistent ages ranging from 67.5 Ma, 68.4 Ma and 66.2 Ma from the Tengliang granitoid belt and 50.4 Ma to 60.8 Ma for three samples from the west Yingjiang batholiths. The Tengliang granites were emplaced during the Late Cretaceous(68-66 Ma) and demonstrate negative ε_(Hf)(t) values(-24 to-4) and initial ~(87)Sr/~(86)Sr ratios of 0.7101–0.7139 and significant negative ε_(Nd)(t) values from-8.91 to-13.2, indicating a Proterozoic sedimentary source or enriched components. The hornblende-bearing I-type granites from West Yingjiang are characterized by lower initial ~(87)Sr/~(86)Sr ratios of 0.7076–0.7106, compared to Tengliang granite and negative whole-rock ε_(Nd)(t) values from-4.0 to-11.9. The early Eocene west Yingjiang gneissic granites show wide ranges of ε_(Hf)(t) values from +7.4 to-8.5 and T_(2DM) of 1.30–0.65 Ga, indicating partial melting of ancient crust with contributions of depleted mantle materials. In combination with the regional background and previous studies, we propose that such a spatio-temporal distribution of the Tengchong granitoid belt might be related to the rollback or angleswitching of the Neo-Tethyan subducting slab. This study sheds new light on the evolutionary history of the Tengchong block.
基金supported financially by the NSFC projects (U1403291, 41830216, and 41802074)projects of the China Geological Survey (Nos. DD20160024, DD20160123, and DD20160345)
文摘Carboniferous magmatism is one of the most important tectonothermal events in the Central Asian Orogenic Belt(CAOB). However, the final closure time of the Kalamaili Ocean between East Junggar and Harlik Mountain is still debated. Early Carboniferous(332 Ma) and late Carboniferous(307-298 Ma) granitic magmatism from Kalamaili fault zone have been recognized by LA-ICP-MS zircon U-Pb dating. They are both metaluminous highly fractionated I-type and belong to the high-K calc-alkaline. The granitoids for early Carboniferous have zircon εHf(t) values of-5.1 to +8.5 with Hf model ages(TDM2) of 1.78-0.83 Ga, suggesting a mixed magma source of juvenile material with old continental crust. Furthermore, those for late Carboniferous have much younger heterogeneous zircon εHf(t) values(+5.1 to +13.6) with Hf model ages(TDM2=1.03-0.45 Ga) that are also indicative of juvenile components with a small involvement of old continental crust. Based on whole-rock geochemical and zircon isotopic features, these high-K granitoids were derived from melting of heterogeneous crustal sources or through mixing of old continental crust with juvenile components and minor AFC(assimilation and fractional crystallization). The juvenile components probably originated from underplated basaltic magmas in response to asthenospheric upwelling. These Carboniferous highly fractionated granites in the Kalamaili fault zone were probably emplaced in a post-collisional extensional setting and suggested vertical continental crustal growth in the southern CAOB, which is the same or like most granitoids in CAOB. This study provides new evidence for determining the post-accretionary evolution of the southern CAOB. In combination with data from other granitoids in these two terranes, the Early Carboniferous Heiguniangshan pluton represents the initial record of post-collisional environment, suggesting that the final collision between the East Junggar and Harlik Mountain might have occurred before 332 Ma.
基金This study was financially supported by the Major Science and Technology Special Plan of Yunnan Province(Grant No.202202AG050006)the National Natural Science Foundation of China(Grant No.41603032)+1 种基金the Applied Basic Research Foundation of Yunnan Province(Grant No.2017FB075)the Yunnan Key Research and Development Program(Grant No.2015CB452601),and the China Geological Survey(Grant No.12120114064301).
文摘The Changning-Menglian Belt represents the main Paleo-Tethyan Suture in the southeastern Tibetan Plateau,which divides Gondwana-and Eurasia-derived continental fragments from each other.The belt contains ultramafic-mafic volcanic rocks that provide evidence of the tectonic processes which operated during the evolution of the Paleo-Tethyan Ocean.New geochemical data for Early Carboniferous volcanics in the southern Changning-Menglian Belt show that wehrlites have cumulate and poikilitic textures,and contain low-Fo(84.2-87.2)olivine,clinopyroxene with low Mg#values(79.4-85.6),and spinel with high Cr#values(67.8-72.4).Estimated equilibrium temperatures obtained using olivine-spinel Fe-Mg exchange geothermometry range from 978℃ to 1373℃(mean=1205℃;n=3).These observations combined with a lack of reaction or melt impregnation textures indicate that these units represent magmatic cumulates rather than having formed as a result of mantle-melt reactions.Both wehrlites and basalts in the belt have subparallel rare earth element(REE)-and primitive-mantle-normalized multi-element patterns with slightly positive Nb-Ta anomalies,but negligible Eu and Zr-Hf anomalies.The volcanics have similar Sr-Nd-Pb isotopic compositions withεNd(t)values of 4.2-4.5(mean=4.3;n=3)and 4.0-4.4(mean 4.2;n=4),respectively,and also have similar immobile element ratios,such as Nb/La,Nb/U,Th/La,Zr/Nb,Th/Ta,La/Yb,Nb/Th,Nb/Y,and Zr/Y.These characteristics indicate both units have ocean island basalt(OIB)-like geochemical affinities,consistent with the fact that the clinopyroxene in the wehrlites is compositionally similar to OIB-related cumulus clinopyroxene.This suggests that both the wehrlites and basalts were derived from similar parental magmas that underwent generally closed-system magmatic differentiation dominated by fractionation of the olivine and clinopyroxene.This parental magma was likely generated in an oceanic seamount setting from an OIB-type mantle source(i.e.,asthenospheric mantle)containing garnet-spinel lherzolite material.Combing this new data with that from oceanic seamount volcano-sedimentary suites derived from previous research enables the identification of a mature late Paleozoic ocean basin between the passive northeastern Gondwanan margin and the northward-migrating microcontinent of Lanping-Simao.
基金Funding for the project is provided by the China Geological Survey(NO. 121201004000150015 and NO. 12120115037101)
文摘1 Introduction During the late Mesozoic times,the SE China is characterized by extensive magmatism and mineralization.The widely distributed granitoids with different(I-,S-and A-)types have been inferred to be closely related to the large-scale polymetallic mineralization.The Nanling tungsten-tin polymetallic belt is endowed with
文摘The geological corridor of Western Liaoning province is an area of length 100 km and width 20 km and located in the eastern segment of northern margin of North China Craton(NCC),with the wide distribution of Mesozoic granitic magmatism.It is the ideal area to study the granitic petrogenesis,the nature of magma source and the tectonic attribute.In this paper,we do the systematic researchesaboutthepetrology,geochronology,geochemistry and Zircon Hf isotopic of granitic rocks.Based on the mentioned above,we have built the geochronological framework and have discussed the petrogenesis,the nature of magma source and the tectonic setting of granitic rocks.And according to the information about the crust-mantle interaction recorded in granitic rocks and the regional data,we also discuss the relationship between Mesozoic granitic magma activities and lithosphere thinning,destruction of Craton mechanism in the eastern segment of northern margin of NCC.The Mesozoic granitic magma activities in The geological corridor of Western Liaoning province are divided into four stages(Fig.1):Late Triassic(230 Ma^228 Ma),early-middle Jurassic(194 Ma^169 Ma),Late Jurassic(161 Ma^155 Ma)and Early Cretaceous(139Ma^121 Ma).The late Triassic granitic rocks are composed of adamellite,monzogranite and diorite.The samples have high Sr,Cr,Ni content and low Yb,Y content,and the sample have high Mg#and high ratio of Sr/Y and La/Yb.The characteristics of inhomogenous negative value ofεHf(t)(-6.40^+0.19)in magmatic zircons and ancient crustal TDM2 values of 1.25 Ga^1.67 Ga(Fig.2),indicate that the Triassic granitic rocks were formed in a post-collisional extensional tectonic setting aftersubduction of Paleo-Asian Ocean and the subduction of Yangtze Craton,and they are the product of partial melting of ancient lower crust under the condition of the mantle-derived magma underplating,and geochemical features of the high Sr and low Y are inherited from the source of magma which is also enriched in Sr and depleted in Y.The geochemical features and assemblages of rocks formed during Jurassic-early Cretaceous are similar.The early-middle Jurassic granitic rocks are composed of syenogranite,monzogranite,quartz monzonite,granitic porphyry,granodiorite and quartz diorite.The late Jurassic granitic rocks are composed of monzogranite,granitic porphyry,and quartz diorite.The early Cretaceous granitic rocks are composed of monzogranite,quartz syenite,granitic porphyry,and quartz monzodiorite.The samples are characterized by the high SiO_2 content and total alkalis and are belonged to the high-K calc-alkaline series.And the characteristics of quasi-aluminous to weakly peraluminous(A/CNK<1.1,A/NK>1.0)and the negative relationship between P_2O_5and SiO_2 are similar to the characteristics of I-type granite.The samples are enriched in LREE contents and K,Pb and depleted in Nb,Ta,Ti and P.The characteristics of assemblage and geochemical features indicate the Jurassic-Cretaceous granitic rocks formed in the setting of active continental margin related to the subduction.The magmatic zircons of early-middle Jurassic granitic rocks have negativeεHf(t)(-16.60^-4.15)and ancient crustal TDM2 values of 1.49 Ga^2.28 Ga which indicates the primary magma is from the partial melting of ancient middle-lower crust(Fig.2).These rocks formed in the setting of active continental margin of subduction of Paleo-Pacific plate.The magma source of granitic rocks is from partial melting of the ancient lower-middle curst caused by the underplating of mantle magma,which formed in the condition of fluid derived from the dehydration of subducted slab affected on the lithosphere mantle.The magmatic zircons of late Jurassic granitic rocks have negativeεHf(t)(-26.24^-18.56)and ancient crustal TDM2 values of(2.39 Ga^2.87 Ga)which indicates the primary magma is from the partial melting of ancient upper-middle crust(Fig.2).And these rocks may be formed in the setting of active continental margin of intense subduction of Paleo-Pacific plate.In the intense subduction,the mantle magma is formed in the interaction of fluid derived from the dehydration of subducted slab with the lithosphere mantle,then further underplated the ancient middle-upper crust and make the ancient middle-upper curst partial melting.In this setting,the late Jurassic rocks are distributed widely in eastern North China.The samples in early Cretaceous have a wide range of values of Hf isotope:-24.92^-20.88(139 Ma),-4.72^+6.22(130 Ma),-17.30^-11.56(125 Ma^121 Ma),and the characteristics of Hf isotope indicate the source of earlyCretaceousmagma(middle-uppercrust,middle-lower crust or juvenile crust)is very complicated(Fig.2).The early Cretaceous granitic rocks were formed in the lithosphere extensional environment when the Paleo-Pacific plate subducted/roll-backed quickly in the direction of NNW with high angle.The regional extension made the asthenosphere upwell and be unstable,and the magma of mantle was formed.Then wide mantle-crust interactions make the crust partial melt,as a result,the source of early Cretaceous igneous rocks which are distributed widely in eastern North China Craton.The participation of depleted mantle components in the process of Late Triassic rock formation in western Liaoning area indicate the time of the lithosphere thinning in the eastern segment of northern margin of NCC begin from the late Triassic(~230 Ma).The double subduction of Paleo-Asian Ocean and Yangtze Craton in the early period is the reason of the lithosphere thinning.After the double subduction,the mantle-derived magma upwell and underplate the lithosphere mantle and lower crust in a post-collisional extensional tectonic setting.As a result,the lithosphere began to thin but the Craton destruction was not obviously in this period.The participation of depleted mantle components makes the continental crust slightly reforms and grows.The eastern segment of northern margin of NCC was in the setting of active continental margin in Jurassic,and the continuing dehydration and metasomatism of subduction slab changed the physical and chemical properties of the lithosphere mantle.The initial weak subduction in early-middle Jurassic makes the lithosphere become thin but no obvious destruction of Craton.And in this period,the continental crust reformed and grew slightly.As the subduction became stronger during late Jurassic,the thickness of lithosphere in eastern segment of northern margin of NCC become thinner and the destruction of Craton occurred locally and the continental crust reformed and grew to some extent.In early Cretaceous,the change of direction and angle of subduction of Paleo-Pacific led to the regional extension,which is the reason for massive mantle material upwelling and intense crust-mantle interaction.And the lithosphere thinning and destruction of Craton reached the peak.As a result,the effects of reconstruction and hyperplasia of continental crust are obviously.In our opinions,the underplating mechanism of mantle-derived magma occurred mainly in the initial stage(early Mesozoic)oflithosphere thinning,and the delamination of lithosphere mantle or lower crust coexisted while erosion action of mantle material occurred in the stage(late Mesozoic)of strong lithosphere thinning and destruction of Craton.
基金sponsored by the National Key Research and Development Program(2016YFC0600206)the Natural Science Foundation of China(41972076,91962218)the Structural Characteristics and Evolution of the Southern Segment of the Tan-Lu Fault Zone(DD20190043)。
文摘The Feidong district is located in the southern segment of the Tan-Lu fault zone that separates the South China Block(NCB)from the North China Craton(NCC).We report zircon U-Pb geochronology and Hf isotope data,as well as whole-rock geochemistry for Xishanyi granodiorite and Jianshan granite in the Feidong district.Zircon U-Pb dating results show that the emplacement ages of the Xishanyi and Jianshan intrusions are 124±3 Ma and 130±1 Ma respectively,coeval with magmatic events linked to large-scale lithospheric thinning in eastern China.The whole-rock geochemistry of the Xishanyi and Jianshan intrusions demonstrate that they are peraluminous,high potassium calc-alkaline I-type granites with adakitic characteristics.Both intrusions underwent weak crustal assimilation during emplacement.The in situ zirconε(Hf)(t)values of the Xishanyi granodiorites range from-26.4 to-21.8,with T(DM2)model ages of 2552 to 2841 Ma.The in situ zirconε(Hf)(t)values of the Jianshan granite are from-27.5 to-23.0 with T(DM2)model ages of 2632 to 2904 Ma.The peak age of inherited zircon grains from the Xishanyi granodiorite and the Jianshan granite were^2.07 Ga and^1.94 Ga,respectively.After compared with the regional magmatism,we suggest that both the Xishanyi and Jianshan granitoid intrusions were derived from partial melting of the NCC lower crust.
基金supported by the NSFC (41373039)the DREAM project of MOST, China (2016YFC0600403)
文摘1 Introduction Voluminous Mesozoic magmatic rocks containing abundant Au-Mo polymetallic mineralization resources are developed in the Xiaoqinling-Xiong’ershan district of the southern margin of the North China Craton(NCC).
基金funded by the State Technology Support Program(2015BAB05B03-02)
文摘1 Introduction The western Kunlun orogen,located in the northwest Tibet Plateau,and is a conjunction between the Pan-Asian and the Tethys tectonic domains.From north to south,the Western Kunlun orogen includes
基金funded by the National Natural Science Foundation of China(grant No.41302064)
文摘Objective The widely exposed granites in the Wulashan area of Inner Mongolia are an important component of intermediate-acidic magma belt at the northern margin of the North China Craton,and are also a natural laboratory to research the origin of granite bodies.The Shadegai pluton,a representative intrusion,intruded into the Wulashan Group metamorphic rocks,occurring as stock,
文摘The Cretaceous Ambohiby Complex is an alkaline ring complex located in the west central part of Madagascar and covers a mountainous area of approximate 225 km^2.The complex intrudes into Precambrian basement gneisses and is dominated by alkaline mafic to felsic rocks with sodic mineralogies. Pyroxenes are generally aegirine,aegirine-augite,and hedenbergite and commonly occur in granites,
文摘The Cenozoic volcanic rocks in the Yumen and Hoh Xil area formed in the intracontinental orogenic belt, which primary magma originated from a particular enrichment upmantle and accreted crust\|mantle belt or directly originated from asthenosphere superface by partial melting of pyrolite.Through the deeply study of the Cenozoic volcanic rocks, the effective petrological constraints on the deep\|internal geology process can be obtained. And of course, it is the window for discussion the orogeny/uplift machinism of the Qinghai—Tibet plateau.1\ Brief regional geology\;The Yumen Cenozoic volcanic rock lithodistrict belongs to the north margin of Qinghai—Tibet plateau. This lithodistrict mainly consists of Hongliuxia and Hanxia volcanic rock bodies. The Hongliuxia Pleistocene epoch volcano neck is located to the northwest of Yumen City about 40km away, consisted of tephrite and trachybasalt. The boundary line between the volcano neck and the country rocks well defined and the contact plane is almost erect. The drag structure and wrinkle have been identified in the country rocks, which were due to the upthrusting of the magma. About 100 meters away to the south of the volcano neck, there is a basaltic flowage which covers on the Cretaceous—Tertiary shale and argillaceous sandstone.The Hanxia Cenozoic volcanic rock lithodistrict is located to the west of Yumen City about 15km away, which is a river valley extending into the north piedmont of Qilian Mountain. It dissected the Cretaceous—Tertiarystratigraphic sequence. The Cenozoic volcanic rock distributed in the Hanxia river valley is a lava flowage and NWW\|trending as a long lava dome.The Hoh Xil Cenozoic volcanic rock lithodistrict is located in the north part of Qinghai—Tibet plateau. The Cenozoic intensely intracontinental volcanism in this region had formed a number of lava sheets and subvolcanic rock bodies which were in different size and now present as lava platforms with about an elevation of 5000 meters. Affected by the preexisting NWW\|trending structure zones, there formed several NWW\|trending active\|volcano zones in the area during the Cenozoic era when the magma overflowed and/or intruded near to th e ground surface.
基金The project supported by the National Natural Science Foundation of China
文摘The grey gneisses are composed of early-stage layered TTG and late-stage diapiric tonalite in-trusions.The Dabie complex,northeastern Hubei Province,may be distinguished into supracrustal sequenceand grey gneisses.Different distribution patterns of rare earth elements in the early- and late- stage gneisses,i.e.the early-stage gneisses are enriched in LREE and remarkably depleted in HREE;and late-stage isslightly enriched in LREE and unevidently depleted in HREE.Geological evidence and characteristics of el-ement ratio diagrams suggest that the TTG is mainly controlled by portional partial melting and accompa-nied with fractional crystallization.The quantitative modelling of REE pattern indicates that TTG is formedfrom amphibolite transformed from basic rocks with 25%～65% of portional partial melt while thelate-stage tonalite intrusion was also accompanied with fractional crystalization of 22% biotites.
