The Outangdi Formation in Jiangshan, Zhejiang, is the mixing deposit of terrigenous clastics and carbonates in Weiningian of the late Carboniferous. The mixing deposits include interbeddings, which constitute a series...The Outangdi Formation in Jiangshan, Zhejiang, is the mixing deposit of terrigenous clastics and carbonates in Weiningian of the late Carboniferous. The mixing deposits include interbeddings, which constitute a series of alternated clastic and carbonate beds and mixing within the same bed which forms ＂hunji rock＂. The Outangdi Formation has the features of intercalated marine and terrestrial deposits with the progradational sequences, which are lower fine and upper coarse sedimentary granularity in the section. Hunji rock is formed in a seashore environment. It is a mixed carbonate sediment found in beaches or tideland facies with quartz sand taken from a bayou or beach by coastwise flow and circumfluence. There are two kinds of hunji sequences： （1） interbeds of sandstone and carbonate rock in seashore environments; and （2） interbeds of clastics in river facies and carbonate rock in ocean facies. It is indicated that mixing depositions belong to ＂facies mixing＂, affected mainly by regional tectonic uplift, rise of the global sea level, and the dynamics of water medium in the basin. Regional sea level periodic changes and progradational sequences probably resulted from the intense uplift of the old land called Cathaysia. The classification and name of mixed sediments are also discussed in the present study. Interbeds and alternated beds of clastic and carbonate beds are named ＂hunji sequence＂, a new genetic term. It is suggested that hunji rock means a special sediment event of mixing terrigenous clastics and carbonates instead of a name of a specific rock.展开更多
The Jiangshan-Shaoxing tectonic zone was the northeastern boundary between the Yangtze Block and the Cathaysia Block during the Neoproterozoic and was an intracontinental orogenic belt during late of the early Paleozo...The Jiangshan-Shaoxing tectonic zone was the northeastern boundary between the Yangtze Block and the Cathaysia Block during the Neoproterozoic and was an intracontinental orogenic belt during late of the early Paleozoic. In this tectonic zone, there develops a lot of mylonite underwent strong ductile deformation and schist, gneiss, and amphibolite with medium and high grade metamorphism which was formed during the late of early Paleozoic. The research of geometry and kinematic of ductile deformation in Jiangshan-Shaoxing tectonic zone is very important to reveal the tectonic process of intracontinental orogeny. This paper uses the anisotropy of magnetic susceptibility （AMS） to determine the ductile deformation geometry and kinematic of Jiangshan-Shaoxing tectonic zone combing with the field survey. In this study, 190 specimens of 19 locations and 221 specimens of 23 locations from Wangjiazhai section and Lipu-Sizhai section were analyzed. The magnetic foliation over magnetic lineation in both Wangjiazhai and Lipu-Sizhai sections together with the field observations indicated a compressional deformation pattern. 3 and 4 strong ductile deformation zones can be established in the Wangjiazhai section and the Lipu-Sizhai section, respectively. According to the magnetic fabric and petro-fabric studies, the Northeastern Jiangshan-Shaoxing tectonic zone suffered two kinds of deformation patterns during the late early Paleozoic, i.e., the thrusting deformation followed by sinistral shear deformation.展开更多
The Jiangshan gold deposit is the largest,most recently-discovered gold deposit in the Bengbu Uplift.The ore bodies are located in the structural fracture zone of the Zhuangzili Formation(Ar3),with major Pb-Zn and Au ...The Jiangshan gold deposit is the largest,most recently-discovered gold deposit in the Bengbu Uplift.The ore bodies are located in the structural fracture zone of the Zhuangzili Formation(Ar3),with major Pb-Zn and Au reserves.In this study,LA-ICP-MS zircon U-Pb analyses yielded a crystallization age of 111.5±1.8 Ma for the quartz diorite porphyry in Jiangshan.The quartz diorite porphyry has high Ba and Sr content,with low Y and Yb content,which is similar to the characteristics of adakitic rocks.They are enriched in large ion lithophile elements(LILEs,e.g.,Ba,U)and light rare ear th elements(LREEs),while depleted in high field strength elements(HFSEs,e.g.,Nb,Ti)and heavy rare earth element(HREEs).They have zirconεHf(t)values of-23.52 to-21.14(mean=-22.32).and Hf model ages of 2419.76 to 2569.39 Ma.The magma source area is the lower crust.Magma primarily came from the partial melting of the lower crust,with the addition of some mantle material.The quartz diorite porphyries are characterized by high zircon TTi-in-zircon values(608-757°C),Ce^4+/Ce^3+ratios(71.97-1387.10)and Eu/Eu*ratios(0.46-1.08),indicating high temperature and magmatic oxygen fugacities.High temperatures can provide heat to fluids and highly oxidized magmas can control the behavior and speciation of sulfides,thus controlling the behavior of Au.Finally,the ore-forming fluid is enriched and precipitated in a favorable structural space to form the Jiangshan Au deposit.展开更多
We report here geochemical data, U-Pb zircon ages, and Hf isotopes for the high-Mg diorites (HMDs), Nb-enriched basaltic porphyrys (NEBPs) and plagiogranites (PLAGs) in the Pingshui segment of the Jiangshan-Shaoxing s...We report here geochemical data, U-Pb zircon ages, and Hf isotopes for the high-Mg diorites (HMDs), Nb-enriched basaltic porphyrys (NEBPs) and plagiogranites (PLAGs) in the Pingshui segment of the Jiangshan-Shaoxing suture zone. The HMDs are characterized by high Mg# (>60), high Na and LREE contents, depletion of HREE and HFSE, and pronounced positive εNd(t) values of 7.0 to 7.7, similar to some adakitic high-Mg andesites. The NEBPs are relatively Na-rich (Na2O/K2O>6) and display high abundances of P2O5 (～1.00%), TiO2 (～3.08%) and HFSE (e.g., Nb=9.53–10.27 ppm). Their Nd isotopic compositions (εNd(t)=6.8–8.0) are comparable to those of the HMDs. The PLAGs are metaluminous (A/CNK=0.84–0.89) and sodic (Na2O/K2O>10). Their depletion in HFSE (e.g., Nb, Ta) is consistent with “SSZ-type” plagiogranite. Zircon LA-ICP-MS U-Pb dating yields an age of 932±7 Ma for the HMD, 916±6 Ma for the NEBP, and 902±5 Ma for the PLAG, respectively, indicating that they were products of early Neoproterozoic magmatism. The PLAGs exhibit relatively high zircon Hf isotopes and positive εHf(t) values of 11.0 to 16.2, consistent with their Nd isotopic data (εNd(t)=7.5–8.4). Such features are similar to those of oceanic plagiogranites in ophiolites and distinct from those of crust-derived granites. The PLAGs were most likely derived from partial melting of subducted oceanic crust in an active continental margin. Considering these results in the context of the regional geology, we suggest that a slab window in the subducting oceanic crust between the Yangtze Block and Cathaysia Block was possibly the principal cause for the unique arc magmatism in the area. The upwelling asthenosphere below the slab window may have provided significant thermodynamic conditions.展开更多
The study of anisotropy of magnetic susceptibility (AMS) of rocks from the northern part of Jiangshan-Shaoxing collisional belt demonstrates that the minimum principal AMS axes are the most concentrated one in various...The study of anisotropy of magnetic susceptibility (AMS) of rocks from the northern part of Jiangshan-Shaoxing collisional belt demonstrates that the minimum principal AMS axes are the most concentrated one in various types of rocks. The planar projection of the minimum axis shows that the main compressive stress lies on northwest 30°-60°, which trends domi-nantly in northwest-southeast of Chencai area and arc-like disperse towards both north展开更多
基金supported by the State Key Laboratory Foundation Project(No.GPMR0508) from the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences
文摘The Outangdi Formation in Jiangshan, Zhejiang, is the mixing deposit of terrigenous clastics and carbonates in Weiningian of the late Carboniferous. The mixing deposits include interbeddings, which constitute a series of alternated clastic and carbonate beds and mixing within the same bed which forms ＂hunji rock＂. The Outangdi Formation has the features of intercalated marine and terrestrial deposits with the progradational sequences, which are lower fine and upper coarse sedimentary granularity in the section. Hunji rock is formed in a seashore environment. It is a mixed carbonate sediment found in beaches or tideland facies with quartz sand taken from a bayou or beach by coastwise flow and circumfluence. There are two kinds of hunji sequences： （1） interbeds of sandstone and carbonate rock in seashore environments; and （2） interbeds of clastics in river facies and carbonate rock in ocean facies. It is indicated that mixing depositions belong to ＂facies mixing＂, affected mainly by regional tectonic uplift, rise of the global sea level, and the dynamics of water medium in the basin. Regional sea level periodic changes and progradational sequences probably resulted from the intense uplift of the old land called Cathaysia. The classification and name of mixed sediments are also discussed in the present study. Interbeds and alternated beds of clastic and carbonate beds are named ＂hunji sequence＂, a new genetic term. It is suggested that hunji rock means a special sediment event of mixing terrigenous clastics and carbonates instead of a name of a specific rock.
基金supported by the project of geological survey and evolution of Jiangshan-Shaoxing tectonic zone from Department of Land and Resources of Zhejiang Province
文摘The Jiangshan-Shaoxing tectonic zone was the northeastern boundary between the Yangtze Block and the Cathaysia Block during the Neoproterozoic and was an intracontinental orogenic belt during late of the early Paleozoic. In this tectonic zone, there develops a lot of mylonite underwent strong ductile deformation and schist, gneiss, and amphibolite with medium and high grade metamorphism which was formed during the late of early Paleozoic. The research of geometry and kinematic of ductile deformation in Jiangshan-Shaoxing tectonic zone is very important to reveal the tectonic process of intracontinental orogeny. This paper uses the anisotropy of magnetic susceptibility （AMS） to determine the ductile deformation geometry and kinematic of Jiangshan-Shaoxing tectonic zone combing with the field survey. In this study, 190 specimens of 19 locations and 221 specimens of 23 locations from Wangjiazhai section and Lipu-Sizhai section were analyzed. The magnetic foliation over magnetic lineation in both Wangjiazhai and Lipu-Sizhai sections together with the field observations indicated a compressional deformation pattern. 3 and 4 strong ductile deformation zones can be established in the Wangjiazhai section and the Lipu-Sizhai section, respectively. According to the magnetic fabric and petro-fabric studies, the Northeastern Jiangshan-Shaoxing tectonic zone suffered two kinds of deformation patterns during the late early Paleozoic, i.e., the thrusting deformation followed by sinistral shear deformation.
基金grant-funded by the National Key R&D Program of China(2016YFC0600404)the Key R&D Program of Anhui Province(201904a07020077)the Natural Science Foundation of China(41673040)。
文摘The Jiangshan gold deposit is the largest,most recently-discovered gold deposit in the Bengbu Uplift.The ore bodies are located in the structural fracture zone of the Zhuangzili Formation(Ar3),with major Pb-Zn and Au reserves.In this study,LA-ICP-MS zircon U-Pb analyses yielded a crystallization age of 111.5±1.8 Ma for the quartz diorite porphyry in Jiangshan.The quartz diorite porphyry has high Ba and Sr content,with low Y and Yb content,which is similar to the characteristics of adakitic rocks.They are enriched in large ion lithophile elements(LILEs,e.g.,Ba,U)and light rare ear th elements(LREEs),while depleted in high field strength elements(HFSEs,e.g.,Nb,Ti)and heavy rare earth element(HREEs).They have zirconεHf(t)values of-23.52 to-21.14(mean=-22.32).and Hf model ages of 2419.76 to 2569.39 Ma.The magma source area is the lower crust.Magma primarily came from the partial melting of the lower crust,with the addition of some mantle material.The quartz diorite porphyries are characterized by high zircon TTi-in-zircon values(608-757°C),Ce^4+/Ce^3+ratios(71.97-1387.10)and Eu/Eu*ratios(0.46-1.08),indicating high temperature and magmatic oxygen fugacities.High temperatures can provide heat to fluids and highly oxidized magmas can control the behavior and speciation of sulfides,thus controlling the behavior of Au.Finally,the ore-forming fluid is enriched and precipitated in a favorable structural space to form the Jiangshan Au deposit.
基金Supported by China Geological Survey (Grant No. 1212010610611) the Ministry of Land and Resources (Grant No. 200811015)
文摘We report here geochemical data, U-Pb zircon ages, and Hf isotopes for the high-Mg diorites (HMDs), Nb-enriched basaltic porphyrys (NEBPs) and plagiogranites (PLAGs) in the Pingshui segment of the Jiangshan-Shaoxing suture zone. The HMDs are characterized by high Mg# (>60), high Na and LREE contents, depletion of HREE and HFSE, and pronounced positive εNd(t) values of 7.0 to 7.7, similar to some adakitic high-Mg andesites. The NEBPs are relatively Na-rich (Na2O/K2O>6) and display high abundances of P2O5 (～1.00%), TiO2 (～3.08%) and HFSE (e.g., Nb=9.53–10.27 ppm). Their Nd isotopic compositions (εNd(t)=6.8–8.0) are comparable to those of the HMDs. The PLAGs are metaluminous (A/CNK=0.84–0.89) and sodic (Na2O/K2O>10). Their depletion in HFSE (e.g., Nb, Ta) is consistent with “SSZ-type” plagiogranite. Zircon LA-ICP-MS U-Pb dating yields an age of 932±7 Ma for the HMD, 916±6 Ma for the NEBP, and 902±5 Ma for the PLAG, respectively, indicating that they were products of early Neoproterozoic magmatism. The PLAGs exhibit relatively high zircon Hf isotopes and positive εHf(t) values of 11.0 to 16.2, consistent with their Nd isotopic data (εNd(t)=7.5–8.4). Such features are similar to those of oceanic plagiogranites in ophiolites and distinct from those of crust-derived granites. The PLAGs were most likely derived from partial melting of subducted oceanic crust in an active continental margin. Considering these results in the context of the regional geology, we suggest that a slab window in the subducting oceanic crust between the Yangtze Block and Cathaysia Block was possibly the principal cause for the unique arc magmatism in the area. The upwelling asthenosphere below the slab window may have provided significant thermodynamic conditions.
文摘The study of anisotropy of magnetic susceptibility (AMS) of rocks from the northern part of Jiangshan-Shaoxing collisional belt demonstrates that the minimum principal AMS axes are the most concentrated one in various types of rocks. The planar projection of the minimum axis shows that the main compressive stress lies on northwest 30°-60°, which trends domi-nantly in northwest-southeast of Chencai area and arc-like disperse towards both north
