The West Junggar orogen,located in the southwestern Central Asian Orogenic Belt(CAOB),preserves an abundant record of tectonic processes associated with the evolution of the Junggar Ocean.In this study,we use detrital...The West Junggar orogen,located in the southwestern Central Asian Orogenic Belt(CAOB),preserves an abundant record of tectonic processes associated with the evolution of the Junggar Ocean.In this study,we use detrital zircon U–Pb age data from Ordovician to Carboniferous sandstones in the southern and central West Junggar domains,complemented by literature data,to better constrain the tectonic evolution of the southwestern CAOB.The Kekeshayi,Qiargaye,and Laba formations in the southern West Junggar domain were deposited during the Darriwilian-Sandbian,Katian-Aeronian,and Homerian-Emsian,respectively.Detrital zircon provenances of these formations display a marked shift from the southern West Junggar domain to the Paleo-Kazakhstan Continent(PKC).This suggests that the southern West Junggar intra-oceanic arc might have gradually accreted to the northern margin of the PKC prior to the Emsian,which has significantly contributed to the lateral growth of the PKC.The Carboniferous strata,Xibeikulasi,Baogutu,and Tailegula formations,in the central West Junggar domain represent a coherent sequence of volcaniclastic turbidites and were deposited in a progressively shrinking remnant oceanic basin during the Visean to Moscovian.They contain unimodal detrital zircon distributions and are derived from the local and coeval magmatic rocks in the central West Junggar domain.We propose that the final closure of the Junggar Ocean likely occurred in the end of the Late Carboniferous in response to regional amalgamation events in the southwestern CAOB,which marks the final assembly of the Kazakhstan Orocline.The central and southern West Junggar domains underwent individual evolution in the Paleozoic,and were recombined by the significant intra-continental reworking along the large-scale strike-slip faults.展开更多
Turkey is highly prone to landslides because of the geological and geographic location.The study area,which is located in a tectonically active region,has been significantly affected by mass movements.Flow type landsl...Turkey is highly prone to landslides because of the geological and geographic location.The study area,which is located in a tectonically active region,has been significantly affected by mass movements.Flow type landslides are frequently observed due to this location.This study aims at determining the source area and propagation of debris flows in the study area.We used the heuristic method to extract source areas of debris flow,and then used receiver operating characteristic(ROC)curve analysis to assess the performance of the method,and finally calculated the Area under curve(AUC)values being 83.64%and 80.39%for the success rate and prediction rate,respectively.We calculated potential propagation area and runout distance with Flow-R software.In conclusion,the obtained results(susceptibility map,propagation and runout distance)are very important for decisionmakers at the region located on an active fault zone,which is highly prone to natural disasters.The outputs of this study could be used in site selection studies,designing erosion prevention systems and protecting existing human-made structures.展开更多
Ophiolites represent fragments of ancient oceanic lithosphere,tectonically incorporated into continental margins during plate subduction or remained in the subduction–collisional orogenic belt.They provide
Fabrics of an Archean mélange belt in the Zanhuang Complex of the North China Craton(NCC)were intruded by mafic dikes and a granite pluton(Deng et al.,2013;Wang et al.,2013).Igneous zircons from an undefomed
The Archean North China Craton is composed of the Western Block,Eastern Block and the intervening Central Orogenic Belt.A 4-10 km wide and 85 km long tectonic mélange belt informally called the Zanhuang tectonic
In a paper in 1970,Brian Windley first recognised that early terrestrial and lunar anorthosites both have calcic plagioclase,and low TiO_(2)and high CaO and Al_(2)O_(3)contents.Despite these similarities,the geochemis...In a paper in 1970,Brian Windley first recognised that early terrestrial and lunar anorthosites both have calcic plagioclase,and low TiO_(2)and high CaO and Al_(2)O_(3)contents.Despite these similarities,the geochemistry of early terrestrial and lunar anorthosites has not been rigorously compared and contrasted.To this end,we compiled 425 analyses from 212 early terrestrial anorthosite occurrences and 306 analyses from 16 lunar anorthosite occurrences.This was supplemented by a compilation of plagioclase anorthite(An)contents and pyroxene Mg#from early terrestrial and lunar anorthosites.Early terrestrial anorthosites have lower whole-rock An contents but similar Mg#to lunar anorthosites.The CaO contents of lunar anorthosites are higher than those of early terrestrial anorthosites for a given MgO and Al_(2)O_(3)content,early terrestrial anorthosites have higher SiO_(2)contents than lunar anorthosites at a given MgO content,and lunar anorthosites have higher Eu/Eu*anomaly ratios yet broadly similar La/Yb and Nd/Sm ratios than early terrestrial anorthosites.Some early terrestrial anorthosites have less fractionated chondrite-normalised rare earth element(REE)patterns and less prominent positive Eu anomalies than lunar anorthosites.Lunar anorthosites have higher plagioclase An contents,yet a similar range of pyroxene Mg#compared to their early terrestrial counterparts.Some early terrestrial anorthosites are more fractionated than some lunar anorthosites.Our interpretations imply that most early terrestrial anorthosites crystallised from basaltic parental magmas that were generated by high-degree partial melting of sub-arc asthenosphere mantle wedge sources that were hydrated by slab-derived fluids,with the remainder being associated with mid-ocean ridge and mantle plume settings.Some of the arc-related early terrestrial anorthosites were influenced by crustal contamination.In addition,early terrestrial anorthosites originated from partial melting of the mantle at various depths with variable garnet residua,whereas lunar anorthosites formed without any significant garnet residua.Lower plagioclase CaO contents and pyroxene Mg#in early terrestrial anorthosites can be explained by higher proportions of clinopyroxene and olivine fractionation in terrestrial magma chambers than in the lunar magma ocean where orthopyroxene and olivine fractionation occurred.Low TiO_(2)contents in both terrestrial and lunar anorthosites reflect rutile and/or ilmenite fractionation.展开更多
黄陵穹窿位于华南扬子克拉通核部地区,出露有华南前南华纪最古老、面积最大的太古宙-古元古代崆岭杂岩（崆岭岩群）（高山和张本仁,1990;马大铨等,1997;Gao et al.,1999,2011;Qiu et al.,2000;Zhang et al.,2006;Zheng et al.,2006;Jiao...黄陵穹窿位于华南扬子克拉通核部地区,出露有华南前南华纪最古老、面积最大的太古宙-古元古代崆岭杂岩（崆岭岩群）（高山和张本仁,1990;马大铨等,1997;Gao et al.,1999,2011;Qiu et al.,2000;Zhang et al.,2006;Zheng et al.,2006;Jiao et al.,2009;Guo et al.,2014）,受后期新元古代黄陵花岗杂岩体侵入影响,大体以雾渡河大断裂为界分隔为南、北部两部分（也称为南、北崆岭群）,是扬子克拉通前南华纪基底最具代表性的岩石记录,一直受国内外地质学界的高度关注,展开更多
Plate tectonics describes the horizontal motion of rigid lithospheric plates away from midoceanic ridges and parallel to transforms, towards deep-sea trenches, where the oceanic lithosphere is subducted into the mantl...Plate tectonics describes the horizontal motion of rigid lithospheric plates away from midoceanic ridges and parallel to transforms, towards deep-sea trenches, where the oceanic lithosphere is subducted into the mantle. This process is the surface expression of modern-day heat loss from Earth. One of the biggest questions in Geosciences today is ＂when did plate tectonics begin on Earth＂ with a wide range of theories based on an equally diverse set of constraints from geology, geochemistry, numerical modeling, or pure speculation. In this contribution, we turn the coin over and ask ＂when was the last appearance in the geological record for which there is proof that plate tectonics did not operate on the planet as it does today＂. We apply the laws of uniformitarianism to the rock record to ask how far back in time is the geologic record consistent with presently-operating kinematics of plate motion, before which some other mechanisms of planetary heat loss may have been in operation. Some have suggested that evidence shows that there was no plate tectonics before 800 Ma ago, others sometime before 1.8–2.7 Ga, or before 2.7 Ga. Still others recognize evidence for plate tectonics as early as 3.0 Ga, 3.3–3.5 Ga, the age of the oldest rocks, or in the Hadean before 4.3 Ga. A key undiscussed question is： why is there such a diversity of opinion about the age at which plate tectonics can be shown to not have operated, and what criteria are the different research groups using to define plate tectonics, and to recognize evidence of plate tectonics in very old rocks？ Here, we present and evaluate data from the rock record, constrained by relevant geochemical-isotopic data, and conclude that the evidence shows indubitably that plate tectonics has been operating at least since the formation of the oldest rocks, albeit with some differences in processes, compositions, and products in earlier times of higher heat generation and mantle temperature, weaker oceanic lithosphere, hotter subduction zones caused by more slab-melt generation, and under different biological and atmospheric conditions.展开更多
The epidosites are interpreted to form in upflow zones at the base of ore-forming oceanic hydrothermal systems that vent as black smokers on the sea floor. This study presents new field, major and trace element, and o...The epidosites are interpreted to form in upflow zones at the base of ore-forming oceanic hydrothermal systems that vent as black smokers on the sea floor. This study presents new field, major and trace element, and oxygen isotope data for the recently discovered epidosites in the ca. 1.0 Ga Miaowan （庙湾） ophiolite located near the northern margin of the Yangtze craton. The ep-idosites occur mainly in the cores of strongly de-formed, lensoidal amphibolites. Field observations, major and trace elements and oxygen isotopes sug-gest that the epidosites were formed by metasoma-tism of ocean floor basalts, diabase dykes, and gabbros during seafloor hydrothermal alteration.展开更多
基金This study was financially supported by the China Geological Survey(Grant Nos.1212011120502,1212011220245,DD20179607,DD20160060)This research was also supported by an Opening fund of GRMR201607 from the State Key Lab of GPMR to A.PolatA.Polat also acknowledges the support by NSERC(Canada)and China University of Geosciences at Wuhan.
文摘The West Junggar orogen,located in the southwestern Central Asian Orogenic Belt(CAOB),preserves an abundant record of tectonic processes associated with the evolution of the Junggar Ocean.In this study,we use detrital zircon U–Pb age data from Ordovician to Carboniferous sandstones in the southern and central West Junggar domains,complemented by literature data,to better constrain the tectonic evolution of the southwestern CAOB.The Kekeshayi,Qiargaye,and Laba formations in the southern West Junggar domain were deposited during the Darriwilian-Sandbian,Katian-Aeronian,and Homerian-Emsian,respectively.Detrital zircon provenances of these formations display a marked shift from the southern West Junggar domain to the Paleo-Kazakhstan Continent(PKC).This suggests that the southern West Junggar intra-oceanic arc might have gradually accreted to the northern margin of the PKC prior to the Emsian,which has significantly contributed to the lateral growth of the PKC.The Carboniferous strata,Xibeikulasi,Baogutu,and Tailegula formations,in the central West Junggar domain represent a coherent sequence of volcaniclastic turbidites and were deposited in a progressively shrinking remnant oceanic basin during the Visean to Moscovian.They contain unimodal detrital zircon distributions and are derived from the local and coeval magmatic rocks in the central West Junggar domain.We propose that the final closure of the Junggar Ocean likely occurred in the end of the Late Carboniferous in response to regional amalgamation events in the southwestern CAOB,which marks the final assembly of the Kazakhstan Orocline.The central and southern West Junggar domains underwent individual evolution in the Paleozoic,and were recombined by the significant intra-continental reworking along the large-scale strike-slip faults.
文摘Turkey is highly prone to landslides because of the geological and geographic location.The study area,which is located in a tectonically active region,has been significantly affected by mass movements.Flow type landslides are frequently observed due to this location.This study aims at determining the source area and propagation of debris flows in the study area.We used the heuristic method to extract source areas of debris flow,and then used receiver operating characteristic(ROC)curve analysis to assess the performance of the method,and finally calculated the Area under curve(AUC)values being 83.64%and 80.39%for the success rate and prediction rate,respectively.We calculated potential propagation area and runout distance with Flow-R software.In conclusion,the obtained results(susceptibility map,propagation and runout distance)are very important for decisionmakers at the region located on an active fault zone,which is highly prone to natural disasters.The outputs of this study could be used in site selection studies,designing erosion prevention systems and protecting existing human-made structures.
基金supported by the fundings (No. 41272242) from National Natural Science Foundation of China
文摘Ophiolites represent fragments of ancient oceanic lithosphere,tectonically incorporated into continental margins during plate subduction or remained in the subduction–collisional orogenic belt.They provide
文摘Fabrics of an Archean mélange belt in the Zanhuang Complex of the North China Craton(NCC)were intruded by mafic dikes and a granite pluton(Deng et al.,2013;Wang et al.,2013).Igneous zircons from an undefomed
文摘The Archean North China Craton is composed of the Western Block,Eastern Block and the intervening Central Orogenic Belt.A 4-10 km wide and 85 km long tectonic mélange belt informally called the Zanhuang tectonic
文摘In a paper in 1970,Brian Windley first recognised that early terrestrial and lunar anorthosites both have calcic plagioclase,and low TiO_(2)and high CaO and Al_(2)O_(3)contents.Despite these similarities,the geochemistry of early terrestrial and lunar anorthosites has not been rigorously compared and contrasted.To this end,we compiled 425 analyses from 212 early terrestrial anorthosite occurrences and 306 analyses from 16 lunar anorthosite occurrences.This was supplemented by a compilation of plagioclase anorthite(An)contents and pyroxene Mg#from early terrestrial and lunar anorthosites.Early terrestrial anorthosites have lower whole-rock An contents but similar Mg#to lunar anorthosites.The CaO contents of lunar anorthosites are higher than those of early terrestrial anorthosites for a given MgO and Al_(2)O_(3)content,early terrestrial anorthosites have higher SiO_(2)contents than lunar anorthosites at a given MgO content,and lunar anorthosites have higher Eu/Eu*anomaly ratios yet broadly similar La/Yb and Nd/Sm ratios than early terrestrial anorthosites.Some early terrestrial anorthosites have less fractionated chondrite-normalised rare earth element(REE)patterns and less prominent positive Eu anomalies than lunar anorthosites.Lunar anorthosites have higher plagioclase An contents,yet a similar range of pyroxene Mg#compared to their early terrestrial counterparts.Some early terrestrial anorthosites are more fractionated than some lunar anorthosites.Our interpretations imply that most early terrestrial anorthosites crystallised from basaltic parental magmas that were generated by high-degree partial melting of sub-arc asthenosphere mantle wedge sources that were hydrated by slab-derived fluids,with the remainder being associated with mid-ocean ridge and mantle plume settings.Some of the arc-related early terrestrial anorthosites were influenced by crustal contamination.In addition,early terrestrial anorthosites originated from partial melting of the mantle at various depths with variable garnet residua,whereas lunar anorthosites formed without any significant garnet residua.Lower plagioclase CaO contents and pyroxene Mg#in early terrestrial anorthosites can be explained by higher proportions of clinopyroxene and olivine fractionation in terrestrial magma chambers than in the lunar magma ocean where orthopyroxene and olivine fractionation occurred.Low TiO_(2)contents in both terrestrial and lunar anorthosites reflect rutile and/or ilmenite fractionation.
文摘黄陵穹窿位于华南扬子克拉通核部地区,出露有华南前南华纪最古老、面积最大的太古宙-古元古代崆岭杂岩（崆岭岩群）（高山和张本仁,1990;马大铨等,1997;Gao et al.,1999,2011;Qiu et al.,2000;Zhang et al.,2006;Zheng et al.,2006;Jiao et al.,2009;Guo et al.,2014）,受后期新元古代黄陵花岗杂岩体侵入影响,大体以雾渡河大断裂为界分隔为南、北部两部分（也称为南、北崆岭群）,是扬子克拉通前南华纪基底最具代表性的岩石记录,一直受国内外地质学界的高度关注,
基金supported by the National Natural Science Foundation of China (Nos.91755213,41672212,41572203)the MOST Special Fund (No.MSFGPMR02-3)+1 种基金the Opening Fund (Nos.GPMR201607,201701)the State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences (Wuhan)
文摘Plate tectonics describes the horizontal motion of rigid lithospheric plates away from midoceanic ridges and parallel to transforms, towards deep-sea trenches, where the oceanic lithosphere is subducted into the mantle. This process is the surface expression of modern-day heat loss from Earth. One of the biggest questions in Geosciences today is ＂when did plate tectonics begin on Earth＂ with a wide range of theories based on an equally diverse set of constraints from geology, geochemistry, numerical modeling, or pure speculation. In this contribution, we turn the coin over and ask ＂when was the last appearance in the geological record for which there is proof that plate tectonics did not operate on the planet as it does today＂. We apply the laws of uniformitarianism to the rock record to ask how far back in time is the geologic record consistent with presently-operating kinematics of plate motion, before which some other mechanisms of planetary heat loss may have been in operation. Some have suggested that evidence shows that there was no plate tectonics before 800 Ma ago, others sometime before 1.8–2.7 Ga, or before 2.7 Ga. Still others recognize evidence for plate tectonics as early as 3.0 Ga, 3.3–3.5 Ga, the age of the oldest rocks, or in the Hadean before 4.3 Ga. A key undiscussed question is： why is there such a diversity of opinion about the age at which plate tectonics can be shown to not have operated, and what criteria are the different research groups using to define plate tectonics, and to recognize evidence of plate tectonics in very old rocks？ Here, we present and evaluate data from the rock record, constrained by relevant geochemical-isotopic data, and conclude that the evidence shows indubitably that plate tectonics has been operating at least since the formation of the oldest rocks, albeit with some differences in processes, compositions, and products in earlier times of higher heat generation and mantle temperature, weaker oceanic lithosphere, hotter subduction zones caused by more slab-melt generation, and under different biological and atmospheric conditions.
基金supported by the China Postdoctoral Science Foundation (No. 20100471203)the Ministry of Land and Resources (No. 1212010670104)+1 种基金the National Natural Science Foundation of China (Nos. 91014002, 40821061, 41272242)Ministry of Education of China (Nos. B07039 and TGRC201024)
文摘The epidosites are interpreted to form in upflow zones at the base of ore-forming oceanic hydrothermal systems that vent as black smokers on the sea floor. This study presents new field, major and trace element, and oxygen isotope data for the recently discovered epidosites in the ca. 1.0 Ga Miaowan （庙湾） ophiolite located near the northern margin of the Yangtze craton. The ep-idosites occur mainly in the cores of strongly de-formed, lensoidal amphibolites. Field observations, major and trace elements and oxygen isotopes sug-gest that the epidosites were formed by metasoma-tism of ocean floor basalts, diabase dykes, and gabbros during seafloor hydrothermal alteration.
