An early Paleozoic Proto-Tethys ocean in western Yunnan has long been postulated although no robust geological evidence has been identified.Here we investigated the recently-identified Mayidui and Wanhe ophiolitic m&#...An early Paleozoic Proto-Tethys ocean in western Yunnan has long been postulated although no robust geological evidence has been identified.Here we investigated the recently-identified Mayidui and Wanhe ophiolitic mélanges in SW Yunnan,which occurs in a N-S trending belt east of the late Paleozoic Changning-Menglian suture zone.The ophiolites consist mainly of meta-basalts(amphibole schists),meta-(cumulate)gabbros and gabbroic diorites,and meta-chert-shale,representing ancient oceanic crust and pelagic and hemipelagic sediments,respectively.Six samples of gabbros and gabbroic diorites from 3 profiles(Mayidui,Kongjiao and Yinchanghe)yielded zircon U-Pb ages between 462±6 Ma and 447±9 Ma,constraining the formation of the Mayidui and Wanhe ophiolites to Middle Ordovician.Gabbros from the Mayidui and Kongjiao profiles share similar geochemical characteristics with affinities to tholeiitic series,and are characterized by depleted to slightly enriched LREEs relative to HREEs with(La/Sm)N=0.69-1.87,(La/Yb)N=0.66-4.72.These,along with their predominantly positive wholerock eNd(t)and zircon eHf(t)values,indicate a MORB-like magma source.By contrast,the meta-mafic rocks from the Yinchanghe profile show significantly enriched LREEs((La/Sm)N=0.97-3.33,(La/Yb)N=1.19-14.93),as well as positive whole-rock eNd(t)and positive to negative zircon eHf(t)values,indicating an E-MORB-type mantle source.These geochemical features are consistent with an intra-oceanic setting for the formation of the Mayidui-Wanhe ophiolites.Our data,integrated with available geological evidence,provide robust constraints on the timing and nature of the Mayidui-Wanhe ophiolitic mélange,and suggest that the ophiolites represent remnants of the Proto-Tethys Ocean,which opened through separation of the Indochina and Simao blocks from the northern margin of Gondwana before the Early Cambrian,and evolved through to the Silurian.展开更多
In this study,we investigated Early Paleozoic magmatic rocks of the Manlai Formation exposed along the eastern margin of the Lancang terrane to better understand the tectonic history of the Proto-Tethys.We present pet...In this study,we investigated Early Paleozoic magmatic rocks of the Manlai Formation exposed along the eastern margin of the Lancang terrane to better understand the tectonic history of the Proto-Tethys.We present petrological,geochemical and whole-rock Sr-Nd and zircon Hf isotopic data for basalts and gabbros sampled from the Qianmai mélange.Zircon grains from six basaltic and gabbroic samples yielded U-Pb ages of 495-482 Ma.These rocks are characterized by tholeiitic and Nbenriched compositions,with Nb/La ratios in the range of 0.38-1.38,similar to the typical Nb-enriched basalts.All the mafic rocks show slightly negative to positiveε_(Nd)(t)(-1.67 to+4.32)and zirconε_(Hf)(t)values(-7.3 to+3.8).Elemental and isotopic data suggest that the Qianmai Nb-enriched mafic rocks were mainly derived from the mixing of an OIB-like source with a subduction-modified mantle wedge source.Together with magmatic and sedimentary records of similar ages in the Lancang terrane and the Baoshan Block,our results reveal Early Paleozoic magmatic and sedimentary sequences along an active margin of the Proto-Tethys.Taking into account the recently identified Early Paleozoic ophiolitic mélange in the Yunxian-Menghai belt,we consider the Qianmai magmatic rocks to represent the products of early-stage subduction-related magmatism within a primitive island arc or fore-arc setting associated with the southward subduction of the Proto-Tethys.We infer that prolonged south-dipping subduction on the northern margin of Gondwana persisted from the Cambrian to the Late Ordovician.展开更多
1 Introduction Sanjiang tectonic-magma belt is one of the most potential resources’metallogenic belts in China.Cenozoic alkali-rich porphyry-type gold polymetallic mineralization system is a significant characteristi...1 Introduction Sanjiang tectonic-magma belt is one of the most potential resources’metallogenic belts in China.Cenozoic alkali-rich porphyry-type gold polymetallic mineralization system is a significant characteristic of thisbelt.Chenghai-Binchuan tectonic belt,located in the western margin of the Yangtze block,is an important part展开更多
Objective The post-ore modification and preservation of porphyry copper deposits is controlled and influenced by various geological processes, and the regional uplift and denudation is the most important factors. Thi...Objective The post-ore modification and preservation of porphyry copper deposits is controlled and influenced by various geological processes, and the regional uplift and denudation is the most important factors. This study used biotite mineral geobarometer and Apatite Fission Track （AFT） to restore the uplift evolution of the granitic porphyries in the Geza arc and to obtain quantitative data of rock erosion degree and denudation rate.展开更多
The Prototethyan Ocean has been suggested as an Early Paleozoic Ocean developed at the Gondwana northern margin. However, its spatial pattern, subduction style and closure time in SW Yunnan and SE Asia still remain un...The Prototethyan Ocean has been suggested as an Early Paleozoic Ocean developed at the Gondwana northern margin. However, its spatial pattern, subduction style and closure time in SW Yunnan and SE Asia still remain unknown. The Prototethyan evolution in SW Yunnan and SE Asia and its internal connection with the South China Kwangsian(Ordo-Silurian)intracontinental orogenesis are also poorly constrained. By summarizing and analyzing the Early Paleozoic geological records in the Sibumasu and Indochina blocks, the eastern South China and SW Japan, this paper proposes the existence of a giant OrdoSilurian igneous belt along the Gondwana northern margin. A preliminary limitation has been obtained regarding the source nature and migration pattern of the igneous belt. Our data allow us to propose a model of the Early Paleozoic Andean-type active continental margin along the East Gondwana northern margin. This is the foundation to determine the southward subduction of the southern branch of the eastern Prototethyan Ocean underneath the Sibumasu and Indochina blocks along the YunxianMenghai(SW Yunnan)-Thailand Peninsula and the Tam Ky-Phouc Son suture in Central Vietnam, respectively, and the eastward linkage with the Early Paleozoic Osaka subduction zone in SW Japan across the peripheral Sanya area. These data synthetically indicate an easterly-diachronous and propagating Andean-type Cambrian(Furongian)-Silurian(Llandovery) orogenesis along the Gondwana northern margin from Nepal, NW India, South Tibet, Qiangtang to Central Vietnam across South Indochina and Sibumasu. This paper reconstructs the Early Paleozoic locations of the Sibumasu and Indochina fragments, as well as SW Japan and South China continent in the Gondwana northern margin, and proposes the far-field effect on the South China Kwangsian intra-continental orogenesis from the subduction of the Early Paleozoic Prototethyan southern branch.展开更多
The Tethys orogenic belt in SW Yunnan constitutes a critical part of the expansive Tethys-Himalayan tectonic domain.The abundant,well-preserved geologic records make it an ideal area for studying the tectonic evolutio...The Tethys orogenic belt in SW Yunnan constitutes a critical part of the expansive Tethys-Himalayan tectonic domain.The abundant,well-preserved geologic records make it an ideal area for studying the tectonic evolution of Proto-and Paleo-Tethys.In this paper,we focus on several major tectonic units in SW Yunnan and reconstruct the Tethyan evolution from the early Paleozoic to the early Mesozoic,based on stratigraphic,sedimentologic,and magmatic evidences.The recently discovered early Paleozoic Yunxian-Menghai ophiolitic belt in the Lincang Terrane situated east of the Changning-Menglian Belt represents the suture zone of the Proto-Tethys.The oceanic basin of Proto-Tehtys opened in the latest Neoproterozoic and subsequently began subducting in the late Miaolingian of the Cambrian(about 505 Ma).From the late Late Ordovician to the ealiest Silurian(about 450–442 Ma),the Proto-Tethys basin gradually closed resulting in the collision of the continental plates on both sides of the Proto-Tethyan ocean.The main collision stage occurred in the early Silurian(about 442–430 Ma)and the postcollision stage lasted from the mid-Silurian to the early Carboniferous(430–355 Ma).The earliest record of Paleo-Tethyan oceanic crust was generated in the late Devonian,and the ocean was then subducted in an eastward direction in the middle Late Carboniferous(about 310 Ma).The initial collision stage in the Paleo-Tethys took place at the end of the Permian(about 253Ma),and the main stage of the collision persisted into the early Ladinian(about 253–238 Ma).This was followed by postcollision extension from the late Ladinian to the early Jurassic(ca.238–196 Ma).We suggest that the opening of Paleo-Tethyan Ocean in SW Yunnan was a result of the extensional rift basin of the Proto-Tethys.Additionally,the activity of the Manxin mantle plume was likely a crucial factor in the rapid expansion of the Paleo-Tethyan Ocean.展开更多
文摘An early Paleozoic Proto-Tethys ocean in western Yunnan has long been postulated although no robust geological evidence has been identified.Here we investigated the recently-identified Mayidui and Wanhe ophiolitic mélanges in SW Yunnan,which occurs in a N-S trending belt east of the late Paleozoic Changning-Menglian suture zone.The ophiolites consist mainly of meta-basalts(amphibole schists),meta-(cumulate)gabbros and gabbroic diorites,and meta-chert-shale,representing ancient oceanic crust and pelagic and hemipelagic sediments,respectively.Six samples of gabbros and gabbroic diorites from 3 profiles(Mayidui,Kongjiao and Yinchanghe)yielded zircon U-Pb ages between 462±6 Ma and 447±9 Ma,constraining the formation of the Mayidui and Wanhe ophiolites to Middle Ordovician.Gabbros from the Mayidui and Kongjiao profiles share similar geochemical characteristics with affinities to tholeiitic series,and are characterized by depleted to slightly enriched LREEs relative to HREEs with(La/Sm)N=0.69-1.87,(La/Yb)N=0.66-4.72.These,along with their predominantly positive wholerock eNd(t)and zircon eHf(t)values,indicate a MORB-like magma source.By contrast,the meta-mafic rocks from the Yinchanghe profile show significantly enriched LREEs((La/Sm)N=0.97-3.33,(La/Yb)N=1.19-14.93),as well as positive whole-rock eNd(t)and positive to negative zircon eHf(t)values,indicating an E-MORB-type mantle source.These geochemical features are consistent with an intra-oceanic setting for the formation of the Mayidui-Wanhe ophiolites.Our data,integrated with available geological evidence,provide robust constraints on the timing and nature of the Mayidui-Wanhe ophiolitic mélange,and suggest that the ophiolites represent remnants of the Proto-Tethys Ocean,which opened through separation of the Indochina and Simao blocks from the northern margin of Gondwana before the Early Cambrian,and evolved through to the Silurian.
基金supported by projects from the“Xingdian Talent”Youth Talent Program in Yunnan Province(No.XDYCQNRC-2022-0041)the National Natural Science Foundation of China(Nos.42162020,41873062,92055314)。
文摘In this study,we investigated Early Paleozoic magmatic rocks of the Manlai Formation exposed along the eastern margin of the Lancang terrane to better understand the tectonic history of the Proto-Tethys.We present petrological,geochemical and whole-rock Sr-Nd and zircon Hf isotopic data for basalts and gabbros sampled from the Qianmai mélange.Zircon grains from six basaltic and gabbroic samples yielded U-Pb ages of 495-482 Ma.These rocks are characterized by tholeiitic and Nbenriched compositions,with Nb/La ratios in the range of 0.38-1.38,similar to the typical Nb-enriched basalts.All the mafic rocks show slightly negative to positiveε_(Nd)(t)(-1.67 to+4.32)and zirconε_(Hf)(t)values(-7.3 to+3.8).Elemental and isotopic data suggest that the Qianmai Nb-enriched mafic rocks were mainly derived from the mixing of an OIB-like source with a subduction-modified mantle wedge source.Together with magmatic and sedimentary records of similar ages in the Lancang terrane and the Baoshan Block,our results reveal Early Paleozoic magmatic and sedimentary sequences along an active margin of the Proto-Tethys.Taking into account the recently identified Early Paleozoic ophiolitic mélange in the Yunxian-Menghai belt,we consider the Qianmai magmatic rocks to represent the products of early-stage subduction-related magmatism within a primitive island arc or fore-arc setting associated with the southward subduction of the Proto-Tethys.We infer that prolonged south-dipping subduction on the northern margin of Gondwana persisted from the Cambrian to the Late Ordovician.
基金financially supported by the geological survey program of China Geological Survey(1212011120607)the basic research program of Yunnan Nonferrous Metals Geological Bureau(20131300001)
文摘1 Introduction Sanjiang tectonic-magma belt is one of the most potential resources’metallogenic belts in China.Cenozoic alkali-rich porphyry-type gold polymetallic mineralization system is a significant characteristic of thisbelt.Chenghai-Binchuan tectonic belt,located in the western margin of the Yangtze block,is an important part
基金financially supported by the National Natural Science Foundation of China(Grant No.41502076)the National Basic Research Program of China(973 Program)(Grant No.2015CB4526056)
文摘Objective The post-ore modification and preservation of porphyry copper deposits is controlled and influenced by various geological processes, and the regional uplift and denudation is the most important factors. This study used biotite mineral geobarometer and Apatite Fission Track （AFT） to restore the uplift evolution of the granitic porphyries in the Geza arc and to obtain quantitative data of rock erosion degree and denudation rate.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41830211 and U1701641)the Guangdong Basic and Applied Basic Research Foundation (Grant Nos. 2018B030312007 and 2019B1515120019)。
文摘The Prototethyan Ocean has been suggested as an Early Paleozoic Ocean developed at the Gondwana northern margin. However, its spatial pattern, subduction style and closure time in SW Yunnan and SE Asia still remain unknown. The Prototethyan evolution in SW Yunnan and SE Asia and its internal connection with the South China Kwangsian(Ordo-Silurian)intracontinental orogenesis are also poorly constrained. By summarizing and analyzing the Early Paleozoic geological records in the Sibumasu and Indochina blocks, the eastern South China and SW Japan, this paper proposes the existence of a giant OrdoSilurian igneous belt along the Gondwana northern margin. A preliminary limitation has been obtained regarding the source nature and migration pattern of the igneous belt. Our data allow us to propose a model of the Early Paleozoic Andean-type active continental margin along the East Gondwana northern margin. This is the foundation to determine the southward subduction of the southern branch of the eastern Prototethyan Ocean underneath the Sibumasu and Indochina blocks along the YunxianMenghai(SW Yunnan)-Thailand Peninsula and the Tam Ky-Phouc Son suture in Central Vietnam, respectively, and the eastward linkage with the Early Paleozoic Osaka subduction zone in SW Japan across the peripheral Sanya area. These data synthetically indicate an easterly-diachronous and propagating Andean-type Cambrian(Furongian)-Silurian(Llandovery) orogenesis along the Gondwana northern margin from Nepal, NW India, South Tibet, Qiangtang to Central Vietnam across South Indochina and Sibumasu. This paper reconstructs the Early Paleozoic locations of the Sibumasu and Indochina fragments, as well as SW Japan and South China continent in the Gondwana northern margin, and proposes the far-field effect on the South China Kwangsian intra-continental orogenesis from the subduction of the Early Paleozoic Prototethyan southern branch.
基金supported by the National Natural Science Foundation of China (Grant Nos.92055201,41672222,and 41873062)the China Geological Survey (Grant No.2011-03-04-02)。
文摘The Tethys orogenic belt in SW Yunnan constitutes a critical part of the expansive Tethys-Himalayan tectonic domain.The abundant,well-preserved geologic records make it an ideal area for studying the tectonic evolution of Proto-and Paleo-Tethys.In this paper,we focus on several major tectonic units in SW Yunnan and reconstruct the Tethyan evolution from the early Paleozoic to the early Mesozoic,based on stratigraphic,sedimentologic,and magmatic evidences.The recently discovered early Paleozoic Yunxian-Menghai ophiolitic belt in the Lincang Terrane situated east of the Changning-Menglian Belt represents the suture zone of the Proto-Tethys.The oceanic basin of Proto-Tehtys opened in the latest Neoproterozoic and subsequently began subducting in the late Miaolingian of the Cambrian(about 505 Ma).From the late Late Ordovician to the ealiest Silurian(about 450–442 Ma),the Proto-Tethys basin gradually closed resulting in the collision of the continental plates on both sides of the Proto-Tethyan ocean.The main collision stage occurred in the early Silurian(about 442–430 Ma)and the postcollision stage lasted from the mid-Silurian to the early Carboniferous(430–355 Ma).The earliest record of Paleo-Tethyan oceanic crust was generated in the late Devonian,and the ocean was then subducted in an eastward direction in the middle Late Carboniferous(about 310 Ma).The initial collision stage in the Paleo-Tethys took place at the end of the Permian(about 253Ma),and the main stage of the collision persisted into the early Ladinian(about 253–238 Ma).This was followed by postcollision extension from the late Ladinian to the early Jurassic(ca.238–196 Ma).We suggest that the opening of Paleo-Tethyan Ocean in SW Yunnan was a result of the extensional rift basin of the Proto-Tethys.Additionally,the activity of the Manxin mantle plume was likely a crucial factor in the rapid expansion of the Paleo-Tethyan Ocean.
