The Sanjiang Tethys orogenic belt is located in the southeast side of the Qinghai-Tibet Plateau. It has undergone the opening and closing movements in different periods of Tethys oceans, complex accretive orogeny and ...The Sanjiang Tethys orogenic belt is located in the southeast side of the Qinghai-Tibet Plateau. It has undergone the opening and closing movements in different periods of Tethys oceans, complex accretive orogeny and strong mineralization from Paleozoic to Mesozoic. Using zircon fission track(ZFT) thermochronology, this study reveals the Sanjiang Tethys has experienced multi-stage tectonic activities during the Late Triassic–Cenozoic. The 15 ZFT ages with their decomposition components obtained from Sanjiang Tethysian region range from 212 to 19 Ma, which not only shows 6 age groups of 212, 179–172, 156–133, 121–96, 84–70 and 50–19 Ma, but also constrains the age limit of the tectonothermal events. These age groups recorded the Paleo-Tethys main and branches ocean opening/closure time. The age-elevation plot indicates the Sanjiang region had differential uplifting and exhumation and fast uplifting times of ca. 133, 116 and 80 Ma, coinciding with the age groups mentioned above. These results show new geochronological evidences and viewpoints.展开更多
Sanjiang area in Southwestern China is tectonically situated at the east end of Himalaya-Tethys tectonic domain and at the conjunction of Tethyan Mountain Chain and Circum-Pacific Mountain Chain. It is one of the key ...Sanjiang area in Southwestern China is tectonically situated at the east end of Himalaya-Tethys tectonic domain and at the conjunction of Tethyan Mountain Chain and Circum-Pacific Mountain Chain. It is one of the key areas to understand the global tectonics and also one of gigantic metallogenic provinces in China and even in the world . Volcanism had occurred during the period of time from Proterozoic to Cenozoic . The most important and active periods of volcanism , however , are Carboniferous , Permian and Triassic . The pattern of spatial distribution of Sanjiang volcanic rocks and ophiolites can essentially be described as that several intra - continental micro-massif volcanic districts are respectively sandwiched between each two of four coupling ophioh'te - arc volcanic belts , which are successively from west to east : Dingqing - Nujiang belt , Lancangjiang belt , Jinshajiang belt and Ganzi-Litang belt . Four tectono - magma tic types of volcanic rocks have been rec-ognized in Sanjiang area as follows: mid -ocean- ridge/ para - mid - ocean - ridge type , arc type , collision type and intra - continent type . The petrotectonic assemblages within suture zones , such as oceanic assemblage , subduction - related assemblage , collision - related assemblage etc ., have been paid more attention to because of their significant importance in reconstruction of the history of Sanjiang Tethyan orogenic belt and plate tectonics .Couph'ng ophiolite - arc volcanic belt, para-mid - ocean - ridge volcanism and volcanic rocks, post -collision arc volcanism and volcanic rocks and tensional volcanic arc are newly defined in the present work . These new facts and concepts will be greatly beneficial to understanding the history of Sanjiang Tethyan plate tectonics and the complexity of the volcanism in orogenic belts and of the evolution of the continental lithosphere . A preliminary model of the evolution of Sanjiang Tethys under petrotectonic constraints was presented . It consists of the following four successive stages : (1)展开更多
The Muchang composite intrusion is located about 14 km southeast of the Fengwei town and south of the Baoshan-Zhenkang block.The rift-related intrusion consists of the early-stage riebeckite nordmarkite in the east an...The Muchang composite intrusion is located about 14 km southeast of the Fengwei town and south of the Baoshan-Zhenkang block.The rift-related intrusion consists of the early-stage riebeckite nordmarkite in the east and west sides and the discontinuous marginal zone,the late-stage main body of dominant riebeckite granite,and minor aegirine granite.Studies on petrological geochemistry and LA-ICP-MS zircon U-Pb dating of the late-stage riebeckite granite,origin and evolution of the Muchang alkali granite and the relationship between the granite and the associated skarn-type Luziyuan Pb-Zn deposit are discussed in this paper.The results show that the Muchang alkali granites belong to A-type granites,which are characterized by enrichment in Al_2O_3,SiO_2,total alkali and Fe, depletion in MgO and CaO contents with high FeO_T/MgO ratios.The REE concentrations are relatively high,exhibiting highly fractionated LREE patterns with significantly Eu negative anomaly. The Muchang granites are obviously enriched in lithophile elements（e.g.,Rb,K,U and Th） and high field strength elements（e.g.,Zr,Hf,Nb,Y and Ga） with high 10000×Ga/Al ratios and depleted in Sr, Ba,Ti,Cr and Ni,which are similar to those of the A-type granites and quite different from those of S-type andⅠ-type granites.The LA-ICP-MS zircon dating results of the Muchang granite gave a weighted mean age of 266.2±5.4 Ma（2σ）,suggesting that they were formed in the stage of extension at the end of post-collision at Middle Permian and the consumption of Paleo-Tethys ocean took place before 266 Ma. It is suggested that the unexposed intermediate-acid intrusive rocks in the Luziyuan ore district,which is the ＂sister＂ rocks material of the Muchang granites and related closely to Luziyuan Pb-Zn mineralization,were the product of Middle Permian.展开更多
文摘西南三江中段兰坪地区经历了复杂的碰撞造山过程,导致成矿时间长、强度大、作用多样,复合叠加成矿突出;碰撞造山时空演化格架和成矿作用已有深入探索,而叠加成矿作用及其对碰撞造山过程的响应,构造控矿样式,及金属富集机理尚需研究。本文以碰撞造山过程与成矿系统研究为基础,选取金顶和金满等矿床为重点解剖对象,以盆地卤水和热液铅锌铜银成矿作用为主线,利用锆石LA-ICP-MS U-Pb和流体包裹体测试分析手段,解析兰坪盆地构造-流体-成矿系统。利用锆石U-Pb同位素定年获得兰坪盆地西侧片麻质花岗岩和二长花岗岩的上交点年龄和加权平均年龄为1067±20Ma和206±1Ma,分别代表了基底岩石前寒武时期变质事件的年龄,以及昌宁-孟连古特提斯洋后碰撞造山事件的年龄。在此基础上,构建了兰坪盆地的前寒武盆地基底形成、中二叠世-中三叠世前陆盆地、晚三叠世裂谷盆地、侏罗纪-白垩纪坳陷盆地、古新世-早渐新世前陆盆地和晚渐新世-中新世走滑拉分盆地等复杂的转化过程。三江特提斯兰坪盆地发育3个与碰撞造山盆地有关的Pb-ZnCu-Ag-Au-Sb-Hg成矿系统:(1)中低温热液脉型Cu-Ag多金属成矿系统,以金满-连城铜钼矿床为代表。成矿铜和铅锌矿化两期叠加,集中于早始新世(56~46Ma)和渐新世-中新世(32~21Ma)。成矿流体盐度变化于0.88%~20.51%NaC leqv之间,成矿温度较低,通常在210~270℃,显示以低温高盐度的盆地卤水为主的特征,可能受到来自富CO2的变质流体影响;(2)浅成低温热液Sb-Au-Hg-As多金属成矿系统,以笔架山锑矿床为代表。成矿时间集中于中-晚始新世。成矿流体盐度<6.0%NaC leqv,成矿温度较低,通常在145~200℃,显示以大气降水为主的特征;(3)密西西比河谷型Pb-Zn多金属成矿系统,以金顶超大型铅锌矿床为代表。成矿时间集中于32~21Ma之间。成矿流体盐度变化于1.6%~18%NaC le
基金supported by the National Program on Key Basic Research Project(973 Program)(No.2015CB452606)the National Natural Science Foundation of China(Nos.41730427,41172088)
文摘The Sanjiang Tethys orogenic belt is located in the southeast side of the Qinghai-Tibet Plateau. It has undergone the opening and closing movements in different periods of Tethys oceans, complex accretive orogeny and strong mineralization from Paleozoic to Mesozoic. Using zircon fission track(ZFT) thermochronology, this study reveals the Sanjiang Tethys has experienced multi-stage tectonic activities during the Late Triassic–Cenozoic. The 15 ZFT ages with their decomposition components obtained from Sanjiang Tethysian region range from 212 to 19 Ma, which not only shows 6 age groups of 212, 179–172, 156–133, 121–96, 84–70 and 50–19 Ma, but also constrains the age limit of the tectonothermal events. These age groups recorded the Paleo-Tethys main and branches ocean opening/closure time. The age-elevation plot indicates the Sanjiang region had differential uplifting and exhumation and fast uplifting times of ca. 133, 116 and 80 Ma, coinciding with the age groups mentioned above. These results show new geochronological evidences and viewpoints.
文摘Sanjiang area in Southwestern China is tectonically situated at the east end of Himalaya-Tethys tectonic domain and at the conjunction of Tethyan Mountain Chain and Circum-Pacific Mountain Chain. It is one of the key areas to understand the global tectonics and also one of gigantic metallogenic provinces in China and even in the world . Volcanism had occurred during the period of time from Proterozoic to Cenozoic . The most important and active periods of volcanism , however , are Carboniferous , Permian and Triassic . The pattern of spatial distribution of Sanjiang volcanic rocks and ophiolites can essentially be described as that several intra - continental micro-massif volcanic districts are respectively sandwiched between each two of four coupling ophioh'te - arc volcanic belts , which are successively from west to east : Dingqing - Nujiang belt , Lancangjiang belt , Jinshajiang belt and Ganzi-Litang belt . Four tectono - magma tic types of volcanic rocks have been rec-ognized in Sanjiang area as follows: mid -ocean- ridge/ para - mid - ocean - ridge type , arc type , collision type and intra - continent type . The petrotectonic assemblages within suture zones , such as oceanic assemblage , subduction - related assemblage , collision - related assemblage etc ., have been paid more attention to because of their significant importance in reconstruction of the history of Sanjiang Tethyan orogenic belt and plate tectonics .Couph'ng ophiolite - arc volcanic belt, para-mid - ocean - ridge volcanism and volcanic rocks, post -collision arc volcanism and volcanic rocks and tensional volcanic arc are newly defined in the present work . These new facts and concepts will be greatly beneficial to understanding the history of Sanjiang Tethyan plate tectonics and the complexity of the volcanism in orogenic belts and of the evolution of the continental lithosphere . A preliminary model of the evolution of Sanjiang Tethys under petrotectonic constraints was presented . It consists of the following four successive stages : (1)
基金supported by the National"973 Project"(No.2009CB421003)the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No:KZCX2-YW-1 36-2,KZCX2-YW- 111-03)the Foundation of State Key Lab.Of Ore Deposit Geochemistry
文摘The Muchang composite intrusion is located about 14 km southeast of the Fengwei town and south of the Baoshan-Zhenkang block.The rift-related intrusion consists of the early-stage riebeckite nordmarkite in the east and west sides and the discontinuous marginal zone,the late-stage main body of dominant riebeckite granite,and minor aegirine granite.Studies on petrological geochemistry and LA-ICP-MS zircon U-Pb dating of the late-stage riebeckite granite,origin and evolution of the Muchang alkali granite and the relationship between the granite and the associated skarn-type Luziyuan Pb-Zn deposit are discussed in this paper.The results show that the Muchang alkali granites belong to A-type granites,which are characterized by enrichment in Al_2O_3,SiO_2,total alkali and Fe, depletion in MgO and CaO contents with high FeO_T/MgO ratios.The REE concentrations are relatively high,exhibiting highly fractionated LREE patterns with significantly Eu negative anomaly. The Muchang granites are obviously enriched in lithophile elements（e.g.,Rb,K,U and Th） and high field strength elements（e.g.,Zr,Hf,Nb,Y and Ga） with high 10000×Ga/Al ratios and depleted in Sr, Ba,Ti,Cr and Ni,which are similar to those of the A-type granites and quite different from those of S-type andⅠ-type granites.The LA-ICP-MS zircon dating results of the Muchang granite gave a weighted mean age of 266.2±5.4 Ma（2σ）,suggesting that they were formed in the stage of extension at the end of post-collision at Middle Permian and the consumption of Paleo-Tethys ocean took place before 266 Ma. It is suggested that the unexposed intermediate-acid intrusive rocks in the Luziyuan ore district,which is the ＂sister＂ rocks material of the Muchang granites and related closely to Luziyuan Pb-Zn mineralization,were the product of Middle Permian.
