Objective The Lincang granitic batholith, extending over 370 km from north to south with an area of more than 10000 km2, is the major part of the Sanjiang region in western Yunnan, SW China, and is one key area to st...Objective The Lincang granitic batholith, extending over 370 km from north to south with an area of more than 10000 km2, is the major part of the Sanjiang region in western Yunnan, SW China, and is one key area to study the evolution of the Tethys. Previous studies all agreed that the Lincang batholith was formed in the Triassic, and widely considered its formation to be the result of Paleo- Tethyan orogeny （Dong et al., 2013）. However, the early Ordovician syenogranite has been discovered recently for the first tirne in the Lincang batholith, and its petrologic and geochronological results are presented here to provide evidence in support of its association with Proto-Tethyan orogeny. This new discovery has important significance lbr understanding the geodynamic history of the Lincang batholith and tectonic evolution of the Sanjiang region.展开更多
The Ladakh batholith is exposed along the 600km long and 20 to 80km wide NW—SE trending Ladakh range north of the Indus\|Tsangpo Suture Zone. It was emplaced into an unmetamorphosed thick pile of mafic and felsic vol...The Ladakh batholith is exposed along the 600km long and 20 to 80km wide NW—SE trending Ladakh range north of the Indus\|Tsangpo Suture Zone. It was emplaced into an unmetamorphosed thick pile of mafic and felsic volcanics, ultramafics and sediments of Upper Cretaceous\|Eocene age (Dras Volcanics, Khardung Volcanics). The granites from the Ladakh batholith within the Leh\|Khardung La and Sakti—Chang La sections (samples collected between altitude of 3600m and 5440m above mean sea level, Fig.1) have been estimated for pressure and temperature of crystallization employing the hornblende geobarometer of Schmidt (1992) and hornblende\|plagioclase geothermometer of Blundy and Holland (1990), with the results of pressure of (250±60)MPa and temperature of (695±22)℃. Therefore, these granites were solidified at a depth of (8 6±2)km suggesting an unroofing of this thickness in this region. The importance of this geobarometric data in conjunction with age data on the cooling and unroofing history of the Trans\|Himalayan Ladakh batholith and geodynamic implications of the India—Asia collision are discussed.展开更多
Hainan Island located at the southernmost tip of the continental crust of the South China Plate,has high terrestrial heat-flow values,widely-distributed hot springs,and rich geothermal resources.Intensified researches...Hainan Island located at the southernmost tip of the continental crust of the South China Plate,has high terrestrial heat-flow values,widely-distributed hot springs,and rich geothermal resources.Intensified researches on the origin and potentials of geothermal resources can promote Hainan Island's development into a clean energy island.To determine the geological conditions for the formation of geothermal resources in southern Hainan Island,we collected core samples of granites from the Baocheng batholith in southern Hainan Island and conducted systematic analysis in respect of petrology,geochronology,geochemistry,and petrophysical property.The results of this study are as follows.The Baocheng batholith in the southern Hainan Island has a crystallization age of 98.42±0.56 Ma,making it the product of magmatism in the early stage of the Late Cretaceous.It mainly consists of high-K calc-alkaline granites,which were intruded by intermediate-to-mafic veins.The Baocheng batholith has a high radioactive heat generation rate of 2.712-6.843μW/m^(3),with an average of 3.846μW/m^(3),a radioactive heat-flow value of 30.768 μW/m^(2)and a heat-flow contribution rate of 38.95%-43.95%.As shown by the results of their thermophysical property analysis,the granites have high thermal conductivity and can serve as highquality geothermal reservoirs.In combination with previous geological and geophysical data,the geothermal model of the Lingshui area was established in this study.The deep structure indicates the presence of high-conductivity and low-resistivity layers in the basement of the Baocheng batholith.It can be inferred thereby that asthenospheric upwelling may occur and that there exist two magma vents at depth in the batholith.Therefore,magmatic heat at depth and granites with high radioactive heat generation rate serve as the main heat sources in the Lingshui area.展开更多
There are two factors,source composition and magmatic differentiation,potentially controlling W-Sn mineralization.Which one is more important is widely debated and may need to be determined for each individual deposit...There are two factors,source composition and magmatic differentiation,potentially controlling W-Sn mineralization.Which one is more important is widely debated and may need to be determined for each individual deposit.The Xitian granite batholith located in South China is a natural laboratory for investigating the above problem.It consists essentially of two separate components,formed in the Triassic at ca.226 Ma and Jurassic at ca.152 Ma,respectively.The Triassic and Jurassic rocks are both composed of porphyritic and fine-grained phases.The latter resulted from highlydifferentiated porphyritic ones but they have similar textural characteristics and mineral assemblages,indicating that they reached a similar degree of crystal fractionation.Although both fine-grained phases are highly differentiated with elevated rare metal contents,economic W–Sn mineralization is rare in the Triassic granitoids and this can be attributed to less fertile source materials than their Jurassic counterparts,with a slightly more enriched isotopic signature and whole-rockεNd(226 Ma)of−10.4 to−9.2(2σ=0.2)compared withεNd(152 Ma)of−9.2 to−8.2(2σ=0.2)for the Jurassic rocks.The initial W-Sn enrichment was derived from the metasedimentary rocks and strongly enhanced by reworking of the continental crust,culminating in the Jurassic.展开更多
The Jiangda–Deqen–Weixi continental margin arc(DWCA) developed along the base of the Changdu–Simao Block and was formed as a result of the subduction of the Jinsha River Ocean Slab and the subsequent collision. The...The Jiangda–Deqen–Weixi continental margin arc(DWCA) developed along the base of the Changdu–Simao Block and was formed as a result of the subduction of the Jinsha River Ocean Slab and the subsequent collision. The Ludian batholith is located in the southern part of the DWCA and is the largest batholith in northwest Yunnan. Granite samples from the Ludian batholith yield an early Middle Permian age of 271.0 ± 2.8 Ma. The geochemical data of the early Middle Permian granitoids show high Si2 O, low P2 O5 and MgO contents that belong to calc-alkaline series and peraluminous I-type rocks. Their εHf(t) values range from-5.01 to +0.58, indicating that they were formed by hybrid magmas related to the subduction of the Jinsha River Tethys Ocean. The monzonite and monzogranite samples yield Late Permian ages of 250.6 ± 1.8 Ma and 252.1 ± 1.3 Ma, respectively. The Late Permian granitoids are high-K calc alkaline and shoshonite series metaluminous I-type rocks. Their εHf(t) values range from-4.12 to-1.68 and from-7.88 to-6.64, respectively. The mixing of crustal and mantle melts formed the parental magma of the Late Permian granitoids. This study, combined with previous work, demonstrates the process from subduction to collision of the Jinsha River Paleo-Tethys Ocean.展开更多
The East Kunlun Orogenic Belt(EKOB)in northeast margin of the Qinghai-Tibetan Plateau is an important part of the Central Orogenic System(COS).During the long-time geological evolution,complicated tectono
The Baingoin batholith is one of the largest granitic plutons in the North Lhasa terrane.Its petrogenesis and tectonic setting have been studied for decades,but remain controversial.Here we report data on geochronolog...The Baingoin batholith is one of the largest granitic plutons in the North Lhasa terrane.Its petrogenesis and tectonic setting have been studied for decades,but remain controversial.Here we report data on geochronology,geochemistry and isotopes of Early Cretaceous granitoids within the Baingoin batholith,which provide more evidence to uncover its petrogenesis and regional geodynamic processes.The Early Cretaceous magmatism yields ages of 134.4–132.0 Ma and can be divided into I-type,S-type and highly fractionated granites.The I-and S-type granites exhibit medium SiO2,high K_(2)O/Na_(2)O with negativeεNd(t)andεHf(t)values,whereas,the albite granites have very high SiO_(2)(79.04%–80.40%),very low K_(2)O/N_(2)O,negativeεNd(t)and a large variation inεHf(t).Our new data indicate that these granitoids are derived from unbalanced melting in a heterogeneous source area.The granodiorites involved had a hybrid origin from partial melting of basalt-derived and Al-rich rocks in the crust,the porphyritic monzogranites being derived from partial melting of pelitic rocks.The albite granites crystallized from residual melt separated from K-rich magma within the‘mush’process and underwent fractionation of K-feldspar.We believe that the Early Cretaceous magmatism formed in an extensional setting produced by the initial and continuous rollback of a northward-subducting slab of the NTO.展开更多
The Changning Menglian belt is an important area of research on the evolution of the Paleo Tethys ocean structure,the belt can be solved such as the Changning Menglianbeltposition;sequencestratigraphy;sedimentary envi...The Changning Menglian belt is an important area of research on the evolution of the Paleo Tethys ocean structure,the belt can be solved such as the Changning Menglianbeltposition;sequencestratigraphy;sedimentary environment;nature and its tectonic evolution history and tectonic domain and Gut Tis relationship;therefore,the research on Chang Ning Menglian zone have a great significance to solve many problems of the Sanjiang fold belt in Tethys and Himalaya tectonic area.'Hot spring'is located in the west margin of the southern Changning Menglian belt,studying Yunnan Fengqing hot spring group'geological and petrology characteristics roundly and in depth,concluding the metamorphism and deformation characteristics,clarifying the metamorphism effect and its stages,understanding the association its combination with the Changning Menglian belt between,therefore it has the great significance to solve the geological evolution history in the Sanjiang area,especially the paleo Tethyan tectonic belt,as well as Gondwana and Eurasia boundaries and other major problem.Through collect and read the literature data,measurement of field section,geological investigation,research and Study on rock sheet indoor,rock composition test,electron probe testing system,summarize the geological characteristics and petrological characteristics of'hot springs group',and through the discussion of the geochemical characteristics of rocks,explore its rock assemblages,characteristics of original rock and analysis of metamorphism and deformation stages,to provide basic data for regional geological evolution.The study shows that the main lithology is biotite quartz schist,mica schist and epimetamorphic sandstone interspersed with a small amount of phyllonite,granulite,silicalite,carbonaceous slate and phyllitic cataclasite that contains some pressure breccia.The metamorphic mineral paragenetic assemblage of the representative rock is:M1 biotite(Bi)+plagioclase(Pl)+quartz(Q),and M2 muscovite(Mus)+quartz(Q).The protolith is felsic rock and sedimentary rock that belongs to argiloid.On the basis of comparison,the stratigraphic sequence of the protolith is consistent with the type section of Wenquan formation.Along with the subduction(Hercynian)-subduction(Indosinian)-orogenic(Yanshan Himalayan period)process of Changning Menglian belt,hot springs group experienced two stages of metamorphism and three stages of deformation,metamorphic temperature at400-500℃,the pressure is foucs on 0.3-0.62Gpa,and shown the retrograde metamorphism of the low greenschist facies.Geological age of hot springs formation is early Devonian(survey team of Yunnan District three units,1980),sedimentary environment is mainly shallow and semi deep sea,observed Bouma sequence in rock slice,therefore,the depositional environment may be fan or basin of sea,the sedimentary formations are mainly clastic rocksiliceous rock formation,the upper coal—contained formation.With the Changning Meng Lian ocean expansion,ocean island begin to develop,material deposition continuing,appearing volcano material,the protolith may contain volcano matter through studying the thin section.To the Late Permian,Crust of Changning Menglian ocean begin to subduct to the east of the Yangtze block,ocean basin began to close,but it still has formation here at this time,mainly shallow carbonate formation,with proceeding of subduction,in the low temperature groove(7Km deep),due to changes in temperature and pressurer,appearing metamorphism(M1)and deformation(D1)for the first time,the shear effect produced by deformation lead to some cleavage,occurring regional foliation S1,major metamorphic minerals formed in metamorphism is long flake biotite.The main metamorphic mineral assemblages are biotite(Bi)+feldspar(Pl)+quartz(Q).Subsequently,crustal uplift,depositional break,because the Changning Meng Lianyang has closed during the Indosinian period,Baoshan-Zhenkang block in the west and the Yangtze block in the east knocked each other.In the Indosinian,under the action of faults,the hot spring formation clipping and retracing,back to a position about1-2Km depth,the position is still belongs to the low temperature groove,and occurring axial cleavage in the core of the fold,namely S2.That is,the emergence of the second metamorphism(M2)and deformation(D2).The deformation is affected by the strong pressure,so the rock have dewatered,so the second metamorphic deformation process is affected by temperature(T),pressure(Ps)and fluid(C).The main metamorphic minerals in the second generation of metamorphism is Muscovite,while there have some of biotite formed in same period,find that the first phase of biotite parallel growth of rock slice,namely S1 parallel S2,and we can see incomplete metamorphism biotite,so the the Muscovite is formed by the first stage of metamorphism and metamorphic biotite.The main mineral of the second stage metamorphism is Muscovite(Mus)+quartz(Q) Then,the crust continues to rise,the sedimentary break continues.In the Jurassic Cretaceous start orogeny,namely Yanshan period intracontinental orogeny,occurred third deformation(D3),under extrusion shearing,S3 emergencing,after Yanshan intracontinental orogenic period,in Himalayan period there have large-scale nappe structure and differential uplift and faulting.So the third deformation(D3)strengthened,with weak metamorphism,sericite emergencing.展开更多
基金financially supported by the National Nature Science Foundation of China(No.41602049)China Postdoctoral Science Foundation(No.2015M582529)+1 种基金China Geological Survey(No.121201010000150007-24 and DD20160107-03)the Foundation of Sichuan Education Department(Grant:16ZB0109)
文摘Objective The Lincang granitic batholith, extending over 370 km from north to south with an area of more than 10000 km2, is the major part of the Sanjiang region in western Yunnan, SW China, and is one key area to study the evolution of the Tethys. Previous studies all agreed that the Lincang batholith was formed in the Triassic, and widely considered its formation to be the result of Paleo- Tethyan orogeny （Dong et al., 2013）. However, the early Ordovician syenogranite has been discovered recently for the first tirne in the Lincang batholith, and its petrologic and geochronological results are presented here to provide evidence in support of its association with Proto-Tethyan orogeny. This new discovery has important significance lbr understanding the geodynamic history of the Lincang batholith and tectonic evolution of the Sanjiang region.
文摘The Ladakh batholith is exposed along the 600km long and 20 to 80km wide NW—SE trending Ladakh range north of the Indus\|Tsangpo Suture Zone. It was emplaced into an unmetamorphosed thick pile of mafic and felsic volcanics, ultramafics and sediments of Upper Cretaceous\|Eocene age (Dras Volcanics, Khardung Volcanics). The granites from the Ladakh batholith within the Leh\|Khardung La and Sakti—Chang La sections (samples collected between altitude of 3600m and 5440m above mean sea level, Fig.1) have been estimated for pressure and temperature of crystallization employing the hornblende geobarometer of Schmidt (1992) and hornblende\|plagioclase geothermometer of Blundy and Holland (1990), with the results of pressure of (250±60)MPa and temperature of (695±22)℃. Therefore, these granites were solidified at a depth of (8 6±2)km suggesting an unroofing of this thickness in this region. The importance of this geobarometric data in conjunction with age data on the cooling and unroofing history of the Trans\|Himalayan Ladakh batholith and geodynamic implications of the India—Asia collision are discussed.
基金The authors would like to extend gratitude to the fund from multiple scientific research programs,including subjects entitled Analysis and Geothermal Reservoir Stimulation Methods of Deep High-temperature Geothermal Systems in East China(No.:2021YFA0716004)Evaluation and Optimal Target Selection of Deep Geothermal Resources in the Igneous Province in South China(No.:2019YFC0604903)+1 种基金the National Key Research and Development Program of China,a project entitled Deep Geological Processes and Resource Effects of Basins(No.:U20B6001)the Joint Fund Program of the National Natural Science Foundation of China and Sinopec,and a project entitled Siting and Target Evaluation of Deep Geothermal Resources in Key Areas of Southeastern China(No.:P20041-1)of the Sinopec Science and Technology Research Program.
文摘Hainan Island located at the southernmost tip of the continental crust of the South China Plate,has high terrestrial heat-flow values,widely-distributed hot springs,and rich geothermal resources.Intensified researches on the origin and potentials of geothermal resources can promote Hainan Island's development into a clean energy island.To determine the geological conditions for the formation of geothermal resources in southern Hainan Island,we collected core samples of granites from the Baocheng batholith in southern Hainan Island and conducted systematic analysis in respect of petrology,geochronology,geochemistry,and petrophysical property.The results of this study are as follows.The Baocheng batholith in the southern Hainan Island has a crystallization age of 98.42±0.56 Ma,making it the product of magmatism in the early stage of the Late Cretaceous.It mainly consists of high-K calc-alkaline granites,which were intruded by intermediate-to-mafic veins.The Baocheng batholith has a high radioactive heat generation rate of 2.712-6.843μW/m^(3),with an average of 3.846μW/m^(3),a radioactive heat-flow value of 30.768 μW/m^(2)and a heat-flow contribution rate of 38.95%-43.95%.As shown by the results of their thermophysical property analysis,the granites have high thermal conductivity and can serve as highquality geothermal reservoirs.In combination with previous geological and geophysical data,the geothermal model of the Lingshui area was established in this study.The deep structure indicates the presence of high-conductivity and low-resistivity layers in the basement of the Baocheng batholith.It can be inferred thereby that asthenospheric upwelling may occur and that there exist two magma vents at depth in the batholith.Therefore,magmatic heat at depth and granites with high radioactive heat generation rate serve as the main heat sources in the Lingshui area.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.92162210,42172096 and 41773028).
文摘There are two factors,source composition and magmatic differentiation,potentially controlling W-Sn mineralization.Which one is more important is widely debated and may need to be determined for each individual deposit.The Xitian granite batholith located in South China is a natural laboratory for investigating the above problem.It consists essentially of two separate components,formed in the Triassic at ca.226 Ma and Jurassic at ca.152 Ma,respectively.The Triassic and Jurassic rocks are both composed of porphyritic and fine-grained phases.The latter resulted from highlydifferentiated porphyritic ones but they have similar textural characteristics and mineral assemblages,indicating that they reached a similar degree of crystal fractionation.Although both fine-grained phases are highly differentiated with elevated rare metal contents,economic W–Sn mineralization is rare in the Triassic granitoids and this can be attributed to less fertile source materials than their Jurassic counterparts,with a slightly more enriched isotopic signature and whole-rockεNd(226 Ma)of−10.4 to−9.2(2σ=0.2)compared withεNd(152 Ma)of−9.2 to−8.2(2σ=0.2)for the Jurassic rocks.The initial W-Sn enrichment was derived from the metasedimentary rocks and strongly enhanced by reworking of the continental crust,culminating in the Jurassic.
基金funded by a grant from the National Key R&D Program of China(Grant No.2018YFC0604106 and 2016YFC0600305)the Program of the China Geological Survey(Grant No.DD20190053)。
文摘The Jiangda–Deqen–Weixi continental margin arc(DWCA) developed along the base of the Changdu–Simao Block and was formed as a result of the subduction of the Jinsha River Ocean Slab and the subsequent collision. The Ludian batholith is located in the southern part of the DWCA and is the largest batholith in northwest Yunnan. Granite samples from the Ludian batholith yield an early Middle Permian age of 271.0 ± 2.8 Ma. The geochemical data of the early Middle Permian granitoids show high Si2 O, low P2 O5 and MgO contents that belong to calc-alkaline series and peraluminous I-type rocks. Their εHf(t) values range from-5.01 to +0.58, indicating that they were formed by hybrid magmas related to the subduction of the Jinsha River Tethys Ocean. The monzonite and monzogranite samples yield Late Permian ages of 250.6 ± 1.8 Ma and 252.1 ± 1.3 Ma, respectively. The Late Permian granitoids are high-K calc alkaline and shoshonite series metaluminous I-type rocks. Their εHf(t) values range from-4.12 to-1.68 and from-7.88 to-6.64, respectively. The mixing of crustal and mantle melts formed the parental magma of the Late Permian granitoids. This study, combined with previous work, demonstrates the process from subduction to collision of the Jinsha River Paleo-Tethys Ocean.
基金supported by the National Science Foundation of China (Grant No., 41472191, 41502191, 41172186, 40972136)the Special Fund for Basic Scientific Research of Central Colleages, Chang’an University (Grant Nos. 310827161002, 310827161006)+1 种基金the Commonweal Geological Surveythe Aluminum Corporation of China and the Land-Resources Department of Qinghai Province (Grant No., 200801)
文摘The East Kunlun Orogenic Belt(EKOB)in northeast margin of the Qinghai-Tibetan Plateau is an important part of the Central Orogenic System(COS).During the long-time geological evolution,complicated tectono
基金supported by grants from the National Key R&D Program of China(Nos.2022YFC2905001,2018YFC0604106 and 2018YFC0604101)the Program of the Chinese Geological Survey(Nos.DD20190167 and DD20221684)+1 种基金the Basic Research Fund of the Institute of Mineral Resources,Chinese Academy of Geological Sciences(Nos.SYSCR2019-03 and KK2017)the National Natural Science Foundation of China(No.41902097).
文摘The Baingoin batholith is one of the largest granitic plutons in the North Lhasa terrane.Its petrogenesis and tectonic setting have been studied for decades,but remain controversial.Here we report data on geochronology,geochemistry and isotopes of Early Cretaceous granitoids within the Baingoin batholith,which provide more evidence to uncover its petrogenesis and regional geodynamic processes.The Early Cretaceous magmatism yields ages of 134.4–132.0 Ma and can be divided into I-type,S-type and highly fractionated granites.The I-and S-type granites exhibit medium SiO2,high K_(2)O/Na_(2)O with negativeεNd(t)andεHf(t)values,whereas,the albite granites have very high SiO_(2)(79.04%–80.40%),very low K_(2)O/N_(2)O,negativeεNd(t)and a large variation inεHf(t).Our new data indicate that these granitoids are derived from unbalanced melting in a heterogeneous source area.The granodiorites involved had a hybrid origin from partial melting of basalt-derived and Al-rich rocks in the crust,the porphyritic monzogranites being derived from partial melting of pelitic rocks.The albite granites crystallized from residual melt separated from K-rich magma within the‘mush’process and underwent fractionation of K-feldspar.We believe that the Early Cretaceous magmatism formed in an extensional setting produced by the initial and continuous rollback of a northward-subducting slab of the NTO.
文摘The Changning Menglian belt is an important area of research on the evolution of the Paleo Tethys ocean structure,the belt can be solved such as the Changning Menglianbeltposition;sequencestratigraphy;sedimentary environment;nature and its tectonic evolution history and tectonic domain and Gut Tis relationship;therefore,the research on Chang Ning Menglian zone have a great significance to solve many problems of the Sanjiang fold belt in Tethys and Himalaya tectonic area.'Hot spring'is located in the west margin of the southern Changning Menglian belt,studying Yunnan Fengqing hot spring group'geological and petrology characteristics roundly and in depth,concluding the metamorphism and deformation characteristics,clarifying the metamorphism effect and its stages,understanding the association its combination with the Changning Menglian belt between,therefore it has the great significance to solve the geological evolution history in the Sanjiang area,especially the paleo Tethyan tectonic belt,as well as Gondwana and Eurasia boundaries and other major problem.Through collect and read the literature data,measurement of field section,geological investigation,research and Study on rock sheet indoor,rock composition test,electron probe testing system,summarize the geological characteristics and petrological characteristics of'hot springs group',and through the discussion of the geochemical characteristics of rocks,explore its rock assemblages,characteristics of original rock and analysis of metamorphism and deformation stages,to provide basic data for regional geological evolution.The study shows that the main lithology is biotite quartz schist,mica schist and epimetamorphic sandstone interspersed with a small amount of phyllonite,granulite,silicalite,carbonaceous slate and phyllitic cataclasite that contains some pressure breccia.The metamorphic mineral paragenetic assemblage of the representative rock is:M1 biotite(Bi)+plagioclase(Pl)+quartz(Q),and M2 muscovite(Mus)+quartz(Q).The protolith is felsic rock and sedimentary rock that belongs to argiloid.On the basis of comparison,the stratigraphic sequence of the protolith is consistent with the type section of Wenquan formation.Along with the subduction(Hercynian)-subduction(Indosinian)-orogenic(Yanshan Himalayan period)process of Changning Menglian belt,hot springs group experienced two stages of metamorphism and three stages of deformation,metamorphic temperature at400-500℃,the pressure is foucs on 0.3-0.62Gpa,and shown the retrograde metamorphism of the low greenschist facies.Geological age of hot springs formation is early Devonian(survey team of Yunnan District three units,1980),sedimentary environment is mainly shallow and semi deep sea,observed Bouma sequence in rock slice,therefore,the depositional environment may be fan or basin of sea,the sedimentary formations are mainly clastic rocksiliceous rock formation,the upper coal—contained formation.With the Changning Meng Lian ocean expansion,ocean island begin to develop,material deposition continuing,appearing volcano material,the protolith may contain volcano matter through studying the thin section.To the Late Permian,Crust of Changning Menglian ocean begin to subduct to the east of the Yangtze block,ocean basin began to close,but it still has formation here at this time,mainly shallow carbonate formation,with proceeding of subduction,in the low temperature groove(7Km deep),due to changes in temperature and pressurer,appearing metamorphism(M1)and deformation(D1)for the first time,the shear effect produced by deformation lead to some cleavage,occurring regional foliation S1,major metamorphic minerals formed in metamorphism is long flake biotite.The main metamorphic mineral assemblages are biotite(Bi)+feldspar(Pl)+quartz(Q).Subsequently,crustal uplift,depositional break,because the Changning Meng Lianyang has closed during the Indosinian period,Baoshan-Zhenkang block in the west and the Yangtze block in the east knocked each other.In the Indosinian,under the action of faults,the hot spring formation clipping and retracing,back to a position about1-2Km depth,the position is still belongs to the low temperature groove,and occurring axial cleavage in the core of the fold,namely S2.That is,the emergence of the second metamorphism(M2)and deformation(D2).The deformation is affected by the strong pressure,so the rock have dewatered,so the second metamorphic deformation process is affected by temperature(T),pressure(Ps)and fluid(C).The main metamorphic minerals in the second generation of metamorphism is Muscovite,while there have some of biotite formed in same period,find that the first phase of biotite parallel growth of rock slice,namely S1 parallel S2,and we can see incomplete metamorphism biotite,so the the Muscovite is formed by the first stage of metamorphism and metamorphic biotite.The main mineral of the second stage metamorphism is Muscovite(Mus)+quartz(Q) Then,the crust continues to rise,the sedimentary break continues.In the Jurassic Cretaceous start orogeny,namely Yanshan period intracontinental orogeny,occurred third deformation(D3),under extrusion shearing,S3 emergencing,after Yanshan intracontinental orogenic period,in Himalayan period there have large-scale nappe structure and differential uplift and faulting.So the third deformation(D3)strengthened,with weak metamorphism,sericite emergencing.
