Neoproterozoic island arc assemblage of the Arabian–Nubian Shield(ANS)in the Eastern Desert(ED)of Egypt comprises juvenile suites of metavolcanics(MV),large amounts of meta-sedimentary rocks(MS),and voluminous metaga...Neoproterozoic island arc assemblage of the Arabian–Nubian Shield(ANS)in the Eastern Desert(ED)of Egypt comprises juvenile suites of metavolcanics(MV),large amounts of meta-sedimentary rocks(MS),and voluminous metagabbros-diorites(MGD)and syn-tectonic intrusions of older granitoids(OG).We report here the updates of these four rock units in terms of classification,distribution,chemical characteristics,geodynamic evolution,metamorphism,and ages.In addition,we discuss these integrated data to elucidate a reasonable and reliable model for crustal evolution in the ANS.The main features of these rock units indicate their relation to each other and the geodynamic environment dominated by early immature oceanic island arcs to primitive continental arcs.Integrated information of the island arc metavolcanic and plutonic rocks(gabbros,diorites,tonalites,and granodiorites)furnish evidence of the genetic relationships.These include proximity and a coeval nature in the field;all protolith magmas are subalkaline in nature following calc-alkaline series with minor tholeiitic affinities;common geochemical signature of the arc rocks and subduction-related magmatism;their similar enrichment in LREEs;and similar major element compositions with mafic melts derived from metasomatized mantle wedge.The volcano-sedimentary and the OG rocks underwent multiphase deformation events whereas the MGD complexes deformed slightly.Based on the magmatic,sedimentological,and metamorphic evolutions constrained by geochronological data as well as the progressive evolutionary trend from extensional to compressional regimes,a possible gradual decrease in the subducted slab dip angle is the most infl uential in any geodynamic model for arc assemblage in the ED of Egypt.展开更多
Gangdise tectonic belt, located in the middle part of Tibet—Qinghai plateau Tethys tectonic domain, is the most representative region in Tibet—Qinghai plateau Tethyan evolution especially in Mesozoic era. It is main...Gangdise tectonic belt, located in the middle part of Tibet—Qinghai plateau Tethys tectonic domain, is the most representative region in Tibet—Qinghai plateau Tethyan evolution especially in Mesozoic era. It is mainly covered by thick Jurassic—Cretaceous system layer. During the Mesozoic to Cenozoic era, strong island\|arc types volcanism and volcanic rocks and intrusive rocks belt.. Geologists had divided the Tibet Tethyan evolution into three or four stages (Huang, Jiqing, 1987; Pan Guitang, Li Xinzheng, 1993), according to the ocean\|land conversion process of Tethyan evolution .The Tethyan evolution and the nature of Gangdise tectonic belt had been well\|studied by geologists (Huang Jiqing, 1987; Deng Wanming, 1984; Xia Daixiang, 1986; Cheng Changlun 1987; ZhouXiang 1993; Pan Guitang, 1996). Studies showed that Gangdise tectonic belt, from upper Paleozoic to Mesozoic era, had been developed alternate multiple island arc\|basin system, and characterized by many basin types and strong tectonic\|magma activity. Based on the study of Gangdise multiple island arc\|basin system, I present another version of Gangdise tectonic belt tectonic units division and evolution here.展开更多
The Huanggang intrusive complex in northern Tongbai area was formed in Early Paleozoic. It mainly consists of ultra basic, basic, intermediate and acid rocks, dominated by intermediate and basic rocks. The complex be...The Huanggang intrusive complex in northern Tongbai area was formed in Early Paleozoic. It mainly consists of ultra basic, basic, intermediate and acid rocks, dominated by intermediate and basic rocks. The complex belongs to calc alkaline series. Geochemical characteristics of major and trace elements show that the complex was derived from the fractional crystallization of co source magma. It is suggested that the complex was formed in island arc tectonic environment and was closely related to the northward subduction of the Erlangping back arc basin. Thus, the subduction of the back arc basin can induce the island arc type magmatism similar to the one formed in the setting of ocean plate subduction.展开更多
The Kuril islands constitute a volcanic island arc-trench system, stretching from eastern Hokkaido (Japan) to Kamchatka (Russia) along the northwestern Pacific subduction system, The current arc consists of severa...The Kuril islands constitute a volcanic island arc-trench system, stretching from eastern Hokkaido (Japan) to Kamchatka (Russia) along the northwestern Pacific subduction system, The current arc consists of several volcanic islands mainly with Neogene basement and capped by several, predominantly andesitic, active subduction stratovolcanoes, Kunashir Island is the southwestern-most island of the arc, just off the Hokkaido coast and represents the study area in this paper. The island is composed of a Lower Complex of mainly late Miocene to Pliocene volcanic rocks, covered by an Upper Complex of younger (basaltic) andesitic lava flows and tuffs on which currently four active volcanic edifices are built. In the Lower Complex sub-volcanic and deeper-seated intrusives of the so-called Prasolov and Dokuchaev magmatic complexes are found, More differentiated, tonalitic-granodioritic rocks were collected from these small intrusive bodies. An early Oligocene zircon LA-ICP-MS U/Pb age of 31 Ma for the Prasolov Complex was obtained, showing that the basement of Kunashir Island is older than previously thought. Thermochronometry (apatite fission-track and U-Th-Sm/He and zircon U-ThJHe analyses) further shows that the magmatic basement of the island was rapidly exhumed in the Pleistocene to present levels in a differential pattern, with He-ages ranging from 1.9 to 0.8 Ma. It is shown that the northern section of the island was hereby exhumed more intensely.展开更多
The origin of arcuate islands and deep-sea trenches has been studied for a long time and various interpretations have been proposed. In this paper, some analytical models are put forward from a geometrical viewpoint a...The origin of arcuate islands and deep-sea trenches has been studied for a long time and various interpretations have been proposed. In this paper, some analytical models are put forward from a geometrical viewpoint and then the theoretical dip angles of the underthrusting slabs of circum-Pacific island arcs are computed and compared with those of the Benioff zone. As a result, it is found that the dip angle of the underthrusting slab is one of the main factors determining the curvature of the arcuate structure. The authors consider that this result may contribute to the plate theory.展开更多
The Pertek granitoid consisting dominantly of diorite, quartz diorite, quartz monzodiorite, tonalite and lesser granite, adamellite and syenite, is considered to form the easternmost continuation of the Central Anatol...The Pertek granitoid consisting dominantly of diorite, quartz diorite, quartz monzodiorite, tonalite and lesser granite, adamellite and syenite, is considered to form the easternmost continuation of the Central Anatolian Crystalline Complex. Diorite and monzonites of this granitoid complex are cut by the granitic dykes. The Pertek granitoid, in the study area, is found in the Permo-Triassic Keban metamorphic sequence along intrusive and tectonic contacts. Along the intrusive contacts metasomatic mineralizations are common. Granitoids are, depending on the mineralogical composition, low-, middle- high-K subalkaline features. Major oxide-SiO2 variation diagrams show that fractionation (particularly plagioclase, hornblend, pyroxene and olivine fractionation) played an important role on the granitoid formation during a continuous crystallization process. Distribution of the samples from the Pertek granitoid in the tectonic setting diagrams, and their chondrite- and primordial mantle-normalized trace element patterns resemble to the of arc-type granitoids. Trace element and rare earth element compositions indicate that the magma, from which the Pertek granitoid crystallized, derived from a mantle that was enriched by the fluids derived from the subducted slab, however this magma was contaminated by the crust during its intrusion. These geochemical characteristics are also supported by the field observations. The field and geochemical characteristics of the Pertek Granitiod suggest that they are similar to the other granitoids cropping out in the central and eastern Anatolia and they form the lateral continuation of the same magmatic belt.展开更多
The Zedong Terrane forms a discontinuous belt of volcanic and volcaniclastic rocks adjacent to the Yarlung Zangbo River in south eastern Tibet. It extends from Luobusa to 20km west of Zedong. The Zedong Terrane lies w...The Zedong Terrane forms a discontinuous belt of volcanic and volcaniclastic rocks adjacent to the Yarlung Zangbo River in south eastern Tibet. It extends from Luobusa to 20km west of Zedong. The Zedong Terrane lies within the Indus—Yarlung Zangbo suture zone and may represent an intra\|oceanic island arc that once lay between the Lhasa (Asian) and Himalayan (Indian) terranes. Rare fossils within the terrane indicate active volcanism during the Early Cretaceous.Ultramafic rocks of the Dazhuqu Terrane, including harzburgite and gabbro are thrust over the southern margin of the Zedong Terrane along a steep south\|dipping thrust fault. To the west of Zedong, this fault is marked by a distinctive zone of serpentinite. East of Zedong, the northernmost rocks of the terrane are thrust onto Oligocene molasse deposits of the Luobusa Formation and Cretaceous plutonic rocks of the Gangdese batholith (Lhasa Terrane). These thrusts form part of a northward directed thrust stack \| the Renbu\|Zedong thrust system of Yin et al.., (1994, 1999).展开更多
Deep-water gravity depositional processes and evolution in arc systems have become topics of intense research focus in recent years.This study discusses the co-evolution of volcanism and deep-water gravity flow deposi...Deep-water gravity depositional processes and evolution in arc systems have become topics of intense research focus in recent years.This study discusses the co-evolution of volcanism and deep-water gravity flow deposits at the southern margin of the Junggar Basin,based on petrology,geochronology and geochemical analyses.The results show that a massive collapse of unstable sediments from the slope was triggered by volcanism,resulting in the formation of slumping gravity flows.The occurrence of volcanic beds in the slump deposits confirm that synchronous volcanism likely affected sediment instability,triggering gravity flows.The Th/Yb,Ta/Yb and Th/Ta elemental ratios,U-Pb ages of detrital zircons and paleocurrent directions indicate that the North Tianshan(NTS)island arc represents the provenance of the Qianxia Formation.Moreover,statistical data on the pyroclastic components in the gravity flow deposits reveal an intensity index of volcanism,indicating that volcanism is strongly related to gravity flow deposits,especially in terms of the type and distribution of the deposits.A model for volcanically-triggered deep-water gravity flow deposits is established,in order to provide a more in-depth understanding of the co-evolution of volcanism and gravity flow deposits within the depositional setting of the late Paleozoic NTS oceanic subduction margin in the Junggar Basin.展开更多
The Eastern Desert of Egypt suffered a protracted period of deformation triggered by cratonization of the new juvenile crust known as the Arabian Nubian Shield(ANS),which has been proposed for potential gold discoveri...The Eastern Desert of Egypt suffered a protracted period of deformation triggered by cratonization of the new juvenile crust known as the Arabian Nubian Shield(ANS),which has been proposed for potential gold discoveries associated with the corresponding tectonic event.The Fatira area,on the border of Egypt’s Northern and Central Eastern Deserts,is covered with metavolcanic rocks twisted by a dextral relocation of the Fatira Shear Zone(FSZ)relative to the Barud magmatic body.The recent study evaluated many deformed post-orogenic granitic intrusions and felsite dikes associated with promising mineralization localities,notably orogenic gold deposits.The combination of various field observations and remote sensing data,followed by the analysis of aeromagnetic enhanced maps,allowed the differentiation of distinct lithologies,structural features,and hydrothermal alterations in the study area.Additionally,the integrated results obtained from the different interpretation techniques are utilized to identify and confirm the previously supposed mineralized localities in the Fatira and Abu Zawal areas and predict other matched localities.The final ASTER,Sentinel 2 hydrothermal alteration,and orientation entropy heat maps demonstrate the association between these mineralized regions and major structures related to the FSZ late stage of deformation rather than other structures studied throughout the area of interest.展开更多
The Yidun Island Arc in the Three Rivers (Jinsha River, Lancang River, Nujiang River) region of southwestern China is one of the most important Kuroko-type volcanogenic massive sulfide deposits (VMS) in China. Intra-a...The Yidun Island Arc in the Three Rivers (Jinsha River, Lancang River, Nujiang River) region of southwestern China is one of the most important Kuroko-type volcanogenic massive sulfide deposits (VMS) in China. Intra-arc rifting of Yidun Island occurred during the Late Carnian-Norian when VMS deposits such as the Gacun Pb-Zn-Cu deposit were formed. A bivalve fauna was found in fine-grained tuffaceous slate and in mineralized tuffaceous siltstone containing very high contents of Pb (45.01-103.37 ppm) and Zn (135.78-300.03 ppm) of the upper Tumugou Formation in the Changtai-Gacun volcanic-sedimentary rift basin. Stratigraphically, the bivalve-bearing beds are equivalents of the Gacun Pb-Zn-Cu deposits. The diversity of this bivalve fauna is very low. It consists mainly of the thin-shelled, epibyssate suspension-feeding bivalves Pergamidia eumenea and Parapergamidia changtaiensis, the burrowing large, elongated, suspension-feeding Trigonodus keuperinus and Unionites? sp., and occasional specimens of the endobyssate suspension-feeding Trigonodus? sp. and the deep burrowing suspension-feeding Pleuromya markiamensis. Individuals of the first four taxa are so abundant that the specimens are sometimes concentrated in shell beds, probably indicating a gregarious habit. This bivalve fauna is associated with internal moulds of cylindrical, slightly conical tubes most likely produced by a worm-shaped organism. Composition, morphology, diversity, and high abundance of this fauna, chemical features of the surrounding sediment, and the tectonic setting all suggest that this bivalve fauna lived in a deep-water environment in or around a hydrothermal vent system.展开更多
文摘Neoproterozoic island arc assemblage of the Arabian–Nubian Shield(ANS)in the Eastern Desert(ED)of Egypt comprises juvenile suites of metavolcanics(MV),large amounts of meta-sedimentary rocks(MS),and voluminous metagabbros-diorites(MGD)and syn-tectonic intrusions of older granitoids(OG).We report here the updates of these four rock units in terms of classification,distribution,chemical characteristics,geodynamic evolution,metamorphism,and ages.In addition,we discuss these integrated data to elucidate a reasonable and reliable model for crustal evolution in the ANS.The main features of these rock units indicate their relation to each other and the geodynamic environment dominated by early immature oceanic island arcs to primitive continental arcs.Integrated information of the island arc metavolcanic and plutonic rocks(gabbros,diorites,tonalites,and granodiorites)furnish evidence of the genetic relationships.These include proximity and a coeval nature in the field;all protolith magmas are subalkaline in nature following calc-alkaline series with minor tholeiitic affinities;common geochemical signature of the arc rocks and subduction-related magmatism;their similar enrichment in LREEs;and similar major element compositions with mafic melts derived from metasomatized mantle wedge.The volcano-sedimentary and the OG rocks underwent multiphase deformation events whereas the MGD complexes deformed slightly.Based on the magmatic,sedimentological,and metamorphic evolutions constrained by geochronological data as well as the progressive evolutionary trend from extensional to compressional regimes,a possible gradual decrease in the subducted slab dip angle is the most infl uential in any geodynamic model for arc assemblage in the ED of Egypt.
文摘Gangdise tectonic belt, located in the middle part of Tibet—Qinghai plateau Tethys tectonic domain, is the most representative region in Tibet—Qinghai plateau Tethyan evolution especially in Mesozoic era. It is mainly covered by thick Jurassic—Cretaceous system layer. During the Mesozoic to Cenozoic era, strong island\|arc types volcanism and volcanic rocks and intrusive rocks belt.. Geologists had divided the Tibet Tethyan evolution into three or four stages (Huang, Jiqing, 1987; Pan Guitang, Li Xinzheng, 1993), according to the ocean\|land conversion process of Tethyan evolution .The Tethyan evolution and the nature of Gangdise tectonic belt had been well\|studied by geologists (Huang Jiqing, 1987; Deng Wanming, 1984; Xia Daixiang, 1986; Cheng Changlun 1987; ZhouXiang 1993; Pan Guitang, 1996). Studies showed that Gangdise tectonic belt, from upper Paleozoic to Mesozoic era, had been developed alternate multiple island arc\|basin system, and characterized by many basin types and strong tectonic\|magma activity. Based on the study of Gangdise multiple island arc\|basin system, I present another version of Gangdise tectonic belt tectonic units division and evolution here.
文摘The Huanggang intrusive complex in northern Tongbai area was formed in Early Paleozoic. It mainly consists of ultra basic, basic, intermediate and acid rocks, dominated by intermediate and basic rocks. The complex belongs to calc alkaline series. Geochemical characteristics of major and trace elements show that the complex was derived from the fractional crystallization of co source magma. It is suggested that the complex was formed in island arc tectonic environment and was closely related to the northward subduction of the Erlangping back arc basin. Thus, the subduction of the back arc basin can induce the island arc type magmatism similar to the one formed in the setting of ocean plate subduction.
基金supported by a start-up grant from the Faculty of Sciences,Ghent University(JDG)and the Australian Research Council(Grant No.DP150101730)
文摘The Kuril islands constitute a volcanic island arc-trench system, stretching from eastern Hokkaido (Japan) to Kamchatka (Russia) along the northwestern Pacific subduction system, The current arc consists of several volcanic islands mainly with Neogene basement and capped by several, predominantly andesitic, active subduction stratovolcanoes, Kunashir Island is the southwestern-most island of the arc, just off the Hokkaido coast and represents the study area in this paper. The island is composed of a Lower Complex of mainly late Miocene to Pliocene volcanic rocks, covered by an Upper Complex of younger (basaltic) andesitic lava flows and tuffs on which currently four active volcanic edifices are built. In the Lower Complex sub-volcanic and deeper-seated intrusives of the so-called Prasolov and Dokuchaev magmatic complexes are found, More differentiated, tonalitic-granodioritic rocks were collected from these small intrusive bodies. An early Oligocene zircon LA-ICP-MS U/Pb age of 31 Ma for the Prasolov Complex was obtained, showing that the basement of Kunashir Island is older than previously thought. Thermochronometry (apatite fission-track and U-Th-Sm/He and zircon U-ThJHe analyses) further shows that the magmatic basement of the island was rapidly exhumed in the Pleistocene to present levels in a differential pattern, with He-ages ranging from 1.9 to 0.8 Ma. It is shown that the northern section of the island was hereby exhumed more intensely.
文摘The origin of arcuate islands and deep-sea trenches has been studied for a long time and various interpretations have been proposed. In this paper, some analytical models are put forward from a geometrical viewpoint and then the theoretical dip angles of the underthrusting slabs of circum-Pacific island arcs are computed and compared with those of the Benioff zone. As a result, it is found that the dip angle of the underthrusting slab is one of the main factors determining the curvature of the arcuate structure. The authors consider that this result may contribute to the plate theory.
基金the University of Firat,Project number FUBAP-1109(Firat University Scientific Research Projects Unit).
文摘The Pertek granitoid consisting dominantly of diorite, quartz diorite, quartz monzodiorite, tonalite and lesser granite, adamellite and syenite, is considered to form the easternmost continuation of the Central Anatolian Crystalline Complex. Diorite and monzonites of this granitoid complex are cut by the granitic dykes. The Pertek granitoid, in the study area, is found in the Permo-Triassic Keban metamorphic sequence along intrusive and tectonic contacts. Along the intrusive contacts metasomatic mineralizations are common. Granitoids are, depending on the mineralogical composition, low-, middle- high-K subalkaline features. Major oxide-SiO2 variation diagrams show that fractionation (particularly plagioclase, hornblend, pyroxene and olivine fractionation) played an important role on the granitoid formation during a continuous crystallization process. Distribution of the samples from the Pertek granitoid in the tectonic setting diagrams, and their chondrite- and primordial mantle-normalized trace element patterns resemble to the of arc-type granitoids. Trace element and rare earth element compositions indicate that the magma, from which the Pertek granitoid crystallized, derived from a mantle that was enriched by the fluids derived from the subducted slab, however this magma was contaminated by the crust during its intrusion. These geochemical characteristics are also supported by the field observations. The field and geochemical characteristics of the Pertek Granitiod suggest that they are similar to the other granitoids cropping out in the central and eastern Anatolia and they form the lateral continuation of the same magmatic belt.
文摘The Zedong Terrane forms a discontinuous belt of volcanic and volcaniclastic rocks adjacent to the Yarlung Zangbo River in south eastern Tibet. It extends from Luobusa to 20km west of Zedong. The Zedong Terrane lies within the Indus—Yarlung Zangbo suture zone and may represent an intra\|oceanic island arc that once lay between the Lhasa (Asian) and Himalayan (Indian) terranes. Rare fossils within the terrane indicate active volcanism during the Early Cretaceous.Ultramafic rocks of the Dazhuqu Terrane, including harzburgite and gabbro are thrust over the southern margin of the Zedong Terrane along a steep south\|dipping thrust fault. To the west of Zedong, this fault is marked by a distinctive zone of serpentinite. East of Zedong, the northernmost rocks of the terrane are thrust onto Oligocene molasse deposits of the Luobusa Formation and Cretaceous plutonic rocks of the Gangdese batholith (Lhasa Terrane). These thrusts form part of a northward directed thrust stack \| the Renbu\|Zedong thrust system of Yin et al.., (1994, 1999).
基金jointly funded by the National Natural Science Foundation of China(Grant Nos.41972120,42172129)the State Key Laboratory of Paleobiology and Stratigraphy(Nanjing Institute of Geology and Paleontology,CAS)(Grant No.173131)+1 种基金the Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance(Grant No.2020CX050103)the China Postdoctoral Science Foundation(Grant No.2021M702720)。
文摘Deep-water gravity depositional processes and evolution in arc systems have become topics of intense research focus in recent years.This study discusses the co-evolution of volcanism and deep-water gravity flow deposits at the southern margin of the Junggar Basin,based on petrology,geochronology and geochemical analyses.The results show that a massive collapse of unstable sediments from the slope was triggered by volcanism,resulting in the formation of slumping gravity flows.The occurrence of volcanic beds in the slump deposits confirm that synchronous volcanism likely affected sediment instability,triggering gravity flows.The Th/Yb,Ta/Yb and Th/Ta elemental ratios,U-Pb ages of detrital zircons and paleocurrent directions indicate that the North Tianshan(NTS)island arc represents the provenance of the Qianxia Formation.Moreover,statistical data on the pyroclastic components in the gravity flow deposits reveal an intensity index of volcanism,indicating that volcanism is strongly related to gravity flow deposits,especially in terms of the type and distribution of the deposits.A model for volcanically-triggered deep-water gravity flow deposits is established,in order to provide a more in-depth understanding of the co-evolution of volcanism and gravity flow deposits within the depositional setting of the late Paleozoic NTS oceanic subduction margin in the Junggar Basin.
基金The Egyptian ministry for higher educationthe Stipendium Hungaricum scholarship are thanked for funding the first and third authors under the joint executive program between Hungary and Egypt。
文摘The Eastern Desert of Egypt suffered a protracted period of deformation triggered by cratonization of the new juvenile crust known as the Arabian Nubian Shield(ANS),which has been proposed for potential gold discoveries associated with the corresponding tectonic event.The Fatira area,on the border of Egypt’s Northern and Central Eastern Deserts,is covered with metavolcanic rocks twisted by a dextral relocation of the Fatira Shear Zone(FSZ)relative to the Barud magmatic body.The recent study evaluated many deformed post-orogenic granitic intrusions and felsite dikes associated with promising mineralization localities,notably orogenic gold deposits.The combination of various field observations and remote sensing data,followed by the analysis of aeromagnetic enhanced maps,allowed the differentiation of distinct lithologies,structural features,and hydrothermal alterations in the study area.Additionally,the integrated results obtained from the different interpretation techniques are utilized to identify and confirm the previously supposed mineralized localities in the Fatira and Abu Zawal areas and predict other matched localities.The final ASTER,Sentinel 2 hydrothermal alteration,and orientation entropy heat maps demonstrate the association between these mineralized regions and major structures related to the FSZ late stage of deformation rather than other structures studied throughout the area of interest.
基金supported by National Science Foundation of China (Grant Nos. 40372014, 40172011, 40472013, 40743016 and 41173058)the fund of Cross Century Talent of Ministry of Education of China, the Distinguished Young Scholar grant of Sichuan Province and China Scholarship Council
文摘The Yidun Island Arc in the Three Rivers (Jinsha River, Lancang River, Nujiang River) region of southwestern China is one of the most important Kuroko-type volcanogenic massive sulfide deposits (VMS) in China. Intra-arc rifting of Yidun Island occurred during the Late Carnian-Norian when VMS deposits such as the Gacun Pb-Zn-Cu deposit were formed. A bivalve fauna was found in fine-grained tuffaceous slate and in mineralized tuffaceous siltstone containing very high contents of Pb (45.01-103.37 ppm) and Zn (135.78-300.03 ppm) of the upper Tumugou Formation in the Changtai-Gacun volcanic-sedimentary rift basin. Stratigraphically, the bivalve-bearing beds are equivalents of the Gacun Pb-Zn-Cu deposits. The diversity of this bivalve fauna is very low. It consists mainly of the thin-shelled, epibyssate suspension-feeding bivalves Pergamidia eumenea and Parapergamidia changtaiensis, the burrowing large, elongated, suspension-feeding Trigonodus keuperinus and Unionites? sp., and occasional specimens of the endobyssate suspension-feeding Trigonodus? sp. and the deep burrowing suspension-feeding Pleuromya markiamensis. Individuals of the first four taxa are so abundant that the specimens are sometimes concentrated in shell beds, probably indicating a gregarious habit. This bivalve fauna is associated with internal moulds of cylindrical, slightly conical tubes most likely produced by a worm-shaped organism. Composition, morphology, diversity, and high abundance of this fauna, chemical features of the surrounding sediment, and the tectonic setting all suggest that this bivalve fauna lived in a deep-water environment in or around a hydrothermal vent system.