Polymetallic iron ore sulphate deposits of marine volcanic rock have been developed in the Fangniugou area,Jilin Province,China,but the division of volcanic ore-bearing strata has not been specifically elucidated and ...Polymetallic iron ore sulphate deposits of marine volcanic rock have been developed in the Fangniugou area,Jilin Province,China,but the division of volcanic ore-bearing strata has not been specifically elucidated and there is disagreement about the division.The sampling and SHRIMP U-Pb zircon dating of volcanic rock for Daheishan in the Fangniugou area and the northeast slope of the Duanjiadian were described.The volcanic rock formation period and recorded the volcanic events in the Daheishan mountains were systematically researched.Two samples of high-precision U-Pb zircon dating were used to represent the volcanic rock fomation period of the Late Silurian.The measured data reflect that multiple volcanic activities occurred during the Middle Silurian,Early Silurian,Middle Ordovician and Silurian,and Late Ordovician,probably matching volcanic events in the Songnan Basin identified from zircon dating.At the same time,it is confirmed that a controversial "conglomerate of Daheishan" did in fact develop in the Late Silurian,and those sections of both the Dazigou and Xinlitun-Taoshan with graptolite had been reversed.展开更多
The volcanic rocks in western part of Jinshajiang structural belt are zonally distributed between Qiangtang and Kunlun landmasses. It is bounded on the north by Yanghu\|Hoh Xil deep fault and on the south by Bairabu C...The volcanic rocks in western part of Jinshajiang structural belt are zonally distributed between Qiangtang and Kunlun landmasses. It is bounded on the north by Yanghu\|Hoh Xil deep fault and on the south by Bairabu Co\|Ruolagangri deep fault. As component part of ophiolites in this belt, volcanic rocks consist of basalts, dorgalites, picrites, basaltic\|andesites, andesites and a few pyroclastic rocks. They mainly occur within low\|grade metamorphic and thick flysch deposits of Lower Permian and Late Triassic and are associated with gabbro, diabase, ultramafites, radiolarian silicalites and limestones. This suit of volcanics\|bearing flysch deposits had been considered as Triassic or Late Triassic stratum and also called as “Ruolagangri Group”.展开更多
Granitoids,volcanic rocks and cherts,mainly of early Paleozoic,in northern Altyn Tagh(Fig.1) are analyzed here for the purpose of the determination of the tectonic environments and their development since Early Paleoz...Granitoids,volcanic rocks and cherts,mainly of early Paleozoic,in northern Altyn Tagh(Fig.1) are analyzed here for the purpose of the determination of the tectonic environments and their development since Early Paleozoic.(1) Granitoids\ The collection of 128 main\|element petrochemical data from North Altyn Tagh area shows that most of the granitoids here are granites and granodiorites of calc\|alkaline series.They consist mainly of metaluminous and peraluminous in Shand’s index,and only one of them,which belongs to Mesozoic,is peralkaline.Most of the granitoids plot in the IAG+CAG+CCG fields in the Maniar and Piccoli’s diagrams (1989) for tectonic discrimination of granitoids.IAG (Island arc granitoids)and CAG (Continental arc granitoids) can be distinguished for Early and Late Paleozoic granitoids,and maybe some CCG (Continental collision granitoids) for Early Paleozoic.Granitoids of Mesozoic and Cenozoic inherited the characteristics of those of Paleozoic.Destructive active plate margin (pre\|plate collision)and Anatectic magmatism(syn\|orogenic,S\|type granites)are distinguished (Fig.2)for Paleozoic granitoids using de la Roche R 1\| R 2 multicationic diagram (Batchelor and Bowden,1985).Mesozoic and Cenozoic granitoids inherited the characteristics of Anatectic magmatism (syn\|orogenic)of these early ones,and post\|orogenic(A\|type)granites occurred in Mesozoic.The mechanism for magma formation is mainly partial melting.展开更多
The Cenozoic volcanic rocks in Qinghai—Tibetan plateau mainly occur in Qiangtang, Kunlun,Kokshili and eastern Tibet to the north of Bangong\|Nujiang suture. The study area locates in the centre of Qiangtang (N34°...The Cenozoic volcanic rocks in Qinghai—Tibetan plateau mainly occur in Qiangtang, Kunlun,Kokshili and eastern Tibet to the north of Bangong\|Nujiang suture. The study area locates in the centre of Qiangtang (N34°00′\|34°50′;E87°30′\|89°00′),where is nearly a blank area of geological work.Thirteen pieces of samples from Hehulin,Luanqingshan,Bandaohu and Donghu show that the K\|Ar ages of the Cenozoic volcanic rocks range from 32 6 to 44 1Ma, which are elder than the Cenozoic volcanic rocks from Kunlun,Kokshili and eastern Tibet.There are two types of occurrence for the volcanic rocks: volcanic lava and sub\|volcanic rock. The lava is dark grey, light purple or dark purple and unconformably covers up on the Jurassic,which interbeds with purplish red tertiary sandstone and pebble\|bearing sandstone and contains a small amount of phenocrysts (andesine,pyroxene,amphibole and biotite). three craters and four volcanic necks have been found in this area. The sub\|volcanic rocks expose as volcanic necks with appearance of isolated peaks,which intrude into Jurassic. The rocks,appearing grey white to light grey, have trachytic texture with the phenocrysts of plagioclase,biotite and amphibole. Besides above rocks,there are some lamprophyre dikes intruding into grey white tertiary lacustrine algal limestone in this area with its length up to 2km and width 3m. The rocks appear dark grey or dark green and contain the phenocrysts of pyroxene,orthoclase,biotite,olivine,and leucitite.展开更多
The Cenozoic volcanic rocks in the Yumen and Hoh Xil area formed in the intracontinental orogenic belt, which primary magma originated from a particular enrichment upmantle and accreted crust\|mantle belt or directly ...The Cenozoic volcanic rocks in the Yumen and Hoh Xil area formed in the intracontinental orogenic belt, which primary magma originated from a particular enrichment upmantle and accreted crust\|mantle belt or directly originated from asthenosphere superface by partial melting of pyrolite.Through the deeply study of the Cenozoic volcanic rocks, the effective petrological constraints on the deep\|internal geology process can be obtained. And of course, it is the window for discussion the orogeny/uplift machinism of the Qinghai—Tibet plateau.1\ Brief regional geology\;The Yumen Cenozoic volcanic rock lithodistrict belongs to the north margin of Qinghai—Tibet plateau. This lithodistrict mainly consists of Hongliuxia and Hanxia volcanic rock bodies. The Hongliuxia Pleistocene epoch volcano neck is located to the northwest of Yumen City about 40km away, consisted of tephrite and trachybasalt. The boundary line between the volcano neck and the country rocks well defined and the contact plane is almost erect. The drag structure and wrinkle have been identified in the country rocks, which were due to the upthrusting of the magma. About 100 meters away to the south of the volcano neck, there is a basaltic flowage which covers on the Cretaceous—Tertiary shale and argillaceous sandstone.The Hanxia Cenozoic volcanic rock lithodistrict is located to the west of Yumen City about 15km away, which is a river valley extending into the north piedmont of Qilian Mountain. It dissected the Cretaceous—Tertiarystratigraphic sequence. The Cenozoic volcanic rock distributed in the Hanxia river valley is a lava flowage and NWW\|trending as a long lava dome.The Hoh Xil Cenozoic volcanic rock lithodistrict is located in the north part of Qinghai—Tibet plateau. The Cenozoic intensely intracontinental volcanism in this region had formed a number of lava sheets and subvolcanic rock bodies which were in different size and now present as lava platforms with about an elevation of 5000 meters. Affected by the preexisting NWW\|trending structure zones, there formed several NWW\|trending active\|volcano zones in the area during the Cenozoic era when the magma overflowed and/or intruded near to th e ground surface.展开更多
Cenozoic volcanic rocks, forming a series of volcanic rocks platform or highland on different sub\|volcanic rocks belt, had distributed widely in northern Qinghai—Tibet plateau, and characterized by potassinm\|rich l...Cenozoic volcanic rocks, forming a series of volcanic rocks platform or highland on different sub\|volcanic rocks belt, had distributed widely in northern Qinghai—Tibet plateau, and characterized by potassinm\|rich lavas which main petrologic types are latidacite and latite. The petrogenesis of volcanic rocks in northern Tibetan plateau had been well\|studied, and thought they play an important role to uplift of Tibetan plateau. Based on the study of lithochemistry and isotopic age determination of the rocks in Qiangtang area, which is the most southern and earliest volcanic rocks belt of Cenozoic volcanic rocks, I contribute another view here to the early uplift of Tibetan plateau. Cenozoic volcanic rocks in Qiangtang region, thickness of the rocks are from 200 to 1000m in different area, belong to shoshonite and high\|K calc\|alkaline series, highly enrich alkaline specially enrich potassinm, large\|ion lithophytes elements (Rb,Sr,Ba,and Th), LREE and deplete high\|field strength elements (Ta,Er,Hf,and Ti). Chondrite\|normalized REE pattern of volcanic rocks show an absence of significant Eu anomaly, and indicate that the volcanic source was plagioclase\|free and probably resulted from melting in lower crust or upper mantle. Cenozoic volcanic rocks in Qiangtang region are similar petrologic and geochemical characteristics to that have been reported in more northern Hoh Xil and Kunlun area in Tibetan plateau. The age scope of volcanic rocks in Qiangtang area were from 44.1～32.6Ma, among which the age mainly were 44.1～42.5Ma, which belong to mid\|Eocene epoch to primary Oligocene epoch, and could be classified into four out pouring periods, according to the potassium\|argon age dating. The study on lithochemistry and age of the rocks in Qiangtang area suggest that Intracontinental subduction southward Qiangtang tectonic belt plays an important role to Cenozoic volcanism, and imply that the convective removal of the thicked lithosphere, which formed at the collision mountain\|building processes, are responsible for the formation of Cenozoic volcanic rocks, the earliest uplift of Tibetan plateau. and regional extension in Qiangtang area.展开更多
The age and evolutional history of the Altyn Tagh fault and its role in the formation and uplift of the Qinghai—Tibetan plateau have been focused for years. Many geologists believe that the formation of the fault is ...The age and evolutional history of the Altyn Tagh fault and its role in the formation and uplift of the Qinghai—Tibetan plateau have been focused for years. Many geologists believe that the formation of the fault is a result of the collision between India and Asia. Some people thought that it should have formed earlier than Cenozoic but have no critical evidence. Here we report a preliminary result from our recent investigation on the volcanic rocks at the north end of the Altyn Tagh fault.1 The volcanic rocks on the north end of the Altyn Tagh fault The volcanic rocks are located on the north end of the Altyn Tagh fault, northern Qinghai—Tibetan plateau. The investigated volcano occurs in the Jiuxi basin, a Cretaceous and Tertiary depositional basin. It is about 300m×100m in size and form about a 100m high cliff above the folded Cretaceous strata. It likes relic neck of a volcano rather than a kind of widely distributed lava flow commonly seen in the northern Tibet. The country rocks are Cretaceous sandstone, silt and fine\|grained conglomerate. The cliff formed most likely due to the differing erosion between the hard volcanic rocks and soft rocks.展开更多
Studied Volcanic rocks are zonally distributed between Qiangtang and Kunlun landasses, that is in the western part of Lazhulong\|Jinsajiang tectonic belt. It is bounded on the north by Yanghu\|Hohxil deep fult and on ...Studied Volcanic rocks are zonally distributed between Qiangtang and Kunlun landasses, that is in the western part of Lazhulong\|Jinsajiang tectonic belt. It is bounded on the north by Yanghu\|Hohxil deep fult and on the south by Bairabu Co\|Ruolagangri deep fault. As component part of ophiolites in this belt, volcanic rocks mainly occuring within low\|grade metamorphic and thick flysch deposits of Lower Permian and Late Triassic, are associated with gabbro, diabase, ultramafites, radiolarian silicalites and limestones, consisting of basalts, dorgalites, picrites, basaltic\|andesites, andesites and a few pyroclastic rocks. This suit of volcanics\|bearing flysch deposits had been considered as Triassic or Late Triassic stratum and also called as “Ruolagangri Group” before.The basalts in this belt are characterized by having lower SiO\-2, higher TiO\-2(1 74%～4 78%, average 2 94%) and K 2O+Na 2O(mostly 3 50%～5 00%) contents, and usually Na 2O>K 2O. The total REE abundances in basalts which vary from 115 68×10 -6 to 323 66×10 -6 are relatively high, and all of their distribution patterns show moderately or strongly LREE\|enriched. The LREE/HREE ratios range from 8 74 to 14 41, (La/Yb) N from 9 53 to 19 56, and showing faint positive or no Eu anomaly. Incompatible trace elements such as Sr, Rb, Ba, Th, Ta, Nd, P, Zr, Hf etc. are relatively concentrated, whose contents usually are several times to several tens of MORB, while Yb, Y, Sc, Cr are obviously depleted. The characteristics of Petrochemistry and rare elementary geochemistry indicate that the volcanic rocks belong to series of alkaline or subalkaline basalt and show the features of alkaline—transitional basalt under the setting of continental rift or ocean island, and also similar to that of Late Carboniferous basalts in Chabu\|Chasang area of central Qiangtang and that of Permian Emeishang basalts in southwest of China.展开更多
In these years,the Upper Jurassic andesitic volcanic reservoirs in Erlian basin,the Lower Cretaceous rhyolitic volcanic reservoirs in Songliao Basin,the Cretaceous rhyolitic,and the Paleogene basaltic and trachytic vo...In these years,the Upper Jurassic andesitic volcanic reservoirs in Erlian basin,the Lower Cretaceous rhyolitic volcanic reservoirs in Songliao Basin,the Cretaceous rhyolitic,and the Paleogene basaltic and trachytic volcanic reservoirs in Bohai Bay Basin,and the basaltic volcanic reservoirs in Subei basin were discovered.With more and more volcanic oil and gas fields being discovered and developed,the volcanic rocks demonstrate a great petroleum potential in eastern basins of China.Five volcanic facies were identified in these basins,including volcanic conduit facies,explosive facies,effusive facies。展开更多
基金Project(2009GYXQ02-06) supported by the National Oil and Gas Resources of Strategic Project Selection Survey and Evaluation Fund from Land and Natural Resources Ministry,ChinaProject(2652013099) supported by the Fundamental Research Funds of Central Universities,China
文摘Polymetallic iron ore sulphate deposits of marine volcanic rock have been developed in the Fangniugou area,Jilin Province,China,but the division of volcanic ore-bearing strata has not been specifically elucidated and there is disagreement about the division.The sampling and SHRIMP U-Pb zircon dating of volcanic rock for Daheishan in the Fangniugou area and the northeast slope of the Duanjiadian were described.The volcanic rock formation period and recorded the volcanic events in the Daheishan mountains were systematically researched.Two samples of high-precision U-Pb zircon dating were used to represent the volcanic rock fomation period of the Late Silurian.The measured data reflect that multiple volcanic activities occurred during the Middle Silurian,Early Silurian,Middle Ordovician and Silurian,and Late Ordovician,probably matching volcanic events in the Songnan Basin identified from zircon dating.At the same time,it is confirmed that a controversial "conglomerate of Daheishan" did in fact develop in the Late Silurian,and those sections of both the Dazigou and Xinlitun-Taoshan with graptolite had been reversed.
文摘The volcanic rocks in western part of Jinshajiang structural belt are zonally distributed between Qiangtang and Kunlun landmasses. It is bounded on the north by Yanghu\|Hoh Xil deep fault and on the south by Bairabu Co\|Ruolagangri deep fault. As component part of ophiolites in this belt, volcanic rocks consist of basalts, dorgalites, picrites, basaltic\|andesites, andesites and a few pyroclastic rocks. They mainly occur within low\|grade metamorphic and thick flysch deposits of Lower Permian and Late Triassic and are associated with gabbro, diabase, ultramafites, radiolarian silicalites and limestones. This suit of volcanics\|bearing flysch deposits had been considered as Triassic or Late Triassic stratum and also called as “Ruolagangri Group”.
文摘Granitoids,volcanic rocks and cherts,mainly of early Paleozoic,in northern Altyn Tagh(Fig.1) are analyzed here for the purpose of the determination of the tectonic environments and their development since Early Paleozoic.(1) Granitoids\ The collection of 128 main\|element petrochemical data from North Altyn Tagh area shows that most of the granitoids here are granites and granodiorites of calc\|alkaline series.They consist mainly of metaluminous and peraluminous in Shand’s index,and only one of them,which belongs to Mesozoic,is peralkaline.Most of the granitoids plot in the IAG+CAG+CCG fields in the Maniar and Piccoli’s diagrams (1989) for tectonic discrimination of granitoids.IAG (Island arc granitoids)and CAG (Continental arc granitoids) can be distinguished for Early and Late Paleozoic granitoids,and maybe some CCG (Continental collision granitoids) for Early Paleozoic.Granitoids of Mesozoic and Cenozoic inherited the characteristics of those of Paleozoic.Destructive active plate margin (pre\|plate collision)and Anatectic magmatism(syn\|orogenic,S\|type granites)are distinguished (Fig.2)for Paleozoic granitoids using de la Roche R 1\| R 2 multicationic diagram (Batchelor and Bowden,1985).Mesozoic and Cenozoic granitoids inherited the characteristics of Anatectic magmatism (syn\|orogenic)of these early ones,and post\|orogenic(A\|type)granites occurred in Mesozoic.The mechanism for magma formation is mainly partial melting.
文摘The Cenozoic volcanic rocks in Qinghai—Tibetan plateau mainly occur in Qiangtang, Kunlun,Kokshili and eastern Tibet to the north of Bangong\|Nujiang suture. The study area locates in the centre of Qiangtang (N34°00′\|34°50′;E87°30′\|89°00′),where is nearly a blank area of geological work.Thirteen pieces of samples from Hehulin,Luanqingshan,Bandaohu and Donghu show that the K\|Ar ages of the Cenozoic volcanic rocks range from 32 6 to 44 1Ma, which are elder than the Cenozoic volcanic rocks from Kunlun,Kokshili and eastern Tibet.There are two types of occurrence for the volcanic rocks: volcanic lava and sub\|volcanic rock. The lava is dark grey, light purple or dark purple and unconformably covers up on the Jurassic,which interbeds with purplish red tertiary sandstone and pebble\|bearing sandstone and contains a small amount of phenocrysts (andesine,pyroxene,amphibole and biotite). three craters and four volcanic necks have been found in this area. The sub\|volcanic rocks expose as volcanic necks with appearance of isolated peaks,which intrude into Jurassic. The rocks,appearing grey white to light grey, have trachytic texture with the phenocrysts of plagioclase,biotite and amphibole. Besides above rocks,there are some lamprophyre dikes intruding into grey white tertiary lacustrine algal limestone in this area with its length up to 2km and width 3m. The rocks appear dark grey or dark green and contain the phenocrysts of pyroxene,orthoclase,biotite,olivine,and leucitite.
文摘The Cenozoic volcanic rocks in the Yumen and Hoh Xil area formed in the intracontinental orogenic belt, which primary magma originated from a particular enrichment upmantle and accreted crust\|mantle belt or directly originated from asthenosphere superface by partial melting of pyrolite.Through the deeply study of the Cenozoic volcanic rocks, the effective petrological constraints on the deep\|internal geology process can be obtained. And of course, it is the window for discussion the orogeny/uplift machinism of the Qinghai—Tibet plateau.1\ Brief regional geology\;The Yumen Cenozoic volcanic rock lithodistrict belongs to the north margin of Qinghai—Tibet plateau. This lithodistrict mainly consists of Hongliuxia and Hanxia volcanic rock bodies. The Hongliuxia Pleistocene epoch volcano neck is located to the northwest of Yumen City about 40km away, consisted of tephrite and trachybasalt. The boundary line between the volcano neck and the country rocks well defined and the contact plane is almost erect. The drag structure and wrinkle have been identified in the country rocks, which were due to the upthrusting of the magma. About 100 meters away to the south of the volcano neck, there is a basaltic flowage which covers on the Cretaceous—Tertiary shale and argillaceous sandstone.The Hanxia Cenozoic volcanic rock lithodistrict is located to the west of Yumen City about 15km away, which is a river valley extending into the north piedmont of Qilian Mountain. It dissected the Cretaceous—Tertiarystratigraphic sequence. The Cenozoic volcanic rock distributed in the Hanxia river valley is a lava flowage and NWW\|trending as a long lava dome.The Hoh Xil Cenozoic volcanic rock lithodistrict is located in the north part of Qinghai—Tibet plateau. The Cenozoic intensely intracontinental volcanism in this region had formed a number of lava sheets and subvolcanic rock bodies which were in different size and now present as lava platforms with about an elevation of 5000 meters. Affected by the preexisting NWW\|trending structure zones, there formed several NWW\|trending active\|volcano zones in the area during the Cenozoic era when the magma overflowed and/or intruded near to th e ground surface.
文摘Cenozoic volcanic rocks, forming a series of volcanic rocks platform or highland on different sub\|volcanic rocks belt, had distributed widely in northern Qinghai—Tibet plateau, and characterized by potassinm\|rich lavas which main petrologic types are latidacite and latite. The petrogenesis of volcanic rocks in northern Tibetan plateau had been well\|studied, and thought they play an important role to uplift of Tibetan plateau. Based on the study of lithochemistry and isotopic age determination of the rocks in Qiangtang area, which is the most southern and earliest volcanic rocks belt of Cenozoic volcanic rocks, I contribute another view here to the early uplift of Tibetan plateau. Cenozoic volcanic rocks in Qiangtang region, thickness of the rocks are from 200 to 1000m in different area, belong to shoshonite and high\|K calc\|alkaline series, highly enrich alkaline specially enrich potassinm, large\|ion lithophytes elements (Rb,Sr,Ba,and Th), LREE and deplete high\|field strength elements (Ta,Er,Hf,and Ti). Chondrite\|normalized REE pattern of volcanic rocks show an absence of significant Eu anomaly, and indicate that the volcanic source was plagioclase\|free and probably resulted from melting in lower crust or upper mantle. Cenozoic volcanic rocks in Qiangtang region are similar petrologic and geochemical characteristics to that have been reported in more northern Hoh Xil and Kunlun area in Tibetan plateau. The age scope of volcanic rocks in Qiangtang area were from 44.1～32.6Ma, among which the age mainly were 44.1～42.5Ma, which belong to mid\|Eocene epoch to primary Oligocene epoch, and could be classified into four out pouring periods, according to the potassium\|argon age dating. The study on lithochemistry and age of the rocks in Qiangtang area suggest that Intracontinental subduction southward Qiangtang tectonic belt plays an important role to Cenozoic volcanism, and imply that the convective removal of the thicked lithosphere, which formed at the collision mountain\|building processes, are responsible for the formation of Cenozoic volcanic rocks, the earliest uplift of Tibetan plateau. and regional extension in Qiangtang area.
文摘The age and evolutional history of the Altyn Tagh fault and its role in the formation and uplift of the Qinghai—Tibetan plateau have been focused for years. Many geologists believe that the formation of the fault is a result of the collision between India and Asia. Some people thought that it should have formed earlier than Cenozoic but have no critical evidence. Here we report a preliminary result from our recent investigation on the volcanic rocks at the north end of the Altyn Tagh fault.1 The volcanic rocks on the north end of the Altyn Tagh fault The volcanic rocks are located on the north end of the Altyn Tagh fault, northern Qinghai—Tibetan plateau. The investigated volcano occurs in the Jiuxi basin, a Cretaceous and Tertiary depositional basin. It is about 300m×100m in size and form about a 100m high cliff above the folded Cretaceous strata. It likes relic neck of a volcano rather than a kind of widely distributed lava flow commonly seen in the northern Tibet. The country rocks are Cretaceous sandstone, silt and fine\|grained conglomerate. The cliff formed most likely due to the differing erosion between the hard volcanic rocks and soft rocks.
文摘Studied Volcanic rocks are zonally distributed between Qiangtang and Kunlun landasses, that is in the western part of Lazhulong\|Jinsajiang tectonic belt. It is bounded on the north by Yanghu\|Hohxil deep fult and on the south by Bairabu Co\|Ruolagangri deep fault. As component part of ophiolites in this belt, volcanic rocks mainly occuring within low\|grade metamorphic and thick flysch deposits of Lower Permian and Late Triassic, are associated with gabbro, diabase, ultramafites, radiolarian silicalites and limestones, consisting of basalts, dorgalites, picrites, basaltic\|andesites, andesites and a few pyroclastic rocks. This suit of volcanics\|bearing flysch deposits had been considered as Triassic or Late Triassic stratum and also called as “Ruolagangri Group” before.The basalts in this belt are characterized by having lower SiO\-2, higher TiO\-2(1 74%～4 78%, average 2 94%) and K 2O+Na 2O(mostly 3 50%～5 00%) contents, and usually Na 2O>K 2O. The total REE abundances in basalts which vary from 115 68×10 -6 to 323 66×10 -6 are relatively high, and all of their distribution patterns show moderately or strongly LREE\|enriched. The LREE/HREE ratios range from 8 74 to 14 41, (La/Yb) N from 9 53 to 19 56, and showing faint positive or no Eu anomaly. Incompatible trace elements such as Sr, Rb, Ba, Th, Ta, Nd, P, Zr, Hf etc. are relatively concentrated, whose contents usually are several times to several tens of MORB, while Yb, Y, Sc, Cr are obviously depleted. The characteristics of Petrochemistry and rare elementary geochemistry indicate that the volcanic rocks belong to series of alkaline or subalkaline basalt and show the features of alkaline—transitional basalt under the setting of continental rift or ocean island, and also similar to that of Late Carboniferous basalts in Chabu\|Chasang area of central Qiangtang and that of Permian Emeishang basalts in southwest of China.
文摘In these years,the Upper Jurassic andesitic volcanic reservoirs in Erlian basin,the Lower Cretaceous rhyolitic volcanic reservoirs in Songliao Basin,the Cretaceous rhyolitic,and the Paleogene basaltic and trachytic volcanic reservoirs in Bohai Bay Basin,and the basaltic volcanic reservoirs in Subei basin were discovered.With more and more volcanic oil and gas fields being discovered and developed,the volcanic rocks demonstrate a great petroleum potential in eastern basins of China.Five volcanic facies were identified in these basins,including volcanic conduit facies,explosive facies,effusive facies。
