Volcanic activity was quite frequent during the deposition of the Late Carboniferous Ha’erjiawu Formation in the Santanghu Basin.The petrology and organic and inorganic geochemical indicators were used to investigate...Volcanic activity was quite frequent during the deposition of the Late Carboniferous Ha’erjiawu Formation in the Santanghu Basin.The petrology and organic and inorganic geochemical indicators were used to investigate hydrocarbon potential,paleoenvironmental conditions and organic matter enrichment of the mudstones.The results show that the oil generation capacity of the Ha’erjiawu Formation mudstones,which has abundant oil-prone organic matter(TypeⅡkerogen with hydrogen index values mainly ranging from 250 to 550 mg HC/g TOC)in mature stage(Tmax values mainly ranging from 435 to 450℃),is considerable.The Ha’erjiawu Formation was deposited in a dysoxic,freshwater-mildly brackish,and warm-humid environment.During its deposition,the Ha’erjiawu Formation received hydrothermal inputs.The volcanic hydrothermal activities played an important role in the organic matter enrichment.In addition,the total organic carbon(TOC)is significantly positively correlated with the felsic mineral content,but it is negatively correlated with the carbonate mineral content and C27/C29 ratios,indicating that terrigenous organic matter input also contributed to the primary productivity in the surface water.Therefore,the formation of the high-quality source rocks in the Ha’erjiawu Formation was jointly affected by the hydrothermal activity and the terrigenous organic matter input.展开更多
The Turpan-Hami and Santanghu basins are the late Paleozoic-Mesozoic-Cenozoicreworked intracontinental basins that superposed on the folded basement of the Paleozoic orogenicbelt. ^(40)Ar/^(39)Ar geochronological stud...The Turpan-Hami and Santanghu basins are the late Paleozoic-Mesozoic-Cenozoicreworked intracontinental basins that superposed on the folded basement of the Paleozoic orogenicbelt. ^(40)Ar/^(39)Ar geochronological study of the basalts developed in the basins reveals that theformation period is Permain (293—266 Ma). From geochemical comparison of the basalts, theSantanghu basalts exhibit a strong depletion in Nb and Ta, and a selective enrichment in HFSE,reflecting that the source region is influenced by the subducted components related to subduction ofthe ancient oceanic crust and characterized with ''lagged arc volcanic rocks''. In contrast, theTurpan-Hami basalts show a slight depletion in Nb and Ta, high Th/Ta ratio, similar to the basaltsformed in an intracontinental ex-tensional zone or in an initial rift. Combined with the formationperiod of the ophiolite and ophiolite melange zones and regional magmatic activities occurring onthe post-orogenic extensional background in northern Xinjiang, it can be inferred from thesegeochemical characteristics that the tectonic background for forming the Turpan-Hami and Santanghubasins is closely related to the regional extension after the continent-continent collisionalorogeny. The basalts of the two basins came from different sources on the post-orogenic extensionalbackground of the similar basin-forming dynamics. Although the settings are all intracontinentalrift, the source for the Santanghu basalts is obviously subjected to the metasomatism of thesubducted components, implying the existence of the previous subduction.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.41472111,41702127)。
文摘Volcanic activity was quite frequent during the deposition of the Late Carboniferous Ha’erjiawu Formation in the Santanghu Basin.The petrology and organic and inorganic geochemical indicators were used to investigate hydrocarbon potential,paleoenvironmental conditions and organic matter enrichment of the mudstones.The results show that the oil generation capacity of the Ha’erjiawu Formation mudstones,which has abundant oil-prone organic matter(TypeⅡkerogen with hydrogen index values mainly ranging from 250 to 550 mg HC/g TOC)in mature stage(Tmax values mainly ranging from 435 to 450℃),is considerable.The Ha’erjiawu Formation was deposited in a dysoxic,freshwater-mildly brackish,and warm-humid environment.During its deposition,the Ha’erjiawu Formation received hydrothermal inputs.The volcanic hydrothermal activities played an important role in the organic matter enrichment.In addition,the total organic carbon(TOC)is significantly positively correlated with the felsic mineral content,but it is negatively correlated with the carbonate mineral content and C27/C29 ratios,indicating that terrigenous organic matter input also contributed to the primary productivity in the surface water.Therefore,the formation of the high-quality source rocks in the Ha’erjiawu Formation was jointly affected by the hydrothermal activity and the terrigenous organic matter input.
文摘The Turpan-Hami and Santanghu basins are the late Paleozoic-Mesozoic-Cenozoicreworked intracontinental basins that superposed on the folded basement of the Paleozoic orogenicbelt. ^(40)Ar/^(39)Ar geochronological study of the basalts developed in the basins reveals that theformation period is Permain (293—266 Ma). From geochemical comparison of the basalts, theSantanghu basalts exhibit a strong depletion in Nb and Ta, and a selective enrichment in HFSE,reflecting that the source region is influenced by the subducted components related to subduction ofthe ancient oceanic crust and characterized with ''lagged arc volcanic rocks''. In contrast, theTurpan-Hami basalts show a slight depletion in Nb and Ta, high Th/Ta ratio, similar to the basaltsformed in an intracontinental ex-tensional zone or in an initial rift. Combined with the formationperiod of the ophiolite and ophiolite melange zones and regional magmatic activities occurring onthe post-orogenic extensional background in northern Xinjiang, it can be inferred from thesegeochemical characteristics that the tectonic background for forming the Turpan-Hami and Santanghubasins is closely related to the regional extension after the continent-continent collisionalorogeny. The basalts of the two basins came from different sources on the post-orogenic extensionalbackground of the similar basin-forming dynamics. Although the settings are all intracontinentalrift, the source for the Santanghu basalts is obviously subjected to the metasomatism of thesubducted components, implying the existence of the previous subduction.
