Gas hydrate drilling expeditions in the Pearl River Mouth Basin,South China Sea,have identified concentrated gas hydrates with variable thickness.Moreover,free gas and the coexistence of gas hydrate and free gas have ...Gas hydrate drilling expeditions in the Pearl River Mouth Basin,South China Sea,have identified concentrated gas hydrates with variable thickness.Moreover,free gas and the coexistence of gas hydrate and free gas have been confirmed by logging,coring,and production tests in the foraminifera-rich silty sediments with complex bottom-simulating reflectors(BSRs).The broad-band processing is conducted on conventional three-dimensional(3D)seismic data to improve the image and detection accuracy of gas hydratebearing layers and delineate the saturation and thickness of gas hydrate-and free gas-bearing sediments.Several geophysical attributes extracted along the base of the gas hydrate stability zone are used to demonstrate the variable distribution and the controlling factors for the differential enrichment of gas hydrate.The inverted gas hydrate saturation at the production zone is over 40% with a thickness of 90 m,showing the interbedded distribution with different boundaries between gas hydrate-and free gas-bearing layers.However,the gas hydrate saturation value at the adjacent canyon is 70%,with 30-m-thick patches and linear features.The lithological and fault controls on gas hydrate and free gas distributions are demonstrated by tracing each gas hydrate-bearing layer.Moreover,the BSR depths based on broad-band reprocessed 3D seismic data not only exhibit variations due to small-scale topographic changes caused by seafloor sedimentation and erosion but also show the upward shift of BSR and the blocky distribution of the coexistence of gas hydrate and free gas in the Pearl River Mouth Basin.展开更多
Objective Previous studies on adakitic rocks with high Sr/Y and La/Yb ratios have established that such rocks may form in a variety of tectonic settings through different petrogenetic processes including: (1) parti...Objective Previous studies on adakitic rocks with high Sr/Y and La/Yb ratios have established that such rocks may form in a variety of tectonic settings through different petrogenetic processes including: (1) partial melting of subducted young (〈25 Ma), hot and hydrated oceanic slab; (2) partial melting of thickened lower crust; (3) assimilation and fractional crystallization processes involving basaltic magma; (4) partial melting of delaminated lower crust; and (5) partial melting of hydrous garnet peridotite. The various origins for adakites provide important constraints on crustal growth and evolution throughout the Earth's history.展开更多
基金supported by the State Key Laboratory of Natural Gas Hydrate(No.2022-KFJJ-SHW)the National Natural Science Foundation of China(No.42376058)+2 种基金the International Science&Technology Cooperation Program of China(No.2023YFE0119900)the Hainan Province Key Research and Development Project(No.ZDYF2024GXJS002)the Research Start-Up Funds of Zhufeng Scholars Program.
文摘Gas hydrate drilling expeditions in the Pearl River Mouth Basin,South China Sea,have identified concentrated gas hydrates with variable thickness.Moreover,free gas and the coexistence of gas hydrate and free gas have been confirmed by logging,coring,and production tests in the foraminifera-rich silty sediments with complex bottom-simulating reflectors(BSRs).The broad-band processing is conducted on conventional three-dimensional(3D)seismic data to improve the image and detection accuracy of gas hydratebearing layers and delineate the saturation and thickness of gas hydrate-and free gas-bearing sediments.Several geophysical attributes extracted along the base of the gas hydrate stability zone are used to demonstrate the variable distribution and the controlling factors for the differential enrichment of gas hydrate.The inverted gas hydrate saturation at the production zone is over 40% with a thickness of 90 m,showing the interbedded distribution with different boundaries between gas hydrate-and free gas-bearing layers.However,the gas hydrate saturation value at the adjacent canyon is 70%,with 30-m-thick patches and linear features.The lithological and fault controls on gas hydrate and free gas distributions are demonstrated by tracing each gas hydrate-bearing layer.Moreover,the BSR depths based on broad-band reprocessed 3D seismic data not only exhibit variations due to small-scale topographic changes caused by seafloor sedimentation and erosion but also show the upward shift of BSR and the blocky distribution of the coexistence of gas hydrate and free gas in the Pearl River Mouth Basin.
基金financially supported by the National Nature Science Foundation of China(grant No. 41202037)
文摘Objective Previous studies on adakitic rocks with high Sr/Y and La/Yb ratios have established that such rocks may form in a variety of tectonic settings through different petrogenetic processes including: (1) partial melting of subducted young (〈25 Ma), hot and hydrated oceanic slab; (2) partial melting of thickened lower crust; (3) assimilation and fractional crystallization processes involving basaltic magma; (4) partial melting of delaminated lower crust; and (5) partial melting of hydrous garnet peridotite. The various origins for adakites provide important constraints on crustal growth and evolution throughout the Earth's history.