We applied the material balance principle of the denudation volume and sedimentary flux to study the denudation-accumulation system between the Longmen Mountains （Mts.） and the foreland basin. The amount of sediment...We applied the material balance principle of the denudation volume and sedimentary flux to study the denudation-accumulation system between the Longmen Mountains （Mts.） and the foreland basin. The amount of sediment in each sedimentation stage of the basin was estimated to obtain the denudation volume, erosion thickness and deposit thickness since the Late Triassic Epoch, to enable us to recover the paleoelevation of the provenance and the sedimentary area. The results show the following： （1） Since the Late Triassic Epoch, the elevation of the surface of the Longmen Mts. has uplifted from 0 m to 2751 m, and the crust of the Longmen Mts. has uplifted by 9.8 km. Approximately 72% of the materials introduced have been denuded from the mountains. （2） It is difficult to recover the paleoelevation of each stage of the Longmen Mts. foreland basin quantitatively by the present-day techniques and data. （3） The formation of the Longmen Mts. foreland basin consisted of three stages of thrust belt tectonic load and three stages of thrust belt erosional unload. During tectonic loading stages （Late Triassic Epoch, Late Jurassic-Early Cretaceous, Late Cretaceous-Miocene）, the average elevation of Longmen Mts. was lower （approximately 700-1700 m）. During erosional unloading stages （Early and Middle Jurassic, Middle Cretaceous and Jiaguan, Late Cenozoic）, the average elevation of Longmen Mts. was high at approximately 2000-2800m.展开更多
The Taiwan mountain belt, one of the youngest orogenies in the world, is caused by the collision of the Luzon arc with the Eurasian margin, which leads to post-collisional extension and magmatism in the Northern Taiwa...The Taiwan mountain belt, one of the youngest orogenies in the world, is caused by the collision of the Luzon arc with the Eurasian margin, which leads to post-collisional extension and magmatism in the Northern Taiwan Volcanic Zone(NTVZ). The magma chamber process in this region has not previously been elucidated in detail. In this paper, the textural and compositional features of plagioclase phenocrysts in basalt from the Tatun Volcanic Group(TTVG) were studied to restrict the dynamics of magma system. Results show that the magma melts in TTVG are mainly sourced from the underlying MORB-like mantle wedge but influenced by incorporation of subduction components, causing the elevated Sr/Y and Ba/Y ratios in magma melts. The subduction components are mainly transported in the form of sediment melt. The plagioclase phenocrysts in the TTVG volcanic rocks are generally coarsely core-sieved with a clear rim. The An contents in the rims of plagioclase are much lower than those of cores, and elevated FeO concentrations are detected in the plagioclase rims. We propose there exists a double-layer magma chamber in this region. The core of the plagioclase was crystalized in the deeper quiescent magma chamber(~21 km), which was subsequently partially dissolved during the ascent of magma melt under H_(2)O-undersaturated condition, forming the typical coarsely sieved texture and synneusis. When this crystal-rich melt migrates into the shallower chamber, water saturation is reached and more sodic plagioclase formed as the rim of phenocryst. Due to the considerably higher fO_(2) in the shallow chamber than in the deeper one, and the distribution of Fe between plagioclase and melt positively correlates with fO_(2), the FeO content in the plagioclase rim elevates in conjunction with increasing fO_(2).展开更多
基金the Project of the National Natural Science Foudation of China (Grant No.41372114,41340005,41172162,40972083)
文摘We applied the material balance principle of the denudation volume and sedimentary flux to study the denudation-accumulation system between the Longmen Mountains （Mts.） and the foreland basin. The amount of sediment in each sedimentation stage of the basin was estimated to obtain the denudation volume, erosion thickness and deposit thickness since the Late Triassic Epoch, to enable us to recover the paleoelevation of the provenance and the sedimentary area. The results show the following： （1） Since the Late Triassic Epoch, the elevation of the surface of the Longmen Mts. has uplifted from 0 m to 2751 m, and the crust of the Longmen Mts. has uplifted by 9.8 km. Approximately 72% of the materials introduced have been denuded from the mountains. （2） It is difficult to recover the paleoelevation of each stage of the Longmen Mts. foreland basin quantitatively by the present-day techniques and data. （3） The formation of the Longmen Mts. foreland basin consisted of three stages of thrust belt tectonic load and three stages of thrust belt erosional unload. During tectonic loading stages （Late Triassic Epoch, Late Jurassic-Early Cretaceous, Late Cretaceous-Miocene）, the average elevation of Longmen Mts. was lower （approximately 700-1700 m）. During erosional unloading stages （Early and Middle Jurassic, Middle Cretaceous and Jiaguan, Late Cenozoic）, the average elevation of Longmen Mts. was high at approximately 2000-2800m.
基金funded by the Shandong Provincial Natural Science Foundation, China (No. ZR2019BD010)the National Natural Science Foundation of China (No. 42276085)+2 种基金Open Fund of the Key Laboratory of Marine Geology and Environment, Chinese Academy of Sciences (No. MGE2021KG01)Pilot National Laboratory for Marine Science and Technology (Qingdao) (No. JCZX202014)the Key Laboratory Submarine Geoscience and Prospecting Techniques, Ministry of Education, Ocean university of China。
文摘The Taiwan mountain belt, one of the youngest orogenies in the world, is caused by the collision of the Luzon arc with the Eurasian margin, which leads to post-collisional extension and magmatism in the Northern Taiwan Volcanic Zone(NTVZ). The magma chamber process in this region has not previously been elucidated in detail. In this paper, the textural and compositional features of plagioclase phenocrysts in basalt from the Tatun Volcanic Group(TTVG) were studied to restrict the dynamics of magma system. Results show that the magma melts in TTVG are mainly sourced from the underlying MORB-like mantle wedge but influenced by incorporation of subduction components, causing the elevated Sr/Y and Ba/Y ratios in magma melts. The subduction components are mainly transported in the form of sediment melt. The plagioclase phenocrysts in the TTVG volcanic rocks are generally coarsely core-sieved with a clear rim. The An contents in the rims of plagioclase are much lower than those of cores, and elevated FeO concentrations are detected in the plagioclase rims. We propose there exists a double-layer magma chamber in this region. The core of the plagioclase was crystalized in the deeper quiescent magma chamber(~21 km), which was subsequently partially dissolved during the ascent of magma melt under H_(2)O-undersaturated condition, forming the typical coarsely sieved texture and synneusis. When this crystal-rich melt migrates into the shallower chamber, water saturation is reached and more sodic plagioclase formed as the rim of phenocryst. Due to the considerably higher fO_(2) in the shallow chamber than in the deeper one, and the distribution of Fe between plagioclase and melt positively correlates with fO_(2), the FeO content in the plagioclase rim elevates in conjunction with increasing fO_(2).
