| Differentiation Mechanism and Evolution of High-level Magma Chamber at Xiangshan,China |
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| 摘 要： | The calc-alkaline volcanic magmas,which formed the Mesozoic uraniferous volcanic complex of Xiangshan,resulted from partial melting of the mixture of lower crust and enriched mantle with a high mixing proportion in a specific tectonic setting such as active continental margin or ocean-continent collision zone.The preliminary concentrations of Uand Th occur in low-degree par-tial melts.Only small part of these melts was rapidly extracted and erupted and most intruded into the high-level magma chamber(depth:12-13 km) of the compressed upper lithosphere ,in which occurred a strong differentiation which would resulted in strong preconcentrations of the high-hygromagmaphile elements U and Th associated with strong depletion of the 3-d transition ele-ments Ti,Sc,Co,Zr,etc.At the final stage of subduction of the West-Pacific-Kula plate towards the Asian continental plate,the regional tectonic environment was transformed from a compressive in-to a tensional setting.The strongly differentiated,U(and Th) enriched silicic alkalic magmas in high level magma chamber extensively erupted,extruded and intruded.The hydrothermal fluids released as a result of late volcano-degassing and dewatering during crystallization-solidification of magmas,re-sulted in the remobilization,leaching,migration and reconcentration of uranium ,which had been preconcentrated in volcanic rocks.Therefore,specific regional petrogeochemical criteria are expected for the uraniferous volcanic series.
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| 关 键 词： | 岩浆房 火山岩 中生代 锶同位素 稀土元素 铀 |
Differentiation mechanism and evolution of high-level magma chamber at Xiangshan,China |
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| Authors: | Linqi Xia Zuchun Xia Cheng Zhang R Clocchiatti J L Joron J Dardel |
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| Institution: | (1) Xi’an Research Institute of Geology and Mineral Resources, Ministry of Geology and Mineral Resources, China;(2) Laboratoire “Pierre Süe”, C. E. N., Saclay, France;(3) Commissariat à L’Energie Atomique, France |
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| Abstract: | The calc-alkaline volcanic magmas, which formed the Mesozoic uraniferous volcanic complex of Xiangshan, resulted from partial
melting of the mixture of lower crust and enriched mantle with a high mixing proportion in a specific tectonic setting such
as active continental margin or ocean-continent collision zone. The preliminary concentrations of U and Th occur in low-degree
partial melts. Only small part of these melts was rapidly extracted and erupted and most intruded into the high-level magma
chamber (depth: 12–13 km) of the compressed upper lithosphere, in which occurred a strong differentiation which would resulted
in strong preconcentrations of the high-hygromagmaphile elements U and Th associated with strong depletion of the 3-d transition
elements Ti, Sc, Co, Zr, etc. At the final stage of subduction of the West-Pacific-Kula plate towards the Asian continental
plate, the regional tectonic environment was transformed from a compressive into a tensional setting. The strongly differentiated,
U (and Th)-enriched silicic alkalic magmas in high level magma chamber extensively erupted, extruded and intruded. The hydrothermal
fluids released as a result of late volcano-degassing and dewatering during crystallization-solidification of magmas, resulted
in the remobilization, leaching, migration and reconcentration of uranium, which had been preconcentrated in volcanic rocks.
Therefore, specific regional petrogeochemical criteria are expected for the uraniferous volcanic series.
Project supported by the National Natural Science Foundation of China. |
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