Geodynamic Indications on Igneous Rocks of Transitory Geologic Setting during the Late Hercynian in North Tarim Basin  

作　　者：汤良杰 黄太柱 崔泽宏 杨素举 朱毅秀 金仙梅 

机构地区：[1]State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum [2]Key Laboratory for Hydrocarbon Accumulation Mechanism, Ministry of Education [3]Basin & Reservoir Research Center, China University of Petroleum [4]Northwest Oilfield Company, SINOPEC [5]Research Institute of Petroleum, China Exploration & Development

出　　处：《Journal of China University of Geosciences》2008年第6期577-590,共14页中国地质大学学报（英文版）

基　　金：supported by the National Natural Science Foundation of China (Nos. 40672143, 40472107, 40172076);the National Basic Research Program (Nos. 2005CB422107, G1999043305);Project of Northwest Oilfield Company, SINOPEC (KY-S-2006-014)

摘　　要：Basic and intermediate-acidic igneous rocks were developed during the late Hercynian in North Tarim basin. The geochemistry characteristics of the rocks show that basic volcanic rock has K2O/Na2O = 0.18-0.61 〈 1 and falls into a category of basalt of sodium system. The rocks contain enriched large-ion lithophile elements （LILE） （K, Rb, Ba, Th） and high-field strength elements （HFSE） （Nb, Ta, Ti, Zr, P）, with the magmatic material from the upper mantle. The intermediate-acidic volcanicrocks have σ = 1.91-2.96 〈 3.3, K2O/Na2O = 1.25-1.59 〉 1, as well as the enriched LILE and depleted HFSE （Nb, Ta, Ti, P）, presenting the same trace element compositions and characteristics as in the granitic rocks of South Tianshan Mt.; they are either shoshonitic igneous rocks or high-K calc-alkaline igneous rocks, with a distinct crust-derived component feature. The comprehensive analyses on the characteristics of the trace elements, the graphic tectonic discrimination, and the distribution features of the two types of igneous rocks show that they were formed under different tectonic settings and geodynamic environments： the basalt was formed in the active rifting period when the active mantle upwelling caused the thinning of lithosphere; the intermediateacidic volcanic-intrusive rock was formed in the island arc area of the active continental margin in North Tarim; the formation is associated with the plate subduction during the course of South Tianshan Ocean closure--the subduction of Middle Tianshan Mountain toward the Tarim plate. The basic and intermediate-acidic igneous rocks reveal a tectonic regime of extension-extrusion transition, which is significant in determining the key tectonic revolution period of North Tarim basin.Basic and intermediate-acidic igneous rocks were developed during the late Hercynian in North Tarim basin. The geochemistry characteristics of the rocks show that basic volcanic rock has K2O/Na2O = 0.18-0.61 〈 1 and falls into a category of basalt of sodium system. The rocks contain enriched large-ion lithophile elements （LILE） （K, Rb, Ba, Th） and high-field strength elements （HFSE） （Nb, Ta, Ti, Zr, P）, with the magmatic material from the upper mantle. The intermediate-acidic volcanicrocks have σ = 1.91-2.96 〈 3.3, K2O/Na2O = 1.25-1.59 〉 1, as well as the enriched LILE and depleted HFSE （Nb, Ta, Ti, P）, presenting the same trace element compositions and characteristics as in the granitic rocks of South Tianshan Mt.; they are either shoshonitic igneous rocks or high-K calc-alkaline igneous rocks, with a distinct crust-derived component feature. The comprehensive analyses on the characteristics of the trace elements, the graphic tectonic discrimination, and the distribution features of the two types of igneous rocks show that they were formed under different tectonic settings and geodynamic environments： the basalt was formed in the active rifting period when the active mantle upwelling caused the thinning of lithosphere; the intermediateacidic volcanic-intrusive rock was formed in the island arc area of the active continental margin in North Tarim; the formation is associated with the plate subduction during the course of South Tianshan Ocean closure--the subduction of Middle Tianshan Mountain toward the Tarim plate. The basic and intermediate-acidic igneous rocks reveal a tectonic regime of extension-extrusion transition, which is significant in determining the key tectonic revolution period of North Tarim basin.

关 键 词：late Hercynian igneous rock element geodynamics North Tarim basin. 

分 类 号：P618.13[天文地球—矿床学]