准噶尔盆地南缘小泉沟群沉积物源特征及构造-环境分析

Analysis of Sedimentary Provenance and Environment of Xiaoquangou Group in the Southern Margin of Junggar Basin

通过多种物源分析方法综合研究表明,准噶尔盆地南缘小泉沟群(T2-3x)物源区主要来自火山弧物缘区;盆地南缘东段重矿物组合特征表明,母岩为中酸性岩浆岩和中低级变质岩,物源区应为南部的博格达山。西段重矿物组合表明,物源区母岩应为中低级变质岩-中酸性岩浆岩和沉积岩,表明北天山隆起后曾一度成为研究区主物源。砾石成分分布表明石炭系主物源不是来自伊林哈比尔尕山,而是来自伊林哈比尔尕山以南至中天山地区;花岗质糜棱岩砾石表明位于中天山北缘韧性剪切带也可能为盆地另一物源区。总之,研究区在中-晚三叠世处于准平原化构造作用阶段,物源主要来自博格达山和伊林哈比尔尕山,但由于沉积区与物源区之间地形相差小,属于准平原环境。构造环境为活动大陆边缘或大陆弧区,沉积环境主要呈现为温暖-湿润环境下的湖泊沉积。

On the basis of systematic provenance analyses,the result showed that ancient flow direction of the Middle-late Triassic was totally SSW or SSE in the southern margin of Junggar Basin.The provenance area was sourced from the marginal areas of volcanic arc.The heavy mineral assemblage characteristics in the east of southern margin of Junggar Basin indicated that mother rocks were intermediate-acidic igneous and low-grade metamorphic rocks.The Bogda Mountain in the south of Junggar Basin was considered to be the source area.The heavy mineral assemblage from the west of the basin indicated that the mother rocks in the source area were the intermediate-acidic igneous,low-grade metamorphic and sedimentary rocks.This further indicated that the North Tianshan had been the primary source area after it was uplifted.Gravel composition distribution showed that the Yilinhabierga Mountain was not the main source area,but came from the south of Yilinhabierga Mountain and reached the Middle Tianshan Area.The occurrence of a small amount of granitic mylonite also suggested that the ductile shear zone located in the northern Tianshan Fault Zone was possibly the other source area.In summary,during the Middle-late Triassic,the study area is subjected to the peneplain tectonic evolution,and the Yilinhabierga and Bogeda Mountains are still source areas of the southern margin of Junggar Basin.Nonetheless,terrain differentiation between source area and deposition area is very small,it belongs to peneplain environment.The tectonic environment of the study area is mainly influenced by active continental margin or continental arc areas,and deposits are primarily deposited in lacustrine environments under warm and humid climate.