新疆东准噶尔喀姆斯特晚古生代沉积记录:物源和沉积作用研究

东准噶尔喀姆斯特下泥盆统阿拉比也巴斯他乌组和下石炭统卡姆斯特组代表陆壳增生不同阶段的沉积响应.碎屑岩碎屑组成模式和地球化学分析结果表明阿拉比也巴斯他乌组形成于大洋-活动大陆过渡型构造环境,物源区主要为发育在过渡型地壳之上的岩浆岛弧;卡姆斯特组形成于活动大陆型构造环境,物源区主要为大陆岛弧环境的切割岩浆弧.沉积相、相组合及生物生态等沉积特征显示两组的沉积环境分别为海底斜坡和海底扇中扇-外扇盆地平原.结合区域构造分析和地层对比研究,下泥盆统阿拉比也巴斯他乌组海底斜坡沉积是东准噶尔构造带早泥盆世弧后盆地沉积响应的主要记录,卡姆斯特组海底扇-海底平原沉积则主要记录了东准噶尔复合地体早石炭世晚期弧间残余海盆的沉积响应.两套沉积响应记录的环境演化受控于中亚型造山带复杂的造山作用.

LATE PALEOZOIC SEDIMENTARY RECORDS KEMUSTE AREA EASTERN JUNGGAR XINJIANG :PROVENANCE AND FACIES ANALYSES

The Alabiyebastaw and Kamuste Formations, in ages of Early Devonian and Early Carboniferous respectively, represent sedimentary responses of different stages of the crustal accretion in the Kamuste area, Eastern Junggar, Xinjiang. The sandstones of Alabiyebastaw Formation are composed of volcanic and sedimentary detritus, and subordinately, of plagioclase and quartz mineral fragments, reflecting a predominant undissected magmatic arc provenance. The geochemistry of sandstone mudstone suites further indicates a felsic intermediate igneous provenance, which constrained the Alabiyebastaw Formation having derived from a tectonic setting of differentiated oceanic continental margin island arc. Likewise, the geochemistry and sandstone petrography of the Kamuste Formation reflects mixed provenance signatures of dominant magmatic arcs and minor basement uplifts and subduction complexes, indicating a tectonic setting of differentiated continental island arc. The facies analysis indicates that the Alabiyebastaw and Kamuste Formations are two kinds of turbiditic successions deposited on a submarine slope and a submarine fan plain respectively. The features of petrography and geochemistry, combined with structural and stratigraphic analyses allow for a thorough evaluation of the provenance and tectonic setting of Devonian and Carboniferous sedimentary rocks. The submarine slope turbiditic deposits of the Alabiyebastaw Formation record the main sedimentary response of the early Devonian back arc basins of the Northern Junggar tectonic belt with the source of island arc detritus mainly portrayed as a northern fringing arc system; the submarine fan plain turbiditic and hemipelagic deposits of the Kamuste Formation record the main sedimentary response of the late Early Carboniferous inter arc relict sea basins of the Eastern Junggar composite terrane with source areas on both sides supplying detritus and particulate materials.