吐哈盆地中北部中侏罗统重矿物组合特征及对博格达山隆升过程的约束

The differential heavy mineral uplift of the Bogda Mountain： Constraints from the characteristic of Middle Jurassic deposits in the North-Central Turpan-Hami Basin

通过对吐哈盆地中北部中侏罗统重矿物组合特征分析发现，该区重矿物组合具有显著的分区特征。其中桃尔沟-胜南-吐南地区整个中侏罗世，重矿物以高含量的磁铁矿、赤铁矿为特征。七泉湖-胜金地区在西山窑组-三间房组沉积时期，重矿物以锆石和钛的氧化物为主；自七克台组沉积伊始，磁铁矿含量显著增加。三堡-鲁克沁地区在西山窑组沉积时期，重矿物以锆石和钛的氧化物为主；到三间房组-七克台组沉积时期，石榴石、磁铁矿含量明显增加。鄯勒-萨克桑地区西山窑组沉积时期重矿物以锆石和钛的氧化物为主；三间房组沉积以来，磁铁矿含量急剧增加。丘陵-丘东地区西山窑组-三间房组沉积时期，重矿物以高含量绿帘石为特征；七克台组沉积时期，转而以锆石和钛的氧化物为主。研究区中侏罗统重矿物组合演化特征显示，中侏罗世博格达山的隆升具有明显的分段性：Ⅰ段（西）在西山窑组沉积时期便已隆起，构成盆地物源区；西山窑晚期-三间房初期，博格达山Ⅲ段（东）开始快速隆升，导致三间房组沉积时期鄯勒-萨克桑地区磁铁矿含量剧增；而博格达山Ⅱ段（中）直到七克台组初期才开始隆升。

Based on the analysis of heavy mineral assemblages from Middle Jurassic in middle-northern Turpan-Hami Basin, it＇s found that heavy mineral assemblage characteristics vary from area to area. In Taoerg-Shengnan-Tunan area, its heavy minerals were mainly composed of magnetite and hematite during the whole Middle Jurassic. In Qiquanhu-Shengjin area, the main component of heavy minerals were zircon, Ti-oxides, and garnet during the deposition of the XishanyaoSanjianfang Formations, but the amount of magnetite increased dramatically in the Qiketai Formation. The heavy minerals in Sanbao-Lukeqin area were characterized by large zircon, Ti-oxide in the Xishanyao deposition and since the stage of Sanjianfang-Qiketai Formations, the content of magnetite and garnet increased significantly. In Sanle-Sakesang area, the heavy minerals were consisted of largely zircon and Ti-oxide during the development of Xishanyao Formation, but since the deposition of Sanjianfang Formation, the proportion of the magnetite increased remarkably. In Qiuling-Qiudong area, the heavy minerals were characterized by high content of epidote in the deposition of Xishanyao-Sanjianfang Formations and then turn to zircon, Ti-oxide in the Qiketai Formation. The variation of heavy mineral assemblages in North-Central Turapan-Hami Basin show that the uplift of Bogda Mountains in Middle Jurassic were characterized by distinct segmentation. The west segment （ Ⅰ ） of the Bogda has been uplifted before Xishanyao stage and was the main Provence for the Turpan Basin. By contrast, the East （ Ⅲ ） and middle segments （ Ⅱ ） of the Bogda experienced uplift and erosion at the Late Xishanyao stage-Early Sanjianfang stage and Early Qiketai stage,respectively.