准噶尔盆地东北缘卡拉麦里构造带盆内延伸方式及其对盆地基底性质的影响

An extension pattern of the Kalamaili structural belt in the Junggar Basin and its influence on the nature of the basin basement

卡拉麦里构造带位于准噶尔盆地东北缘,对于其向盆内延伸的方向、与盆地内构造带的关系等问题目前认识仍不明确,制约了对该盆地基底性质以及盆内石炭系火山岩储层大地构造属性的认识。为此,对该盆地东部白碱沟地区石炭系巴塔玛依内山组火山沉积地层进行了地质填图及SHRIMP锆石U-Pb原位定年,结合前人的研究成果,从火山机构与火山岩分布、火山活动时限等方面,对比了盆内及卡拉麦里构造带石炭系火山岩的地质特征,探讨了该构造带在盆内的延伸方式及其影响。结果表明:①白碱沟地区巴塔玛依内山组出露的流纹岩其SHRIMP锆石U-Pb定年结果为距今300.8±4.9 Ma,表明该区火山活动时间为晚石炭世晚期;②陆梁隆起与卡拉麦里构造带属同一条构造单元,其基底原型为一套增生型造山带;③陆梁隆起发育的2条SEENWW向中基性火山岩带是野马泉岩浆弧和哈尔里克岩浆弧在盆内的延伸,2条火山岩带之间为卡拉麦里蛇绿岩带;④陆东—五彩湾地区石炭系火山岩储层发育在南侧火山岩带中,其形成的大地构造环境为岛弧环境。

As for the Kalamaili structural belt located at the northeastern edge of the Junggar Basin, its extension direction and its re- lation with other structural belts in the basin are not ascertained, which restricts the cognitions on the nature of the basin basement and the geoteetonic properties of Carboniferous volcanic reservoirs. In view of this, geological mapping and SHRIMP zircon U-Pb dating were conducted on volcanic-sedimentary formations of Carboniferous Batamayineishan Formation in the Baijiangou area of the eastern Junggar Basin. Based on the previous research results, a comparative study was performed on the geologic characteristics of Carboniferous volcanic rocks within the basin and in the Kalamaili structural belt, in terms of volcanic edifice, volcanic distribution and volcanic activity timing. Then, the extension pattern of the structural belt in the basin and its influence were discussed. The fol- lowing conclusions are reached. First, based on SHRIMP zircon U-Pb dating, rhyolite exposure of the Batamayineishan Formation in the Baijiangou area is 300.8~4.9 Ma, which indicates that the volcanic activity in this area occurred at the late stage of Late Carbon- iferous. Second, the Luliang uplift and the Kalamaili structural belt exist in the same structural unit, and their basement is originally a set of accretionary orogens. Third, the two SEE-NWW intermediate-basic volcanic belts developed in the Luliang uplift are the ex- tensions of Yemaquan and Haerlike magmatic arcs in the basin, and between them is the Kalamaili ophiolite belt. And fourth, in the Ludong-Wucaiwan area, Carboniferous volcanic reservoirs are developed in the volcanic belts along the south flank, and they are of island-arc geotectonic origin.