西准噶尔和布克赛尔古洋盆的厘定——来自和布克赛尔蛇绿混杂岩的锆石U-Pb年代学及地球化学证据

发布时间：2018-06-15 19:03

本文选题：西准噶尔 + 和布克赛尔蛇绿岩　；参考：《地质学报》2017年12期

【摘要】：本文对西准噶尔北部先前较少报道的和布克赛尔蛇绿混杂岩进行了系统的野外填图与室内分析测试研究。该套蛇绿混杂岩总出露面积约4km2,岩石组分主要包括蛇纹石化橄榄岩、辉石岩、辉长岩、辉绿岩、玄武岩、硅质岩、大理岩及火山碎屑岩围岩。蛇纹石化橄榄岩作为基质,其它蛇绿混杂岩组分均以断块或断片形式与基质呈不规则的断层接触,为典型的基质包裹团块接触关系。围岩、基质和团块均发生不同程度变形和蚀变,围岩和基质中劈理较为发育。对蛇绿混杂岩中辉长岩团块进行地球化学分析,显示上凸型稀土配分模式,(La/Yb)N为0.48~0.65,具有轻微的Eu负异常,高场强元素(Zr-Lu)以几乎不分异并贴近于MORB为特征,显示该蛇绿岩应为洋中脊(MOR)型。辉长岩团块的LA-ICP-MS锆石U-Pb定年结果为484±3 Ma,说明古洋壳形成于早奥陶世。和布克赛尔蛇绿混杂岩时代与属性的最新厘定,一方面暗示了博什库尔-成吉斯弧与扎尔玛-萨吾尔弧之间应发育一个至少在早奥陶世已经存在的古洋盆,可为西准噶尔北部构造演化研究提供重要线索;另一方面,该蛇绿混杂岩可以与邻区已报道的库吉拜、洪古勒楞等蛇绿混杂岩做很好的对比连接,而与查干陶勒盖蛇绿混杂岩在各项特征上存在某些差异,可以为西准噶尔北部构造缝合带的划定提供新的约束。
[Abstract]:In this paper, systematic field mapping and laboratory analysis of the previously little-reported and Buxer ophiolitic melange in the northern part of West Junggar have been carried out. The total exposed area of the ophiolite melange is about 4 km ~ 2. The rock composition mainly includes serpentine peridotite, pyroxenite, gabbro, diabase, basalt, siliceous rock, marble and volcanic clastic rock surrounding rock. The ophiolitic peridotite is used as the matrix, and the other ophiolitic melange components are in irregular fault contact with the matrix in the form of fault block or fragment, which is a typical contact relation of matrix mass. The surrounding rock, matrix and mass are all deformed and altered to varying degrees, and cleavage in the surrounding rock and matrix is relatively developed. Geochemical analysis of gabbro mass in ophiolite melange shows that the upper convex REE partition model is 0.48 ~ 0.65, with slight EU negative anomaly, and the high field strength element Zr-Lu) is almost indistinguishable and close to MORB. It is suggested that the ophiolite is of type Mor. The LA-ICP-MS zircon U-Pb dating of the gabbro mass is 484 卤3 Ma, indicating that the paleo-oceanic crust was formed in the early Ordovician. The latest determination of the age and properties of the Buxer ophiolite melange suggests, on the one hand, that there should be a paleo-oceanic basin between the Boshkul Chenggiz arc and the Zalma-Savour arc, which existed at least in the early Ordovician. On the other hand, the ophiolitic melange can be well compared with the reported ophiolite melange in the neighboring area, such as Kujiba, Honkuleleng and so on, which can provide important clues for the study of tectonic evolution in the northern part of West Junggar. However, there are some differences between Chagan Tolgoi ophiolite and Chagan ophiolitic melange, which can provide a new constraint for the delineation of the tectonic suture zone in the northern part of West Junggar.
【作者单位】：东北大学深部金属矿山安全开采教育部重点实验室;东北大学资源与土木工程学院;中国地质大学地球科学与资源学院;
【基金】：国家自然科学基金(编号41202161,41672217) 高校基本科研业务费(编号N140104003,N140104004)资助的成果
【分类号】：P587

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