滇西腾冲地块石炭纪勐洪群碎屑沉积岩物源信息及构造归属

The Tengchong block that is located to the west of the Nujiang Fault is at a key geographic position which connects the Tibetan Plateau to the north, the other blocks of SE Asian to the south, and the Baoshan block to the east. It is indicated that the Tengchong block is originated from the eastern Gondwana; however, the tectonic affinity with Indian Gondwana or Australian Gondwana is still under debate. Thus, the Carboniferous Menghong Group, the most wide-spread distinctive Gondwana-affinity deposits in the Tengchong block, will be chosen to study the detrital zircon U-Pb ages and Hf isotopes. These data, combined with the sedimentary characteristics of the Menghong Group, will be used to discriminate the potential source areas and therefore to study the tectonic origin of the block. Together with results from similar works of the related regions, this study will be useful for the interpretation the tectonic relation of different heterogeneous blocks from the Tibetan Plateau and its southeast margin, and also helpful for the understanding of the tectonic evolution of the Gondwana continental margin.

滇西怒江断裂以西的腾冲地块地处北接青藏高原，南连东南亚其他块体，东与保山地块相对的关键地带。现有研究表明腾冲地块源自东冈瓦纳大陆，但其具体的构造亲缘性（印度大陆或西澳大利亚大陆）至今仍颇富争议。针对这一问题，本研究以腾冲地块中广泛发育的亲冈瓦纳陆块标志性地层——石炭纪勐洪群为研究对象，拟系统分析在不同位置出露的该群中碎屑锆石U-Pb年龄及Hf同位素组成特征，结合该群沉积学特征，确定碎屑沉积沉积岩可能的物质来源，并藉此识别腾冲地块的来源及构造归属。通过本项目的研究，结合区域已有相关研究结果，可系统的判定青藏高原及东南缘不同块体的构造亲缘关系，深入理解冈瓦纳陆缘演化的动力学机制。

该项目系统研究了滇西腾冲地块及邻区古生代沉积记录的锆石U-Pb年龄及Hf同位素，并藉此判断不同块体性质及在早古生代的起源，及在青藏高原聚合、隆升过程中所扮演的角色。研究表明，腾冲地块起源于东冈瓦纳印度陆缘；保山地块其东部边界为柯街断裂以东的澜沧江缝合带，与腾冲地块一致，保山地块起源于东冈瓦纳印度陆缘；确定了点苍山存在强烈的新元古代岩浆作用，点苍山为环Rodinia西北缘陆缘弧的一部分；首次在崇山地区确定新元古代中期岩浆作用的存在。