滇西漕涧地区崇山造山带伟晶岩的发现与地质意义  

The discovery of pegmatite of the Chongshan orogenic belt in the Caojian area, Western Yunnan and its geological significance

作　　者：黄亮 吴嘉林 王晓林 熊波 浦涛 朱勋早 方雄 HUANG Liang;WU Jia-lin;WANG Xiao-lin;XIONG Bo;PU Tao;ZHU Xun-zao;FANG Xiong(Yunnan Institute of Geological Survey,Kunming 650216,China;MLR Key Laboratory of Sanjiang Metallogeny and Resources Exploration and Utilization,Kunming 650051,China)

机构地区：[1]云南省地质调查院,云南昆明650216 [2]国土资源部三江成矿作用及资源勘查利用重点实验室,云南昆明650051

出　　处：《矿物学报》2020年第5期584-594,共11页Acta Mineralogica Sinica

基　　金：中国地质调查局地质调查项目(编号:DD20160345-02,DD20160016-11);云南省地勘基金项目(编号:D201901)。

摘　　要：在滇西大理漕涧地区地质调查期间对崇山造山带的岩浆岩进行调查研究,新发现了一套白色伟晶岩。该伟晶岩与母岩相伴呈条带状和局部网纹状,并组合成一岩浆混合岩带,根据岩浆源差异,可细分为二长花岗质和碱长花岗质2类,其中以二长花岗质为主体。锆石U-Pb年代学测试表明,LA-ICP-MS年龄为18.66~34.47 Ma,形成于始新世(末期)—中新世(早期),显示伟晶岩为长时间持续性的熔融作用所成。地球化学研究表明,伟晶岩为(高钾)钙碱性系列和钾玄质系列的过铝质花岗岩类,LREE中等富集,HREE平缓和较弱亏损,富集Rb、Th和亏损K、Ba、Hf、Zr等元素;R2-R1图解、A-B图解和Sr-Yb图解的投图结果显示,伟晶岩主体与喜马拉雅造山晚期阶段有关,形成于低压-极低压力条件和深部地壳物质的减压熔融过程。综合研究认为,伟晶岩为崇山造山带喜马拉雅造山晚期阶段的快速隆升过程的岩浆响应,其熔融作用的结束时间可能指示了崇山造山带快速隆升阶段的结束,且约为18.66 Ma。During the geological survey in the Caojian area, Dali Prefecture, western Yunnan, the authors had investigated and studied magmatic rocks in the Chongshan orogenic belt, and found a new set of white pegmatite whose main bodies are associated with the parent rock in forms of intercalated bands and local reticulated bands in a mixed magmatic rock zone. According to the difference of magma sources of pegmatites, there are two types of pegmatites, including the monzonitic granitic and alkaline granitic pegmatites, with majority of the monzonitic granitic pegmatite. The LA-ICP-MS zircon U-Pb dating ages of 34.47-18.66 Ma show that pegmatites were formed in a period from Eocene(late stage) to Miocene(early stage), indicating that the pegmatites were formed by magmas derived from long-term persistent partial melting. Geochemical studies show that the pegmatites belong to peraluminous granites of(high potassium) calc-alkaline series and shoshonitic series, with moderately enriched LREE, gently and weakly depleted HREE, enriched Rb and Th and depleted K, Ba, Hf, and Zr. The plotted results of R2-R1, A-B, and Sr-Yb diagrams show that the main body of pegmatites was mainly formed, in association with the late Himalayan orogeny, by the decompression melting process of crustal materials in depth under conditions of low pressure to extremely low pressure. Based on the comprehensive research, it is believed that the pegmatite represents a magmatic response of the rapid uplift process of the late Himalayan orogenic stage in the Chongshan orogenic belt. The end time of about 18.66 Ma for its melting process may indicate that the rapid uplift stage of the Chongshan orogenic belt was ended at that time.

关 键 词：崇山造山带 伟晶岩 喜马拉雅期 始新世 中新世 造山晚期 熔融作用 隆升 

分 类 号：P581[天文地球—岩石学] P597[天文地球—地质学]