豫西崤山后河岩体LA-ICP-MS锆石U-Pb定年及其地质意义

LA-ICP-MS Zircon U-Pb Dating of the Houhe Granite and its Geologic Implication in Xiao Mountain, Western Henan Province

与豫西小秦岭和熊耳山地区相类似，崤山北部也出露一系列中酸性小岩体，但与之相关的成矿作用明显较弱，因此长期未获得应有的关注。崤山北部小岩体的形成时代与区域成岩成矿时代之间的匹配关系对其深部构造演化研究及成矿潜力评价具有重要意义，鉴于此，作者对后河岩体进行了LA—ICP—MS锆石U-Db定年。后河岩体定年样品HH01的岩性为中一细粒黑云母二长花岗岩，30个锆石测点中有27个测点的测定值位于207PB/235U-206Pb/238U一致线上，相应的206Pb/238U年龄介于124～134Ma之间，加权平均年龄为128±1Ma（MSWD=I．02），属早白垩世。后河岩体是岩石圈拆沉作用的产物，其形成时代处在东秦岭地区广泛而强烈的成岩成矿作用时限内，且显示了Au、Ag、Cu、Mo、W等元素的异常富集，具有较大的内生金属成矿潜力。

There are several small intermediate and acid intrusions in north Xiao Mountain, which is similar to Xiaoqinling and Xiong＇ er Mountain. The mineralization realated to the small intrusions in Xiao Mountain, how- ever, is weaker obviously than in Xiaoqinling and Xiong＇ er Mountain, and research work on the small intrusions in Xiao Mountain is limited. The match relationship between ages of the small intrusions in Xiao Mountain and regional formation time of intermediate and acid intrusions and ore deposits has become important to understand its deep dynamic process and esitmate mineralization potential. The zircon U-Pb dating method of LA-ICP-MS was used to conform the age of Houhe granite. The sample of HH01 used to be dated from the Houhe body is me- dium- fine grained biotite monzonitic granite. There are 30 zircon spots were analysed, 27 results of them are in concord with the 207PB/235U-206Pb/238U trendline. Their 206Pb/238U ages are from 124 Ma to 134 Ma, and the weighted average age is 1284-1 Ma, which has suggested that the Houhe body was formed in early Cretaceous. The Houhe body is the product of lithosphere delamination in early Cretaceous, and the formation age of the Houhe body falls into time interval of extensive and intensive endogenetic mineralization in east Qinling orogen belt. Samples from the Houhe body have displayed obvious enrichment in Au, Ag, Cu, Mo and W. It was considered that the Houhe body has greatly endogenetic mineralization potential.