花岗岩的成岩时代、地球化学特征和成因青海祁漫塔格地区虎头崖矿床Ⅵ矿带

摘要

利用 LA ICP MS 锆石 U Pb 法,测得与成矿有关的青海祁漫塔格地区虎头崖矿床Ⅵ矿带花岗岩的成岩年龄为(233.6±1.8)Ma(MSWD=1.2,n=17)。地球化学特征显示：花岗岩属高钾钙碱性、弱过铝质花岗岩；样品的稀土元素组成以总体右倾,轻、重稀土分异明显和具明显的负铕异常为特征；微量元素具有富集 Rb、Th、U、La、Nd 等大离子亲石元素,亏损 Ba、Sr、Nb、P、Ti 等元素的特点。Sr Nd 同位素组成特征显示,花岗岩的源区可能是富集岩石圈地幔。初步研究认为,虎头崖矿床Ⅵ矿带花岗岩可能形成于中、晚三叠世碰撞后碰撞的构造背景下。%Zircon LA ICP MS dating of the granite from the No.Ⅵ section of Hutouya deposit yields an emplacement age of (233.6 ± 1.8 )Ma (MSWD = 1.2,n = 17 ).The geochemical analysis indicates that the granite belongs to the weakly peraluminous granitic rocks,showing the nature of high-K calc-alkalic series.The rock has high REE content,and the chondrite-normalized REE distribution patterns show the characteristics of LREE enrichment,obvious LREE and HREE fractionation,and significant negative Eu anomaly.The trace element composition of the granite is enriched in Rb,Th,U, La,Nd and poor in Ba,Sr,Nb,P,Ti.The Sr Nd isotope composition and geochemical characteristics indicate that the magma source of the granite mainly derived from enriched lithospheric mantle.The data of this study indicate that the granite from the No.Ⅵ section of Hutouya deposit formed under a collision,and post-collision setting.