西天山CuNi-VTiFe复合型矿化镁铁-超镁铁杂岩 ——哈拉达拉岩体成岩成矿背景特殊性讨论

西天山哈拉达拉镁铁-超镁铁杂岩为一CuNi-VTiFe复合型矿化岩体,主要由橄长岩、橄榄辉长岩、角闪辉长岩、辉长岩和辉绿岩组成。获得岩体中橄榄辉长岩SHRIMP锆石U-Pb年龄为308.8±1.9Ma,辉长岩SHRIMP锆石U-Pb年龄307.3±8.2Ma。岩石具堆晶结构、辉长-辉绿结构,岩体韵律层发育;各类岩石稀土和微量元素配分曲线模式相似,多具Eu,Sr正异常,它们可能为同一岩浆结晶分异演化的产物;Sr-Nd同位素特征(87Sr/86Sr初始比值=0.703913～0.705259,εNd(t)=4.00～8.42)表明原始岩浆来自于亏损地幔源区。推测哈拉达拉岩体形成于后碰撞造山早期伸展环境、叠加近同期地幔柱活动的特殊地质背景中。

A debate on the special circumstance of rock-forming and ore-forming of Haladala pluton, a mafic-ultramafic complex related to CuNi-VTiFe composite mineralization, in western Tianshan

Haladala pluton,a mafic-ultramafic complex related to CuNi-VTiFe composite mineralization in western Tianshan,consists of troctolite,olivine gabbro,hornblende gabbro and diabase.The SHRIMP zircon U-Pb age of 308.8±1.9Ma,307.3±8.2Ma for olivine gabbro and gabbro of the Pluton were obtained.The major rock types in the Haladala pluton show cumulate texture,gabbro-ophitic textures,and the pluton exhibits well-developed rhythmic layering.All the different types rock of the plutons have rather similar trace-element distribution and REE patterns with positive Eu,Sr abnormity mostly,and it suggests they were the results of crystallization differentiation of the similar or same magma.The geochemical characteristics of Sr-Nd isotope compsition,initial 87Sr/86Sr values=0.703913～0.705259,εNd(t)=4.00～8.42,show that the original magma came from depleted mantle source.The study proposes that the Haladala pluton was formed in an early post-collisional orogenic stage,overlaying the possible mantle plume in the same time.