青海省拉水峡基性杂岩体地球化学特征及其对矿床成因的约束

Geochemical Characteristics of the Lashuixia Basic Complex in Qinhai Province and Its Constraints on Genesis of the Deposit

对与青海省拉水峡铜镍硫化物矿床密切相关的基性杂岩体的地球化学研究表明,该岩体以低Ti、亏损Nb和Ta、富集轻稀土元素和大离子亲石元素为特征。结合其同位素组成特征,提出该岩体的形成与祁连山及其邻区460～440Ma时期俯冲向碰撞转换的作用有关,岩浆起源于富集的岩石圈地幔,并在高位岩浆房中遭受了地壳的混染作用,从而导致岩浆中Si的增加,并引起富硫化物矿浆与富硅酸盐岩浆的不混熔作用。

The Lashuixia Ni-Cu sulfide deposit is an important Cu-Ni-rich deposit in Qinhai Province. Geochemical studies of the basic complex closely associated with the deposit show that it is characterized by low Ti, depletion of Nb or Ta, and enrichment of LREE and large lithosphile elements. Combined with their isotope geochemistry, it is concluded that the formation of the basic complex is related to the conversion from subduction to collision between the Qilian Mountains and their adjacent areas at 460 - 440 Ma. The magma was derived from the enriched lithospheric mantle, contaminated by crustal materials within the high-level magma chamber. This process led to the increasing amount of Si, and triggered the immiscibility between the sul- fides-rich liquid and the silicate-rich liquid.