西天山菁布拉克基性杂岩体的地球化学特征

Geochemistry of the Qingbulake Basic Complex in Western Tianshan

对与特克斯县菁布拉克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、富集大离子亲石元素和微富集轻稀土元素为特征。结合其同位素特征,提出该岩体的形成与南天山洋板块向中天山板块俯冲碰撞作用有关,岩浆起源于MORB源的亏损地幔,由于南天山洋壳向亏损地幔的俯冲,导致岩浆具有岛弧岩浆的特点。在侵位过程中遭受地壳和围岩的混染作用较弱。

Only the small Qingbulake Ni--Cu sulfide deposit was discovered in western Tianshan, however, as part of the mafic--ultramafic intrusion belts in northern Xinjiang, there developed about tens of intrusions in the Qingbulake basic rock belt. Geochemical studies of the Qingbulake basic complex closely associated with the deposit show that it is characterized by low content of Ti, depletion of Nb and Ta, enrichment of large lithosphile elements and slight enrichment of LREE. The magma also displays some features of island arc magma. Combining with their isotope geochemistry, we propose that the formation of the complex may closely relate to the subduction of the southern Tianshan oceanic crust to the central Tianshan plate. The magma was derived from the MORB type depleted mantle, and was contaminated or slightly contaminated by the crust or wall-rock during the emplacement.