内蒙古蒙国特闪长岩体地球化学特征及成因  

GEOCHEMICAL FEATURES AND PETROGENESIS OF MENGGUOTE DIORITIC PLUTON IN INNER MONGOLIA

作　　者：赵飞 刘懿伟 程建军 张健 孙发伟 

机构地区：[1]甘肃省地矿局第二地勘院,甘肃兰州730020

出　　处：《甘肃地质》2015年第3期16-24,共9页Gansu Geology

基　　金：内蒙古自治区地质勘查基金项目(NMKD2013-28)

摘　　要：蒙国特闪长岩体位于宁夏与内蒙古交界的贺兰山北段，岩石类型单一，为黑云母闪长岩，SiO。含量为52．99％-55．48％，Na20含量为2．85％-3．13％，K2O／Na2O平均为1．16，相对富钾贫钠；里特曼指数盯介于3．01-4．30，含铝指数A／CNK和碱铝指数NK／A均小于1，属准铝质碱性岩。∑REE为898．04×10-6-1267．82×10-6,LREE强烈富集，（La／Yb）。为23．95～39．98，中等负Eu异常，扭u为0．48—0．71，δCe为71．03-1．07。大离子亲石元SRb、Ba及La、Ce、Pb相对富集，高场强元素Th、U、Nb、Ta、P、Ti及sr强烈亏损，显示大陆地壳参与了岩浆作用过程。综合研究认为蒙国特闪长岩体属I型花岗岩，是地幔底侵作用导致加厚下地壳发生部分熔融的产物，形成于板块碰撞后隆起的构造环境。Mengguote dioritic pluton is situated in the northern segment of Helan Mountain between Ningxia Province and Inner Mongolia. The pluton consists of biotite diorites with Si02 contents of 52.99%-55.48%, high K2O but low Na2O contents of 2.85%-3.13% and corresponding K2O/Na2o average value of 1.16, with Rittmann Index of 3.01-4.30, low A/CNK and NK/A values （both〈l）,which belongs to aluminous alkaline rocks. These rocks have ∑ REE contents of 898.04×10-6-1267.82×10-6,and enrichment in LREE with （La/Yb）N of 23.95-39.98,and moderate negative Eu anomalies （8Eu=0.48-0.71）,δCe=1.03-1.07. They are enrichment in LILEs （Rb,Ba,La,Ce and Pb） but depletion in HFSE （Th,U,Nb,Ta,P,Ti and Sr）, indicating that lower continental crust was involved in the magmatism. Analysis data suggest that the Mengguote diorites were involved in a upheaval setting after plate collision, they are I-type granites which were produced by mixing between the crustal magma derived from thickened lower crust and the underplating mantle magma.

关 键 词：蒙国特闪长岩体 I型花岗岩 地幔底侵作用 地壳深熔作用 板块碰撞后隆起 

分 类 号：P588.122[天文地球—岩石学]