Geohronology and Geochemistry Characteristics of the Granitic Mylonitic Gneiss in the Zhalantun Haduohe Area of the Northern Great Xing′an Range
Geohronology and Geochemistry Characteristics of the Granitic Mylonitic Gneiss in the Zhalantun Haduohe Area of the Northern Great Xing′an Range
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2013
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通讯作者：
G. Fen
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作者：
G. Fen
哈多河地区花岗质糜棱片麻岩是一套变质花岗质岩石，主要由细粒黑云母二长花岗岩糜棱片麻岩、细粒黑云母花岗质糜棱片麻岩和细石榴云母花岗质糜棱片麻岩组成。地球化学研究结果表明，SiO2值范围为66.4%~ 74.52%，K_2O +Na_2O范围为7.36%~ 8.84%，SiO_2值范围为66.4%~ 74.52%，K_2O +Na_2O范围为7.36%~ 8.84%。Al 2 O3值为13.43%~ 15.74%，A/CNK=0.974~ 1.092，属高钾钙碱性、准铝质~弱过铝质岩石，稀土元素配分模式为右斜线形配分模式，具弱负Eu异常，高稀土总量（ΣREE =94.15×10~（-6）~164.30×10~（-6）），LREE富集，HREE亏损，微量元素特征为强烈富集大离子亲石元素，如Rb、Ba、U、K等，亏损Ta、Nb、P、锆石U-Pb测年结果表明，岩浆形成可分为两期：第一期为320 Ma左右，代表岩石为细粒黑云母花岗质糜棱岩片麻岩和细粒石榴云母花岗质糜棱岩片麻岩;第二阶段为304 Ma左右，代表岩石为细粒黑云母二长花岗质糜棱岩质片麻岩，结合岩相学特征，年代学和岩石地球化学特征表明，花岗质糜棱岩片麻岩的原岩为高钾钙碱性I型花岗岩，形成于晚石炭世兴安地块与松嫩地块碰撞后环境，在早二叠世晚期，由于兴安地块与松嫩地块的后碰撞作用，遭受了较强的韧脆性变质变形作用。
The granitic mylonitic gneiss in Haduohe area is a set of metamorphic granitic rocks is mainly composed of fine grained biotite monzonitic granitic mylonitic gneiss,fine grained biotite granitic mylonitic gneiss and fine garnet mica granitic mylonitic gneiss.The results of geochemical study indicate that SiO_2 values are in the range of 66.4%~74.52%,K_2O+Na_2O between 7.36%~8.84%,Al_2 O_3 values in the range of 13.43%~15.74%,A/CNK=0.974~1.092,suggesting that it belongs to high-K calc-alkaline and quasi-aluminous to weakly peraluminous rocks.The chondrite-normalized REE patterns demonstrate right-oblique linear REE patterns with weak negative Eu anomalies,higher total rare-earth content(ΣREE =94.15×10~(-6)~164.30×10~(-6)),and LREE enrichment and HREE depletion.The trace element is characterized by a strong enrichment in large ion lithophile elements,such as Rb,Ba,U,K et al,depletion in Ta,Nb,P,Ti et al.The zircon U-Pb dating results indicate that the magma formation can be divided into two periods:the first period is around 320Ma,the representative rock is fine grained biotite granitic mylonitic gneiss and fine garnet mica granitic mylonitic gneiss;and the second period is around 304Ma,the representative rock is fine grained biotite monzonitic granitic mylonitic gneiss.Combined with petrography,chronology and rock geochemical characteristics,the protolith of the granitic mylonitic gneiss is high-K calc-alkaline I type granite which formed in the post-collision environment of Xing'an block and Songnen block during Late Carboniferous,and then suffered relatively strong ductile brittle metamorphism and deformation during Late Early Permian by the post-collision of Xing'an block and Songnen block.