Permian tectonic evolution of the Mudanjiang Ocean: Evidence from zircon U-Pb-Hf isotopes and geochemistry of a N-S trending granitoid belt in the Jiamusi Massif, NE China
Permian tectonic evolution of the Mudanjiang Ocean: Evidence from zircon U-Pb-Hf isotopes and geochemistry of a N-S trending granitoid belt in the Jiamusi Massif, NE China
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牡丹江洋二叠纪构造演化：佳木斯地块南北走向花岗岩带锆石U-Pb-Hf同位素和地球化学证据
DOI：
10.1016/j.gr.2017.05.017
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发表时间：
2017
影响因子：
6.1
通讯作者：
许文良
中科院分区：
文献类型：
--
作者：
董玉;葛文春;杨浩;毕君辉;王智慧;许文良
通过对佳木斯地块内5个二叠纪花岗岩体（明义岩体、驼窑子岩体、孟家岗岩体、横头山岩体和青北岩体）的LA-ICP-MS锆石U-Pb定年和地球化学（主量元素、微量元素和Hf同位素组成）分析，确定了它们的时代、岩石成因和构造演化。研究的花岗岩体由正长花岗岩、二长花岗岩和花岗闪长岩组成，侵位时间为早中二叠世（278-263 Ma）。这些花岗质岩体大多是高钾钙碱性和弱过铝质，并表现出一致的相关性，不同的氧化物与SiO2。它们都富含大离子亲石元素（例如，Rb、Th、K）和轻稀土元素，并且耗尽高场强元素（例如，Nb、Ta、Ti）和重稀土元素。它们的Hf同位素组成相对均一，εHf（t）值为-6.16 ~+2.95，两阶段模式年龄为1681 ~ 1111 Ma。根据它们的侵位时代、地球化学特征和Hf同位素组成，认为它们可能起源于成分相似但分馏程度不同的母岩浆，岩浆来源于角闪岩相镁铁质下地壳的部分熔融。结合前人对佳木斯地块和松嫩-张广才地块同期岩浆-构造活动的研究，认为在这两个地块中分布着两条南北向的二叠纪岩浆带。牡丹江洋板块向东俯冲到佳木斯地块之下，导致地壳熔融，产生了佳木斯地块二叠纪南北向花岗岩类。牡丹江洋板块向西俯冲于松嫩-张广才地块之下，引起松嫩-张广才地块东缘沿着二叠纪岩浆活动。综上所述，二叠纪前佳木斯地块与松嫩-张广才地块并未发生碰撞，牡丹江洋的构造演化符合双侧俯冲模式。
A combined study of LA-ICP-MS zircon U-Pb dating and geochemical analyses (major and trace elements, and Hf isotopic compositions) for five Permian granitic plutons (Mingyi, Tuoyaozi, Mengjiagang, Hengtoushan, and Qingbei plutons) from the Jiamusi Massif was carried out to determine their ages, petrogenesis, and tectonic evolution. The studied granitic plutons are composed of syengranites, monzogranites, and granodiorites, and they were emplaced in the Early-Middle Permian (278–263 Ma). These granitic plutons are mostly high-K calc-alkaline and weakly peraluminous, and show consistent correlations of different oxides versus SiO2. They are all enriched in large ion lithophile elements (e.g., Rb, Th, K) and light rare earth elements, and depleted in high field strength elements (e.g., Nb, Ta, Ti) and heavy rare earth elements. And they have relatively homogeneous Hf isotopic compositions, with εHf(t) values varying from − 6.16 to + 2.95 and two-stage model ages ranging from 1681 to 1111 Ma. According to their emplacement ages, geochemical characteristics, and Hf isotopic compositions, we conclude that these granitoids might be originated from parental magmas with similar compositions but evolved different degrees of fractionation, and their magmas were derived from the partial melting of amphibolite-facies mafic lower crust. These data, combined with previous studies on contemporaneous magma-tectonic activities in the Jiamusi Massif and Songnen-Zhangguangcai Range Massif, indicate that two paralleled N-S trending Permian magmatic belts are distributed in these two massifs. The eastwards subduction of the Mudanjiang oceanic plate beneath the Jiamusi Massif induced crustal melting to produce the studied Permian N-S trending granitoids in the Jiamusi Massif. Furthermore, westwards subduction of the Mudanjiang oceanic plate beneath the Songnen-Zhangguangcai Range Massif gave rise to Permian magmatism along eastern margin of the Songnen-Zhangguangcai Range Massif. Taken together, we suggest that the Jiamusi Massif and Songnen-Zhangguangcai Range Massif were not collided before the Permian, and a double-side subduction model is favored for the tectonic evolution of the Mudanjiang Ocean during the Permian.