黑龙江平顶山金矿赋矿花岗岩锆石U-Pb年龄、Hf同位素特征及其地质意义
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国家自然科学基金(41173034);中国地质调查局项目(1212011120342)


Zircon U-Pb ages, Hf isotopic characteristics and their geological implications of the ore-hosting granites in the Pingdingshan gold deposit, Heilongjiang Province
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    摘要:

    平顶山金矿床位于佳木斯地块与松嫩地块的衔接处北端,地处中亚造山带的东段。前人对该矿床的岩(矿)石物理化学特征及地质特征已进行了研究,但对与成矿密切相关的花岗岩缺乏系统的岩石学、地球化学和高精度年代学等方面的研究。本次研究通过锆石的LA-ICP-MS U-Pb定年、Hf同位素示踪以及全岩的主、微量元素测试,探讨了平顶山金矿区赋矿花岗岩的源区特征、形成机制和构造背景。矿区花岗岩包括早期的浅色中粒二长花岗岩和稍晚期的细粒黑云母二长花岗岩,两期花岗岩的锆石U-Pb年龄分别为271.7±2.3Ma和249.8±3.3Ma,对应的εHf(t)为-4.17~-0.58 和-4.98~-0.49,两阶段平均模式年龄tDM2分别为1432Ma、1457Ma,原始岩浆可能来源于中元古代增生的壳源物质的重熔。两期花岗岩均以高碱(Na2O+K2O)、富Al2O3、富集LREE和LILE(Rb、Ba、Th、U和K)、低MgO、贫HREE和HFSE(Nb、Ta、P和Ti)为特征,属高钾钙碱性系列的准铝质/过铝质I-型花岗岩,代表了火山弧-同碰撞环境。结合中亚造山带东段构造演化历史,我们认为平顶山金矿的花岗岩可能是古亚洲洋向北俯冲、闭合、华北克拉通与佳-蒙陆块碰撞产物。

    Abstract:

    Pingdingshan gold deposit is located within the Jiamusi massif and is adjacent to the Songnen massif. Several geophysical methods have been applied in an attempt to constrain the prospecting and significance of vein and pyrite. However, little concern was given over hosting granites which closely related to the Pingdingshan gold deposit. This study carried out the LA-ICP-MS zircon U-Pb ages, coupled with Hf isotopic determination, and measurement of bulk rock major and trace-elements from the hosting granites. The granites in the Pingdingshan gold deposit are composed of earlier light-colored medium-grained monzogranite and slightly later fine-grained biotite monzogranite with zircon U-Pb ages at 271.7±2.3Ma and 249.8±3.3Ma, respectively. The εHf(t) values for these two episodes of magmatism are at -4.17~-0.58 and -4.98~-0.49, which correspond to Hf two-stage model ages of 1432Ma and 1457Ma, respectively, suggesting that their parent magmas derived from the partial melting of Mesooproterozoic crust. Both earlier and later monzogranites are characterized by high Al2O3, K2O+Na2O, LREE and LILE (Rb, Ba, Th, U and K), and low MgO, HREE and HFSE (Nb, Ta, P and Ti). They are chemically high-K calc-alkaline rock series, and represent volcanic arc/ syn-collision I-type granites. Combined with the evolution history of the eastern segment of the Central-Asian Orogenic Belt, we consider that the granites in the Pingdingshan deposit formed from the north-ward subduction, closure of the Paleo-Asian Ocean, and collision of North China Craton with Jiamusi-Mongolia massif.

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包真艳,王建,杨言辰,王林,谢志鹏,宋樾,刘建国.2014.黑龙江平顶山金矿赋矿花岗岩锆石U-Pb年龄、Hf同位素特征及其地质意义[J].地质学报,88(3):407-420.
Bao Zhenyan, Wang Jian, Yang Yanchen, Wang Lin, Xie Zhipeng, Song Yue, Liu Jianguo.2014. Zircon U-Pb ages, Hf isotopic characteristics and their geological implications of the ore-hosting granites in the Pingdingshan gold deposit, Heilongjiang Province[J]. Acta Geologica Sinica,88(3):407-420.

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  • 收稿日期:2013-06-21
  • 最后修改日期:2013-11-02
  • 录用日期:2014-03-11
  • 在线发布日期: 2014-03-11
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