东秦岭160~140 Ma Cu(Mo)和Mo(W)矿床磷灰石成分特征
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中国地质科学院矿产资源研究所 国土资源部成矿作用与资源评价重点实验室,中国地质科学院地质研究所,中国地质科学院矿产资源研究所 国土资源部成矿作用与资源评价重点实验室,中国地质科学院矿产资源研究所 国土资源部成矿作用与资源评价重点实验室

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本文受中央级公益性科研院所基本科研业务费专项资金(K1602),国家科技支撑计划课题(2011BAB04B05)和国家自然科学基金(41202056)共同资助


Characteristics of Apatite from 160~140 Ma Cu (Mo) and Mo (W)Deposits in East Qinling
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MLR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Institute of Geology,Chinese Academy of Geological Sciences,MLR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,MLR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences

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    摘要:

    东秦岭地区分布有160~140 Ma斑岩、斑岩矽卡岩型Cu(Mo)和Mo(W)两种不同矿化类型矿床,对两种矿化的成矿岩体中磷灰石进行成分分析,结果显示本次研究的Cu(Mo)和Mo(W)矿床成矿岩体的磷灰石均为岩浆磷灰石,但在主要成分和挥发份上两者具有一定的差异性。相对于Cu(Mo)矿床,Mo(W)矿床成矿岩体的磷灰石具有相对较高的F/Cl比值(分别为81~262和08~25)和MnO含量(分别为:005%~091%,平均为025%和002%~018%,平均为007%),说明Mo(W)矿床成矿岩体的岩浆源区具有较为强烈的沉积物源区特征。随着大地构造位置变化,从华北板块南缘到北秦岭,再到南秦岭,成矿岩体中磷灰石的F/Cl比值和MnO含量逐渐降低,说明岩浆源区中幔源物质成分逐渐增多。与此同时矿化类型也逐渐由Mo(W)矿化转变为Cu(Mo)矿化,这也说明成矿岩体岩浆源区特征对矿化类型具有一定的约束性。此外,Cu(Mo)和Mo(W)矿床成矿岩体中磷灰石具有不同的挥发份含量,而且挥发份类型对不同矿化元素具有选择性。相对于Cu(Mo)矿床,Mo(W)矿床的成矿岩体中磷灰石含有相对较高的F含量(283%~581%,平均为397%),较高的F含量能够提高熔体中羟基含量,增强Mo的配分系数,有利于Mo矿化。Cu(Mo)矿床的成矿岩体中磷灰石含有相对较高的Cl含量(013%~114%,平均为045%),主要与Cu在流体相中主要以氯合物形式存在,且Cu在熔体相和流体相间的分配系数与Cl含量呈正相关关系有关。Cu(Mo)和Mo(W)矿床成矿岩体中磷灰石均含有相似的SO3含量(均为017%),与斑岩型矿床中含矿岩体磷灰石的SO3范围相一致。但是,相对于典型大型、超大型斑岩型铜矿,东秦岭地区晚侏罗世—早白垩世Cu(Mo)矿床的成矿岩体中磷灰石SO3含量略低,相应的成矿岩浆也具有相对较低的氧逸度和S含量,而这可能是造成区域内Cu(Mo)矿化规模较小的原因之一。

    Abstract:

    East Qinling hosts two types of mineralizaiton deposits: 160~140 Ma porphyry and porphyryskarn Cu(Mo) deposits, and Mo(W) deposits. This study carried out composition analysis of the apatite collected from the oreforming rocks. The results show that the apatites in these two deposits are magmatic in origin, although there are some differences between main compositions and volite matters. Apatites from the Mo(W) deposits have higher F/Cl values (81~262) and MnO contents (005%~091%, averaging 025%) than that of the Cu(Mo) deposits (08~25; 002%~018%, averaging 007%), indicating that the magmatic source of the Mo(W) deposits is distinctly characterized by sedimentation provenance. With the change of geotectonic locations from the southern margin of the North China Plate to the North Qinling orogenic belt and the South Qinling orogenic belt, the F/Cl values and MnO contents of apatites from the metallogenic intrusive rocks decrease gradually, suggesting that the mantle material in magmatic source gradually increased. Meanwhile, mineralization types changed from Mo (W) type to Cu (Mo) type, and this change indicates that the characteristics of the magma source have certain restraints on the mineralization types. In addition, the apatites of oreforming rocks in the Cu (Mo) and Mo(W) deposits contain various volatile contents, which have a certain selectivity for mineralization elements. Apatites of the Mo (W) deposits have higher F content (283%~581%, averaging 397%) than the Cu (Mo) deposits (069%~376%, averaging 278%). And higher F contents can not only improve hydroxyl content in the melt but also increase the partition coefficient of Mo, which then promotes Mo mineralization. Apatites of Cu (Mo) deposits have higher Cl content (013%~114%, averaging 045%) than the Mo(W) deposits (0%~004%, averaging 003%), which may be related to the Cu occurrence as chloride compound in the fluid phase, and the coefficient distribution of Cu in the melt and fluid presents positively relationship with Cl content. Apatite contents in the Cu (Mo) and Mo (W) deposits are similar with an average SO3 content of 017% , which is consistent with the SO3 content of apatite from the typical porphyry deposits. However, in comparison with typical large and superlarge porphyry Cu deposits, oreforming rocks of Late JurassicEarly Cretaceous Cu (Mo) deposits in East Qinling have relatively lower SO3 content in apatite; correspondingly, oreforming magma contains lower oxygen fugacity and S content. This may be one of the reasons resulting in smallscale Cu (Mo) mineralization in East Qinling.

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陈雷,闫臻,王宗起,王坤明.2017.东秦岭160~140 Ma Cu(Mo)和Mo(W)矿床磷灰石成分特征[J].地质学报,91(9):1925-1941.
CHEN Lei, YAN Zhen, WANG Zongqi, WANG Kunming.2017. Characteristics of Apatite from 160~140 Ma Cu (Mo) and Mo (W)Deposits in East Qinling[J]. Acta Geologica Sinica,91(9):1925-1941.

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  • 收稿日期:2017-01-12
  • 最后修改日期:2017-03-20
  • 录用日期:2017-04-14
  • 在线发布日期: 2017-09-14
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