加里曼丹岛Lamandau铜金多金属矿床地球化学研究及其地质意义

Kalimantan Island is the largest island in Southeast Asia, which is located at the southeastern margin of the Eurasia plate. The tectonic setting of Kalimantan Island belongs to the junction of western Pacific-Tethys tectonic regime. The Mesozoic- Cenozoic magmatic rocks and metal deposits are widely developed in this Island, including Au, Cu-Au polymetallic deposits and others. But now the research works on these magmatic rocks and metal deposits are relatively defective, and the formation mechanism of these deposits are still controversial. This project will focus on the Lamandau Cu-Au polymetallic deposit and the host arc magmatic rocks in the Sanda block of the southeastern Kalimantan Island, and carry out systemetic geological-geochemical researches. The applicants have collected a mount of arc magmatic rocks and ore samples during the previous field works. The project will carry out further field works, systemetic elemental, isotopic geochemical, geochronologic researches and other necessary analyses, in order to accurately constraint the forming ages and formation mechanism of this deposit and the host arc magmatic rocks, and also propose reasonable metallogenic model. The researches on this deposit can propose scientific suggestions for further prospecting in Kalimantan Island, and also provide evidences for the evolution of New Tethys tectonic regime and the expansion process of the South China Sea.

加里曼丹岛是东南亚最大的一个岛屿，位于欧亚板块的东南缘。该岛大地构造位置属于西太平洋-特提斯构造域交汇带。该岛内中-新生代岩浆岩及金属矿床十分发育，包括金和铜金多金属矿床等。但是现在对于这些岩浆岩及金属矿床的研究相对薄弱，这些矿床的成因机制还存在很大争议。本申请选取加里曼丹岛西南部巽他陆块的Lamandau铜金多金属矿床和成矿相关的岛弧岩浆岩作为研究对象，开展地质-地球化学综合研究。申请人在前期野外勘查工作中已经到该矿区采集到了大量的岛弧岩浆岩和矿石样品。本项目将通过进一步的野外勘查工作，系统的元素、同位素地球化学及年代学等先进的分析技术，精确限定Lamandau矿床及与成矿相关岛弧岩浆岩的形成时限、成因机制，建立合理的成矿模式。本研究将为区域找矿提供科学依据，也为新特提斯构造域演化和南海扩张过程提供相关依据。

加里曼丹岛是婆罗洲印尼属地的称呼。本项目对加里曼丹岛西南部Lamandau地区岛弧岩浆岩、沉积岩及多金属矿床进行研究。Lamandau地区辉石闪长玢岩与铁铜金多金属矿床的形成密切相关。全岩Sr-Nd同位素分析结果表明该区辉石闪长玢岩具有正的εNd(t)值和较低的(87Sr/86Sr)i比值。该区岩石具有相对年轻的单阶段Nd模式年龄，锆石Hf同位素组成与高温橄榄岩接近，表明岩浆源区为新生的年轻岩石圈地幔。辉石闪长玢岩中锆石具有较低的εHf(t)值，出现Nd-Hf同位素解耦现象，是受“石榴子石效应”影响的结果。岩石的Nd-Hf模式年龄属于新元古代，表明岩浆源区中可能有俯冲再循环的大洋沉积物加入。婆罗洲西南部微板块(SW Borneo)是该岛最古老的大陆碎片，来自冈瓦纳大陆。采自该区域中发育的吉打邦杂岩体砂岩中113颗碎屑锆石U-Pb定年结果表明其年龄分布为3298~78Ma，年龄谱呈现多峰态分布特征。最年轻的碎屑锆石年龄为78Ma，表明该区域砂岩的最大沉积时代应该为晚白垩世坎帕期(Campanian)。物源分析表明二叠纪-晚白垩世碎屑锆石主要来自附近的Schwaner山脉以及东南亚锡矿带花岗岩。太古代-石炭纪碎屑锆石源区为澳大利亚西北部和中部造山带和克拉通等。婆罗洲西南部微板块在古生代位于澳大利亚西北缘。该微板块在早侏罗世发生裂解之后向北运动，并在早白垩世加入到巽他大陆。Lamandau地区Ruwai Fe-Zn-Pb-Ag矿床中Sukadana花岗闪长岩中的锆石定年结果为95.0±0.7Ma，矽卡岩石榴子石U-Pb定年结果为94.7±1.5Ma，表明该区矽卡岩矿化最早形成于晚白垩世早期，与区内花岗闪长岩体的侵入密切相关。该区锆石Hf同位素与全岩Nd同位素呈耦合关系，具有相对年轻的二阶段Hf模式年龄，表明岩体可能由年轻的新生地壳部分熔融形成。Sukadana花岗闪长岩具有类似岛弧岩浆岩的特征，形成于后碰撞环境。Ruwai矿床形成温度为中低温环境，成矿流体主要为含硫流体。