辽吉古元古代造山带小女寨变辉长闪长岩的成因及其对钴镍富集成矿作用的制约  

The petrogenesis of the Xiaonvzhai metamorphic gabbro-diorite in the Liaoji Paleoproterozoic orogenic belt and its constraints on Co-Ni enrichment

作　　者：王娜 王丹[1] 刘福来[1] 王舫[1] 马双 魏巍 孙立秋[2] WANG Na;WANG Dan;LIU FuLai;WANG Fang;MA Shuang;WEI Wei;SUN LiQiu(Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;No.5 Geological Party Limited Liability Company of Liaoning Province,Dashiqiao 115100,China)

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]辽宁省第五地质大队有限责任公司,大石桥115100

出　　处：《岩石学报》2024年第10期3131-3159,共29页Acta Petrologica Sinica

基　　金：国家重点研发计划项目(2022YFC2903502);国家自然科学基金项目(92062214、42072221);中国地质科学院基本科研业务费(J2302、JB2304);中国地质调查项目(DD20242528)联合资助.

摘　　要：辽吉造山带是华北克拉通一条重要的古元古代造山带,该造山带在古元古代盆地拉张时期接受了大量陆壳沉积物,这些沉积物质组成和多期的岩浆-变质事件为辽吉造山带富集成矿提供了有利的条件。辽吉造山带内除了发育与千枚岩-片岩相伴生的沉积岩-变沉积岩容矿型铜钴矿床,还发育与基性岩相伴生的岩浆型铜镍钴矿床。然而,对于岩浆型Co-Ni矿的富集成矿模式及钴镍富集规律的研究较为薄弱。本文选取辽河群小女寨变辉长闪长岩开展了岩相学、矿物化学、锆石U-Pb年代学、全岩地球化学及硫化物硫同位素的研究,以进一步理清辽河群Co-Ni成矿机制及物质来源。变辉长闪长岩具有变化的SiO_(2)(26.1%~57.3%)、MgO(2.90%~25.0%)、CaO(3.17%~10.7%)和FeO^(T)(6.43%~38.94%)含量,属于钙碱性系列。具有轻稀土富集和重稀土平坦的稀土配分模式,相对亏损高场强元素(如Ta、Nb、Ti)。锆石U-Pb同位素分析获得的变辉长闪长岩变质原岩的形成时代为~2.17Ga。锆石εHf(t)值的变化范围为-1.3~+5.0,指示基性岩的岩浆源区来自富集地幔的部分熔融,可能与岩石圈伸展作用相关。变辉长闪长岩中钴镍主要赋存于辉砷钴矿(Co:14.8%~31.3%;Ni:2.92%~14.2%)和镍黄铁矿(Co:5.70%~8.53%;Ni:27.3%~34.0%)中,富Co-Ni的矿物与石英、绿帘石等矿物共生,指示其成矿作用可能与晚期热液有关。小女寨变辉长闪长岩硫化物的S同位素分馏程度较弱(+4.5‰~+5.5‰),表明成矿物质来源均一。且具有比地幔更重的δ^(34) S值,表明硫化物的S可能来源于大陆地壳。小女寨地区2个钻孔岩心样品均具有较高的Ni(0.09%~0.94%)、Co(0.01%~0.13%)和Cu(0.02%~0.79%)品位,表明辽吉造山带古元古代变基性岩具有Cu-Co-Ni的成矿潜力。The Liaoji orogenic belt is a major Paleoproterozoic orogenic zone in the North China Craton.During the extension of the Paleoproterozoic basin,the Liaoji orogenic belt accumulated substantial continental sediments.These sediments,combined with multi-stage magmatic and metamorphic events,provided favorable conditions for mineral enrichment and formation of the deposits.Cu-Co deposits have been found in association with metamorphic sedimentary rocks,particularly in phyllite-schist.In addition,magmatic Co-Ni deposits associated with mafic rocks have been reported in the region.However,the enrichment mechanisms and metallogenic models for the magmatic Co-Ni deposits remain unclear.In this study,we investigated the petrography,mineral chemistry,zircon U-Pb geochronology,whole-rock geochemistry,and sulfide-sulfur isotopes of the Xiaonvzhai metamorphic gabbro-diorite from the Liaohe Group to further understand the Co-Ni metallogenic mechanisms and the source of the Co-Ni in the Liaohe Group.The studied samples of the metamorphic gabbro-diorite have variable compositions,i.e.,SiO_(2)(26.1%to 57.3%),MgO(2.90%to 25.0%),CaO(3.17%to 10.7%)and FeO^(T)(6.43%to 38.94%),indicating that they belong to the calc-alkaline series.They are characterized by slightly enriched light rare earth elements and flat heavy rare earth patterns,with relatively negative anomalies in high field strength elements(such as Ta,Nb,and Ti).Zircon U-Pb isotopic dating defined the age of the metamorphic gabbro-diorite to be approximately 2.17Ga,with zirconεHf(t)values of-1.3~+5.0,suggesting that the mafic magma source of the pluton was derived from partial melting of the enriched lithospheric mantle that would likely be related to the lithospheric extension.The Co-Ni contents in the metamorphic gabbro-diorite are mainly from cobaltite(Co:14.8%to 31.3%;Ni:2.92%to 14.2%)and pentlandite(Co:5.70%to 8.53%;Ni:27.3%to 34.0%).These Co-Ni-rich minerals coexist with quartz,epidote and other minerals,suggesting that the mineralization may be associated with late-s

关 键 词：辽吉造山带 辽河群 变辉长闪长岩 古元古代 钴镍成矿 

分 类 号：P588.122[天文地球—岩石学] P597.3[天文地球—地质学] P618.62P618.63