CAJ | 학술논문

通过详实的野外调查和室内研究，在西藏吉瓦地区新发现了砂岩型铜矿床，赋矿层位为渐新统日贡拉组，矿床类型为层控矿床。为探讨日贡拉组砂岩的物源特征及其构造背景、查明其含矿物质来源，通过碎屑矿物定量分析、元素地球化学方法及重矿物组合分析等一系列物源分析方法对日贡拉组的物质来源进行了研究。结果显示，研究区主要岩性为岩屑砂岩，岩屑主要成分为酸性火山岩，砂岩结构成熟度低，分选磨圆差。碎屑组分分析表明物源集中在火山弧物源区，地球化学特征为硅质含量高、LREE 富集、HREE 相对亏损、显示 Eu 负异常，均表明物源与酸性火山岩密切相关；日贡拉组砂岩的大地构造背景主要为大陆岛弧，砂岩碎屑来自上地壳长英质源区。重矿物组合以反映物源为中酸性岩浆岩成分的赤褐铁矿＋磁铁矿、锆石、电气石、石榴子石为主，沉积环境为气候干旱、水体较浅的富氧环境。锆石形态特征指示物源距母岩区较近，重矿物的相关性分析也指示了物源与火山岩密切相关。研究区的日贡拉组砂岩与早白垩酸性火山岩微量元素及重矿物的对比表明，碎屑物质源区特点从岩石学特征、地球化学特征及重矿物组合特征上均表现出了亲缘关系，物源成分与火山作用紧密相关，很可能主要来自班公湖怒江洋壳南向俯冲与雅鲁藏布江洋壳北向俯冲双重制约条件下产生于火山弧环境中的早白垩世火山岩。日贡拉组发现了砂岩型铜矿，火山岩提供了成矿物质来源，为寻找同类型的矿床开启思路。
통과상실적야외조사화실내연구，재서장길와지구신발현료사암형동광상，부광층위위점신통일공랍조，광상류형위층공광상。위탐토일공랍조사암적물원특정급기구조배경、사명기함광물질래원，통과쇄설광물정량분석、원소지구화학방법급중광물조합분석등일계렬물원분석방법대일공랍조적물질래원진행료연구。결과현시，연구구주요암성위암설사암，암설주요성분위산성화산암，사암결구성숙도저，분선마원차。쇄설조분분석표명물원집중재화산호물원구，지구화학특정위규질함량고、LREE 부집、HREE 상대우손、현시 Eu 부이상，균표명물원여산성화산암밀절상관；일공랍조사암적대지구조배경주요위대륙도호，사암쇄설래자상지각장영질원구。중광물조합이반영물원위중산성암장암성분적적갈철광＋자철광、고석、전기석、석류자석위주，침적배경위기후간한、수체교천적부양배경。고석형태특정지시물원거모암구교근，중광물적상관성분석야지시료물원여화산암밀절상관。연구구적일공랍조사암여조백성산성화산암미량원소급중광물적대비표명，쇄설물질원구특점종암석학특정、지구화학특정급중광물조합특정상균표현출료친연관계，물원성분여화산작용긴밀상관，흔가능주요래자반공호노강양각남향부충여아로장포강양각북향부충쌍중제약조건하산생우화산호배경중적조백성세화산암。일공랍조발현료사암형동광，화산암제공료성광물질래원，위심조동류형적광상개계사로。
Many detailed field surveys and comprehensive researches have been made to find sandstone copper deposit in Jiwa area,Tibet.Oligocene Rigongla formation sandstoneswere the ore-bearing horizon.The deposit type is strata-bound deposit.Series of provenance analysis technique,for instance,quantitative detrital minerals analysis,elementary geochemical methods and heavy minerals combination analysis,are used to explorethe provenance features and tectonicbackground of Rigongla sandstones.The main lithology is lithic sandstone with a poor sorting and psephicity and low maturation of texture.The detrital compositions hintthe main setting background of provenance is continental island arc,the geochemical characteristics are high value of siliceous,enrich in LREE,relatively depleted in HREE,and negative Eu anomalies.They all show that the provenance is closely related to acid volcanic rocks,the main setting background of Rigongla formation sandstone is continental island arc,the lithic sandstones came from felsic part of upper crust,heavy mineral combinations mainlyarehematite-limonite and magnetite,zircon,tourmaline,garnet,which were related to intermediate-acid magmatic rocks. Sandstone was deposited in dry,restricted shallow water and oxidizing environment.The morphological characteristics of zircons indicate that provenance is close to mother rocks.The correlation analysis of heavy minerals also shows that provenance is closely related to volcanic rocks.Comparingto acid volcanic rocks of the lower stratum and early cretaceous volcanic rocks in this area,trace elements and heavy mineral sreveal that the characteristics of detrital material source area were showed genetic relationship from petrology characteristics, geochemical characteristics and heavy mineral assemblages. The provenance of fragments were closely related to volcanic activities,may come from the acid volcanic rocks of early Cretaceous associated with the southward subduction of the Bangong Co-Nujiang oceanic crust and northward subduction of the Yalung Zangbo oceanic crust.Sandstone copper deposits was found in Rigongla Formation,volcanic rock provides the source of ore-forming materials.