摘要
黄羊山矿床是最近在新疆发现的一个超大型晶质石墨矿床,预测晶质石墨矿物量至少为72.64 Mt。该矿床赋存于花岗岩内,90%的石墨呈球粒状构造,球粒直径最高达20 cm,世界罕见。通过钻孔岩芯编录、探槽编录、镜下观察和锆石U-Pb定年,研究了该矿床矿化情况、矿物组合和成岩年代,探讨了矿床成因。研究表明,黄羊山石墨矿床成岩于(306±4)Ma,属晚石炭世。石墨球粒和基质的岩性相同,皆为碱长花岗岩,只是石墨球粒内较为富集黑云母、角闪石和单斜辉石。与石墨伴生的金属矿物主要为磁黄铁矿、黄铜矿、钛铁矿和赤铁矿。由于石墨的强还原性,这些金属矿物多分布于石墨球粒内,形成典型的环带结构。石墨矿化可分为岩浆热液期和热液叠加期2期,前者是主成矿期,形成球粒状和浸染状构造石墨,后者形成脉状构造石墨。石墨晶体呈片状和胶状结构,片状石墨横截面呈针状,定向性明显。石墨矿石的全岩碳同位素呈负低值,表明构成石墨的碳来自地层有机物。岩浆在上侵过程中同化混染了地层有机物,在岩浆演化晚期熔体相与流体相分离时,碳质溶入流体相中,当温度和压力降低时石墨从岩浆热液中沉淀成矿。中粒钠铁闪石花岗岩、细粒黑云母花岗岩和中粒黑云母花岗岩中皆含石墨球粒,黄羊山岩体仍具有巨大找矿潜力。
The Huangyangshan deposit is a superlarge crystalline graphite deposit recently discovered in Xinjiang.The reserves of crystalline graphite in the deposit are estimated at least 72.64 Mt.The deposit is hosted in granite,and 90%of graphite is of spherulitic structure.The longest diameter of the spherulite can reach 20 cm.It is extremely rare in the world.Through drill core logging,prospecting trench logging and petrographic and zircon U-Pb geochronologic studies,the authors investigated mineralization,mineral assemblage and diagenetic age of the deposit,and discussed its ore genesis.The results reveal that the diagenetic age of the deposit is(306±4)Ma,which is Late Carboniferous.Graphite spherulite and matrix have the same lithology of alkali-feldspar granite.However,biotite,hornblende and clinopyroxene are relatively more concentrated in the spherulite.Metallic minerals associated with graphite are pyrrhotite,chalcopyrite,ilmenite and hematite.Due to strong reducibility of graphite,these metallic minerals are mainly distributed within graphite spherulite,forming typical zoning texture.Graphitization could be divided into two periods,namely magmatic hydrothermal period and hydrothermal superimposition period.The former was the principal oreforming period,producing spherulitic and disseminated graphite,while the latter produced vein graphite.Crystals of graphite are of flaky and colloform texture.The flaky graphite is in acicular form along the section and has preferred orientations.Graphite ores have low negative bulk-rock carbon isotopic composition,which implies that the carbon consisting of graphite was derived from organic matters in strata.Magma assimilated organic matters in strata during its ascending.At the late stage of magma evolution,with the separation of the melt and liquid phase,carbonaceous matters were incorporated into the liquid phase.When the temperature and pressure decreased,carbon precipitated from the magmatic hydrothermal to form graphite.Medium-grained arfvedsonite granite and fine and medium grained biotite granite contain graphite spherulites,and hence Huangyangshan pluton has considerable ore-prospecting potential.
作者
艾江
吕新彪
李作武
吴亚伦
AI Jiang;Lü Xinbiao;LI Zuowu;WU Yalun(China University of Geosciences,Wuhan 430074,Hubei,China;Xinjiang General Party,China National Geological Exploration Center of Building Materials Industry,Urumqi 830092,Xinjiang,China)
出处
《中国地质》
CAS
CSCD
北大核心
2020年第2期334-347,共14页
Geology in China
基金
中国地质调查局项目“新疆奇台县黄羊山一带石墨矿调查评价”(DD20160058-01)资助。
关键词
石墨矿床
矿床地质
矿床成因
锆石U-PB定年
地质调查工程
黄羊山
新疆
graphite deposit
deposit geology
ore genesis
zircon U-Pb geochronology
geological survey engineering
Huangyangshan
Xinjiang
