西藏嘎拉勒铜金矿床地质特征及矽卡岩矿物学特征研究

嘎拉勒铜金矿床位于班公湖-怒江缝合带西段,是该带上新近发现的十分重要的矽卡岩(斑岩)型铜金矿床,其金资源量已达大型以上规模。矿区内出露地层有白垩系朗久组及捷嘎组,并发育大量燕山期中酸性侵入岩。矿体主要产于灰白色花岗闪长岩与白云岩或白云质大理岩的接触带矽卡岩内。矽卡岩主要呈层状、似层状、港湾状及不规则状等产出;矽卡岩矿物主要为橄榄石、蛇纹石、辉石、金云母、透闪石、绿帘石、水镁石等;靠近内接触带可见石榴子石;金属矿物主要有磁铁矿、自然金、黄铜矿、斑铜矿、辉铜矿、辉钼矿等。电子探针分析表明,矿区内矽卡岩矿物中的橄榄石主要为镁橄榄石,辉石主要为透辉石,云母主要为金云母,由此构成的矽卡岩矿物组合为典型的镁质矽卡岩;与之伴生的钙质矽卡岩矿物石榴子石主要为钙铁榴石。矿区中的矽卡岩在空间上具有较好的分带性,其表现为从内接触带至外接触带经历了镁橄榄石-透辉石相至金云母-透闪石相的渐变过渡演化,表明矿区矽卡岩具有从高温至低温的矿物组合演化序列;与矽卡岩分带相伴随的矿化分带,表现为深部的铜(钼)矿化过渡到浅部的铜金矿化。矿区最新勘查成果显示,在深部已发现少量斑岩型矿化,显示存在统一的矽卡岩-斑岩成矿系统的可能性,深部找矿潜力较大。

Geological and skarn mineral characteristics of Galale Cu-Au deposit in Tibet

Located in the west part of Bangong Lake-Nujiang River suture zone, the Galale copper-gold deposit is a very important skarn (porphyry) copper-gold deposit discovered in recent years. Its gold reserves have reached a large size deposit. The exposed strata in the ore district is Cretaceous Longjiu Formation and Jiega Formation, with the development of a large number of Yanshanian acid intrusive rocks. The ore bodies mainly occur in grayish white granodiorite and dolomite or within the contact zone of dolomitic marble. The skarns are mainly of layered, quasi-lamellar, embayed and irregular forms, and the skarn minerals mainly include olivine, serpentine, pyroxene, phlogopite, tremolite, garnet, epidote and brucite; near the inner contact zone there exists garnet, and the metallic minerals are mainly magnetite, natural gold, chalcopyrite, bornite, chalcocite, and molybde-nite. Electron microprobe analysis shows that the skarn mineral is mainly forsterite olivine, pyroxene is mainly diopside, mica is mainly phlogopite, and the skarn mineral assemblage is a typical magmatic skarn associated with calcareous skarn mineral of andradite. Skarn in the ore district shows obvious spatial zonation, and from the inner contact zone outwards it assumes the gradual transition from the forsterite-diopside facies to the phlogopite-tremolite facies, suggesting that the mineral assemblages of the skarn in the ore district has a evolutionary series from high temperature to low temperature. In addition, the skarn zoning is associated with mineralization zoning, manifested as the transition from the deep copper (molybdenum) mineralization to the shallow copper-gold mineralization. The latest exploration results in the ore district revealed a small amount of porphyry mineralization in the depth, suggesting the possible existence of a unified skarn-porphyry mineralization system and a favorable prospecting potential in the depth.