河南省老湾金矿韧性剪切带特征及成矿机制探讨

Discussion on the Characteristics and Metallogenic Mechanism of the Ductile Shear Zone in Laowan Gold Deposit,Henan Province

老湾韧性剪切变质带是北秦岭古生代褶皱带与南秦岭印支褶皱带分界构造的一部分,呈NWW向展布,分为四个主应变带和两个岩片带。带内岩性分布以基性岩浆岩为主,兼有部分变质岩块体、酸性岩浆岩体和岩脉等。金矿化严格受韧性剪切变质带控制,主要集中分布在RF4强应变域中心及两侧的Ⅱ岩片区,辉绿一辉长岩为金的矿源层,后期老湾黑云母花岗岩对含金热流体起着成分改造和加强循环的作用。矿床成矿机制复杂,泥盆纪末,南北大陆发生碰撞,基性岩浆侵入,部分Au带入岩浆→印支期,发生强烈韧性剪切变形变质,Au元素活化运移,向强应变部位富集→燕山期,老湾花岗岩岩浆的热加入,Au进一步在剪切强应变带聚积成矿。

The Laowan ductile shear metamorphic zone is a part of the boundary structure between the North Qinling Paleozoic fold zone and the South Qinling Indosinian fold zone,distributed in an NWW direction and divided into four main strain zones and two strong foliated metamorphic zones.The lithology distribution within the zone is mainly composed of basic magmatic rocks,with some metamorphic rock blocks,acidic magmatic rocks,and rock veins.The gold mineralization is strictly controlled by the ductile shear metamorphic zone,mainly concentrated in the center of the RF4 strong strain domain and the II strong schistosity zone on both sides.The diabase gabbro is the source layer of gold,and the later Laowan biotite granite plays a role in compositional transformation and strengthening circulation of gold bearing thermal fluids.The mineralization mechanism is complex.At the end of the Devonian,there was a collision between the northern and southern continents,with basic magma intrusion.Some Au was brought into the magma→Indosinian period,and strong ductile shear deformation and metamorphism occurred.Au elements were activated and migrated,enriched towards strong strain areas→Yanshan period.The addition of heat from the Laowan granite magma further led to the accumulation and mineralization of Au in the shear strong strain zone.