冈底斯东段泽当大型钨铜钼矿新发现及走滑型陆缘成矿新认识

冈底斯成矿带以斑岩型铜矿(伴生钼矿)为主体,通常作为"挤压型"陆缘岩浆弧—"碰撞裂谷带"斑岩成矿的典型代表而被广泛关注,但层矽卡岩型钨铜钼矿和斑岩型独立钼矿的勘查和研究却未能引起足够的重视,尤其是层矽卡岩型白钨矿的发现,填补了区带矿种的空白;在雅鲁藏布江缝合带边部发现的隐伏斑岩型钼矿,突破了"挤压型"陆缘成矿认识的传统误区。中国冶金地质总局新近发现的冈底斯东段则当钨铜钼矿,既是一处大型钨铜钼矿详查开发基地,又是一组统一于陆缘走滑断裂构造成矿体制作用的钨、铜、钼矿床组合,称为"泽当矿田"。在NWW向雅鲁藏布江缝合带陆缘走滑断裂作用下,早期(68～40.3Ma)拉分型转换构造——NEE向剥离断层,控制了层矽卡岩型钨铜钼矿的形成;在NEE向冲木达陆缘走滑断裂作用下,晚期(30.26～23.62Ma)推闭型转换构造——NWW向逆冲断层,控制了隐伏斑岩型钼矿的形成。层矽卡岩型矿床形成和改造于68～66Ma和57～40.3Ma,叠加富集于斑岩型矿床的形成阶段——30.26～23.62Ma。

Discovery of Large Zedang Tungsten-Copper-Molybdenum Orefield, Eastern Gangdese Arc, and New Understanding on Strike-Slip Type Epicontinental Mineralization

Porphyry-type copper ore (associated with molybdenum ore) is the dominant ore in Gangdese metallogenic belt, which is widely concerned as the typical of exclusion epicontinental magmatic arc-collision rift belt porphyry mineralization. However, it has not been attached importance to the exploring and researches about skarn-type tungsten-copper-molybdenum ore and porphyry-type independent molybdenum. Especially the discovery of ledge skarn type scheelite ore fills in the mineral gaps in the ore field;and the discovery of concealed porphyry-type molybdenum minerals in the border of Yarlung Zangbo suture zone breaks traditional erroneous zone of the understanding of exclusion epicontinental mineralization. Tungsten-copper-molybdenum ore, discovered by our bureau in Zedang orefield, eastern Gangdese Arc, is not only a large base to explore and exploit tungsten-copper-molybdenum deposits, but also a group of tungsten-copper-molybdenum deposits (short for Zedang orefield) affected by epicontinental strike slip rift mineralization system. At the early stage(68～40.3Ma), under the epicontinental strike slip rift effects of NWW trending Yarlung Zangbo suture zone, the formation of skarn-type tungsten-copper-molybdenum mineralization was controlled by rift-fault transfer zone--NEE trending striping faultage;while at the later stage(30.26～23.62 Ma), under the epicontinental strike-slip rift effects of NEE trending Chongmuda, the formation of concealed porphyry-type molybdenum minerals was controlled by push-close transfer zone--NWW trending thrust faultage. The formation and change of skarn-type deposit completed in 86～68 Ma and 57～40.3 Ma, respectively, and they enriched in porphyry-type deposit in 30.26～23.62 Ma.