云南澜沧老厂地洼型银铅矿床的地球化学特征及成因

GEOCHEMICAL FEATURES AND GENESIS OF THE LAOCHANG DIWA-TYPE SILVER-LEAD ORE DEPOSIT IN LANGCHANG, YUNNAN, CHINA

澜沧老厂地洼型银铅矿床的主要成矿物质铅锌银铜主要来自地洼期隐伏岩体,其次是来自地槽构造层(围岩),其中火山岩仅可能提供部分锌;成矿时间为87～50Ma,形成温度为200～350℃;成矿热液为以金铜系列初始岩浆水为主,伴有大气降水掺加;铜与铅锌银不关联。该矿床不是地槽阶段海西-印支期的火山沉积矿床或远成中低温热液矿床,而是地洼阶段燕山晚期至喜山早期形成的与地洼隐伏岩体有关的中偏高温多因复成矿床。

Ore—forming materials of the Laochang diwa-type silver—lead ore deposit is derived firstly from the blind rock bodies formed in the diwa period, and secondly from the geosynclinal structural layer (host rocks). Among these rocks, volcanic rocks only provide a part of zine. The metellogenic age and temperature are 87-50 Ma and 200-350℃ , respectively. The ore—forming flnid is dominated by juvenile magmatic water, mixed by atmospheric water. Copper has nothing to do with Pb, Zn and Ag. This deposit is a middle-high temperature polygenetic compound one, pertinent to diwa-period blind rock bodies, formed in the period from the late Yanshanian to the early Himalayanian, rather than a Hercynian to Indosinian volcano-sedimentary one or middle-low temperature telethermal one.