壳型剪切带中金矿预测参数

本文设想把华北陆台北缘前寒武纪变质岩区韧性剪切变形-变质带中金矿成矿作用做为区域变质作用-构造作用-岩浆作用旋回中的一部分。这类金矿主要形成在这一旋回的晚期,变质地质体被抬升的阶段,并就位于低温韧-脆性变形变质带中,属于各种内动力地质作用的综合产物。分析韧性剪切变形-变质带(DDMZ)内金矿成矿过程中的这种多因素、多阶段的各种信息,我们提出如下参数:区域性参数富铁质变质岩石组合和壳型剪切带;最佳区段参数—低温韧-脆性变形-变质带和弱碱性钾质花岗岩;金矿化带参数—岩石-流体交代带。其目的是明确找矿目标,提高金矿预测有效性。

PARAMETERS FOR INFERRING GOLD DEPOSITS IN CRUSTAL SHEAR ZONE

It is proposed that gold mineralization occuring within ductile shear deformation- metamorphism zone(DDMZ)is a part of regional metamorphism-tectonism-magmatism cycle by the paper. According to the relationship between DDMZ action and metamorphism, the DDMZ can be divided into three basic types: high-pressure type related with subduction or nappe, belonging to high-pressure metamorphism; low-pressure type related with extension, being of low-pressure metamorphism; retrograde metamorphic type occurring in the late stage of a metamorphic cycle or overprinted by another metamorphic event. Gold deposits often occured in the zone of the last type. When the metamorphosed crust was uplifted at the later stage of the metamorphic cycle, gold deposits formed in the lower temperature ductile-brittle deformation- metamorphic zone as a result of fluid-rock reaction. To define the target looking for gold deposits and improve the degree of inferring accuracy the paper, based on the analysing of various information about complicated gold mineralization, presents the following parameters: regional parameters, including Fe-rich metamorphic rock association and crustal DDMZ; the favourable section parameters, including low-temperature ductile- brittle deformation-metamorphic zone and weakly basic potassic granite bodies; gold mineralization zone parameters, namely, fluid-rock alteration zone.