MECHANISMS OF Cu-Au ENRICHMENT IN ORE MYLONITES OF THE HONGTOUSHAN MASSIVE SULPHIDE DEPOSIT, LIAONING, NE CHINA
MECHANISMS OF Cu-Au ENRICHMENT IN ORE MYLONITES OF THE HONGTOUSHAN MASSIVE SULPHIDE DEPOSIT, LIAONING, NE CHINA
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作者：
GU Lian-xing
辽宁省红头山太古代铜锌块状硫化物矿床成矿后变质作用属上角闪岩相，具有三期变形作用。矿床矿石矿物以黄铁矿、磁黄铁矿、黄铜矿、闪锌矿为主。主要块状硫化物矿体内发现糜棱岩型矿芽30余处。它们中的大多数与块状硫化物矿层的走向平行或近平行，只有少数在紧邻硫化物矿体的变质岩中发育。矿芽中几乎所有的硫化物矿物都受到了强烈的韧性剪切的影响。黄铁矿具有碎裂流特征，而磁黄铁矿、黄铜矿和闪锌矿则表现出较强的可塑性。矿石糜棱岩中 Cu、Au 和 Ag 的平均含量分别为 11.00 wt%、1.74 g/t 和 235.2 g/t。与块状硫化物矿石相比，矿石糜棱岩对这些元素表现出显着的富集，富集系数分别为5.3、5.0和4.6。这些成矿金属的高富集基本上是由于晚期流体在矿石糜棱岩上的叠印所致。铅同位素组成表明矿石糜棱岩中的金属部分来源于原块状矿石，部分来自块状矿石之外。延性剪切和流体叠印都发生在逆变质过程中。
The post metallogenic metamorphism of Hongtoushan Archean Cu-Zn massive sulphide deposit, Liaoning Province of NE China, belongs to upper amphibolite facies with three phases of deformations. Ore minerals in the deposit are dominated by pyrite, pyrrhotite, chalcopyrite and sphalerite. There are more than 30 mylonite-type oreshoots found inside the main massive sulphide orebodies. Most of them run parallel or sub-parallel to the strike of the massive sulphide ore layers with only a few being developed in metamorphic rocks in the immediate vicinity of the sulphide orebodies. Almost all the sulphide minerals in the oreshoots have been affected by intense ductile shearing. Pyrite is characterized by cataclastic flow, while pyrrhotite, chalcopyrite and sphalerite exhibit strong plasticity. Cu, Au and Ag in ore mylonite are averaged in 11.00 wt%, 1.74 g/t and 235.2 g/t respectively. Compared to the massive sulphide ores, ore mylonites show remarkable enrichment of these elements with enrichment coefficients of 5.3, 5.0 and 4.6 respectively. The high enrichment of these ore-forming metals is basically due to the overprinting of late-stage fluids on ore mylonites. The composition of lead isotopes suggests that the metals in the ore mylonites were derived partly from the original massive ores, and partly from outside the massive ores. Both ductile shearing and fluid overprinting took place during retrograde metamorphism.