甘肃白银厂小铁山韧性剪切带体积亏损与成分变异

白银厂矿田分布有多条韧性剪切带,在空间上与矿体关系密切.对小铁山韧性剪切带岩石地球化学研究表明,在韧性剪切变质变形过程中,岩石中的元素发生不同程度的变异,主要表现为活动性较小的高场强元素有规律的富集,活动元素有带入(富集)或带出(亏损)的变化规律.本文认为:稳定元素的富集与剪切带的体积亏损(初糜岩27%,糜棱岩35%)有关,活动元素的变异主要与流体作用有关.剪切带中大量的SiO2流失和高的流体/岩石比(初糜岩95～474;糜棱岩129～646)表明,剪切带中的渗透流体对成矿作用具有重要影响.

The component variation and volume loss of Xiaotieshan Shear Ductile Zone in Baiyin Ore Field, Gansu Province

The ductile shear zones developed in Baiyin Mine are closely related with the ore bodies in spatial distribution. The results of study on the petrological geochemistry of the Xiaotieshan ductile zones show that syn-deformational fluid-rock interaction had produced substantial component variance of the rocks within ductile zone and that the volume loss (mylonitized rhyorite and mylonite up to 27% and 35% respectively) and flow fluids within the ductile zones cause the deformed rocks to enrich HFSE inactive elements and to deplete or enrich active elements. The loss of a great amount of SiO2 (mylonitized rhyorite and mylonite up to 23.7% and 32.3% respectively) and the high fluid/rock ratios (mylonitized rhyorite and mylonite up to 95-474 and 129-646 respectively) indicates that the fluid flow within the ductile zones had played a very important role in the mineralization.