The Geological Structure and Metasomatic and Hidden Mineralogical Zonation of the Kyzyk-Chadr Porphyry Copper Deposit, Republic of Tuva

摘要

The altered rocks of the Kyzyk-Chadr deposit are mostly composed of quartz and dioctahedral K-micas of the muscovite-phengite series, which are dominant in almost in all zones of a metasomatic aureole. The assemblages of albite with chlorite and epidote are typical only of the peripheral parts of this aureole characterized by propylitic alteration. The central and deep areas of the aureole exhibit quartz-feldspar alteration. To reveal the hidden mineralogical zonation of the deposit, we studied the petrography of metasomatites and used the results of X-ray diffractometry (XRD) and IR spectroscopy of micas from the mineralized quartz-sericite metasomatites. The elements of hidden mineralogical zonation, which depends on the variations in the amount of phengite and muscovite of light mica metasomatites, are identified on the basis of XRD and IR spectroscopy. Phengite is a dominant component of the central and deep parts of the ore-metasomatic aureole of the deposit, whereas the amount of the muscovite component gradually increases toward the flanks and the upper parts. This trend is correlated with a general direction of mineralogical ore-metasomatic zonation and can probably be explained by the change in P-T conditions in a volume of a porphyry copper ore-magmatic center. The phengite/muscovite ratio (an indicator of hidden mineralogical zonation) can be used for searching for and estimation of porphyry copper deposits as an objective criterion during the correlation between known and forecasted ore bodies.