Sn-polymetallic ores at Dachang,Guangxi Autonomous Region,China,are hosted in Middle-Upper Devonian reef limestones,siliceous rocks,banded and lenticular limestones,etc.Two types of orebodies can be distinguished according to their telations to the bedding:one is distributed along the bedding and the.other cuts across the bedding.Sn and sulfide orebodies associated with K-feldspare are mostly characterized by laminated ore structure. Microscopic examinations of K-feldspar-bearing rocks,in conjunction with X-ray diffraction,chemical composiion and cathodoluminescence data for K-feldspars,as well as their telations to mineralization,the authors consider that the K-feldspare are of authigenic origin,subordinate to the epigenetic stage of diagenesis,They resulted from the reaction of mixed,deep-seated,circulating underground hot waters rich in K,Al and Si with argillaceous carbonates during the Indo nesian orogenic movement.It is suggested more attention should be paid to the effect of authigenic K-feldspars on Sn mineralization.In the meantime the event related to circulating underground hot waters should also be taken into account so as to provide new clues to blind ore prospecting.
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