Authigenetic K—feldspars and Their Relations to Sn—polymetallic Mineralization in the Dachang Ore Field

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.

Authigenetic K-feldspars and their relations to Sn polymetallic mineralization in the Dachang ore field

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 relations to the bedding: one is distributed along the bedding and the other cuts across the bedding. Sn and sulfide orebodies associated with K-feldspars are mostly characterized by laminated ore structure. Microscopic examinations of K-feldspar-bearing rocks, in conjunction with X-ray diffraction, chemical composition and cathodoluminescence data for K-feldspars, as well as their relations to mineralization, the authors consider that the K-feldspars 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 nesianorogenic movement. It is suggested that more attention should be paid to the effect of authigenic K-feldspars on Sn mineralization. In the meantime the events related to circulating underground hot waters should also be taken into account so as to provide new clues to blind ore prospecting.