Breccia Identification as Ore Vectoring in Seruyung Gold Mine, Indonesia

Mineral system understanding

Mr. Ahmad Khoirul Basyar

J Resorces Nusantara

Seruyung deposit which is located at North Kalimantan recognized as the one of high sulfidation epithermal deposit in Indonesia. The mineralization occurred in hydrothermal breccia with diatreme breccia and intrusive andesite as a host rock. In terms of alteration, typical of high sulfidation epithermal deposit observed with vuggy quartz as the core of mineralization degrading outward to quartz-alunite and quartz-pyrophylite as the silica-rich advance argillic alteration, quartz-dickite/kaolinite as clay-rich advance argillic alteration, and illite-smecite as argillic alteration. Furthermore, breccia identification is a fundamental key to define where gold mineralization occurred by identifying the breccia genetics and its relationship.

Breccia identification on Seruyung was conducted by core and fieldwork data acquisition which emphasizing on breccia organization consisting matrix and cement content and clast organization. The breccia matrix and cement characteristic divided into quartz±clay±alunite±sulfide mineral, quartz±clay±alunite±FeOx mineral, clay±sulfide, and clay±FeOx mineral. Clast organization observed varies from jigsaw fit to chaotic textures with monomict and polymict clast. Mineralized breccia commonly occurred in quartz-alunite-hematite, clay-sulfide, and clay-FeOx matrix and cement. Sulfide and FeOx veinlets are believed as the gold bearing mineralization in clay-sulfide and clay-FeOx cement.

The cross-cutting relationship of breccia is determined by observing contact and clast composition. The understanding of breccia relationship is important to determine the breccia sequence and modelling the spatial and breccia body continuity which play a key role to ore vectoring as exploration target generation in Seruyung Gold Mine.

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