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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 66 (1982)

Issue: 7. (July)

First Page: 981

Last Page: 981

Title: Rock-Multielement-Geochemistry at Copper-Gold Anomaly in Kaputusan (Bacan Island), Moluccas, Indonesia: ABSTRACT

Author(s): H. Pudjowalujo, D. Bering

Article Type: Meeting abstract

Abstract:

Geological reconnaissance and mineral prospecting on Bacan Island (Moluccas, Indonesia) by the Directorate of Mineral Resources of the Republic of Indonesia, from 1977 to 1979, resulted in the discovery of a copper-gold anomaly situated 7.5 mi (12 km) north of Kaputusan village. Technical cooperation with the Bundesanstalt fur Geowissenschaften and Rohstoffe of the Federal Republic of Germany, from 1980 to 1981, detailed the prospect with geochemical analyses and geologic mapping.

The interpretation of a geochemical pattern, based on analyses of 32 elements in 149 rock samples from test pits in the anomalous area, indicated porphyry copper mineralization. In the center of the anomaly, enrichment of Au, Mo, Bi, Zr, Rb, and K2O was detected, with surrounding halos of Pb, Zn, Sr, MnO, Fe2O3 and trace elements. Ratios of Rb/Sr and K2O/Na2O provided further evidence.

SiO2 and SO3 are relatively rich in the southern part of the anomaly, confirming a previously mapped quartz sericite alteration, and secondary mica, in fractures and replacing mafic minerals, characterizes the northern, K2O part. A rather high copper concentration (up to 1%) in weathered rocks of the northern part may record a relatively small pyrite concentration which served to prevent leaching by the acidic environment.

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