Abstract
The Pongkor gold deposit located approximately 90 km southwest of Jakarta is well known as the typical low sulfidation (LS) epithermal gold deposit and the largest gold vein deposit in Indonesia. The Pongkor gold mineralisation has been the subject of several geological studies. Determination of the duration of gold mineralisation events, however, is less well understood. The mineralisation events are important for understanding the genesis of ore deposits. This study presents 40Ar/39Ar age results for four adularia samples from Ciguha gold-bearing quartz vein yielding plateau ages of 1.80 ± 0.03 Ma, 2.33 ± 0.32 Ma, and 1.88 ± 0.02 Ma, plus one weighted mean age of 1.95 ± 0.04 Ma. Adularia from the Kubang Cicau gold-bearing quartz veins yielded a 40Ar/39Ar plateau age of 2.02 ± 0.03 Ma. The period of adularia growth in the Ciguha vein may have extended from ca. 2.07 to 1.77 Ma that includes the ages of 1.95 ± 0.04 Ma and 1.88 ± 0.02 Ma. The time interval indicates multiple generations of the adularia. The data suggest that mineralisation of Ciguha may have continued episodically or continuously. The age of adularia from the Kubang Cicau gold-bearing quartz vein (2.02 ± 0.03 Ma) is within the error of the Ciguha vein age and the adularia growth of Kubang Cicau vein reveals at the beginning of Ciguha’s adularia growth. The data suggest that gold mineralisation in the Pongkor deposit for Kubang Cicau and Ciguha veins was initiated at the relatively similar time. The 40Ar/39Ar adularia ages of this study are within error of the previously reported 40Ar/39Ar results (Milesi et al., 1999) but significantly younger than the previously reported K-Ar adularia dating result (Kageyama, 1999 in Rosana and Matsueda, 2002).
Published Version
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