Genesis of orogenic gold in the Latimojong district, South Sulawesi, Indonesia

Research output: ThesisDoctoral ThesisResearch

Abstract

The Awak Mas and Salu Bullo gold deposits are situated in the Latimojong Metamorphic Complex, Sulawesi, Indonesia. These deposits are hosted in pumpellyite- to greenschist-facies metasedimentary and metavolcanic rocks. Total gold contents equals to 50 tonnes Au at 1.4 ppm. The present study focusses on the petrographical, mineralogical, and geochemical study of metasedimentay and metavolcanic rocks, as well as the characteristics of ore-forming fluids, concluding with a genetic model of mineralisation and a metamorphic P-T path of the ore hosting formations. Based on the mineral compositions of chromian spinel, clinopyroxene and whole-rock data, it is inferred that the metavolcanic rocks at Latimojong formed in a suprasubduction zone environment. Chromian spinel spans a wide compositional range (Al- and Cr-rich) and may have crystallized from IAB-type melts at different stages of fractional crystallization. Growing clinopyroxene phenocrysts in the melt trapped floating chromite crystals on their way upward. Metabasites and meta-andesites have low REE concentrations and flat chondrite-normalized patterns. Metasedimentary rocks show negative Eu anomaly, high LREE/HREE ratios, consistent with derivation from continental crust. The results of this study do not support the existence of ophiolite rocks body within the mineralized area in the Latimojong Metamorphic Complex. All microscopically visible gold occurs as inclusions within sulphide (e.g. pyrite) or as crack filling, less commonly free grains occur in quartz. Grain sizes of gold (Au85-88Ag12-15) range from submicroscopic (

Details

Translated title of the contributionGenese der orogenen Goldlagerstätte im Latimojong Gebirge, Süd-Sulawesi
Original languageEnglish
QualificationDr.mont.
Awarding Institution
Supervisors/Advisors
  • Paar, Werner H., Assessor B (external), External person
  • Melcher, Frank, Assessor A (internal)
Publication statusPublished - 2017