#TITLE_ALTERNATIVE#

• Main Author: VARIANTI PANGAU (Nim:12011046); Tim Pembimbing : Prof.Dr.Ir. Emmy Suparka; Ir Teti Indriati, NERISSA
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/20349
• Institution: Institut Teknologi Bandung

The research area is located in Block A Contract of Work area under the operation of PT Freeport Indonesia, Ertsberg Mining District, Mimika District, Papua. Research is conducted using core data from 6 boreholes: BG403W-01, BG389W- 01, BG330W-01, BG320W-01, BG209W-01, and BG207W-01. Research results are approached by macroscopic analysis, microscopic analysis which includes petrography and mineragraphy analysis, and contour digitations of geochemical assay element to determine lithostratigraphy units, alteration zones, mineralization zones, and secondary minerals paragenesis. Stratigraphy of the research area can be divided into 5 lithostratigraphy units, ordered from oldest to youngest: (1) Quartz Arenite Sandstone Unit, (2) Claystone Unit, (3) Quartz Wacke Sandstone Unit, (4) Shale Unit, all of which belong to the <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> late Cretaceous Ekmai Formation, and (5) Dolostone Unit from Paleocene Waripi Formation deposited conformably overlying Ekmai Formation. Research area has been affected by hydrothermal alteration processes with the intensity ranging from unaltered to totally altered and is divided into 3 zones based on mineral assemblages: (1) Magnetite-Pyrite-Calcite Zone (skarn), (2) Calcite-Tremolite-Actinolite±Chlorite Zone (skarn), and (3) Quartz-Chlorite- <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> Calcite-Actinolite-Epidote Zone (propylitic). The main oremineral found disseminated within rocks in research area is chalcopyrite (CuFeS2). Based on geochemical assay value on Cu with 2% cutoff grade, research area is divided to 3 mineralization zones: (1) 1-2% Cu Zone, (2) 2-4% Cu Zone, and (3) >4% Cu Zone. High concentration zones of Cu (>2%) is found associated with Calcite- Tremolite-Actinolite±Chlorite Zone. Pliocene intrusion caused contact metamorphism to happen at research area. Magmatic hydrothermal fluid then infiltrated to calcareous rocks in the research area (Dolomite Unit) and caused prograde phase of skarn alteration, forming anhydrous minerals. Subsequently the retrograde phase of skarn alteration <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> <br /> occurred causing hydrous minerals to replace anhydrous minerals formed earlier. This result is particularly shown in Calcite-Tremolite-Actinolite±Chlorite Zone. Sulphide minerals enrichment occurred concurrently with retrograde phase of skarn alteration.