Path: TopS1-Final ProjectGeological Engineering-FITB2017

ALTERASI, MINERALISASI DAN KARAKTERISTIK URAT KUARSA PENAMPANG BARAT–TIMUR TAMBANG TERBUKA BATU HIJAU, SUMBAWA BARAT, NUSA TENGGARA BARAT

ALTERATION, MINERALIZATION AND CHARACTERISTICS OF QUARTZ VEINS SECTION 090 (WEST–EAST) BATU HIJAU OPEN PIT MINING, WEST SUMBAWA, WEST NUSA TENGGARA

Undergraduate Theses from JBPTITBPP / 2017-10-03 14:24:51
Oleh : RYAN AJI FRANS JAYA (NIM : 12013012), S1 - Geological Engineering-FITB
Dibuat : 2017-10-03, dengan 1 file

Keyword : Alterasi, mineralisasi, kerapatan, tipe, urat kuarsa, Penampang 090 Barat–Timur, Batu Hijau

Batu Hijau merupakan salah satu lokasi pertambangan mineral tipe porfiri tembaga-emas yang terletak di bagian barat Pulau Sumbawa, Provinsi Nusa Tenggara Barat, Indonesia. PT. Amman Mineral Nusa Tenggara saat ini sebagai pemegang kontrak karya di Batu Hijau dengan luas wilayah sekitar 12 km x 6 km. Penelitian dilakukan untuk menentukan tatanan geologi, alterasi, mineralisasi dengan studi khusus penyebaran kerapatan dan tipe-tipe urat kuarsa serta hubungannya terhadap kadar Cu dan Au pada penampang 090 (barat-timur) tambang terbuka Batu Hijau.

Data primer didapatkan dari hasil deskripsi pada tujuh sumur inti bor, pengamatan petrografi terhadap 20 sayatan tipis dan lima sayatan poles, XRD (X-Ray Diffraction) dan ditambah dengan data sekunder berupa data assay kadar Cu dan Au. Adapun pengolahan data dan analisis dilakukan secara kualitatif yakni melalui metode overlay (penindihan) antar penampang.

Secara umum, daerah penelitian merupakan kompleks intrusi yang terdiri dari (tua ke muda) Satuan Andesit, Satuan Diorit Kuarsa, Satuan Tonalit Intermediet dan Satuan Tonalit Muda. Zona alterasi dibedakan menjadi 4 zona, yakni Zona Biotit – Aktinolit – Kuarsa, Zona Klorit – Kalsit – Epidot – Aktinolit, Zona Serisit – Klorit – Kalsit – Kuarsa, dan Zona Kaolinit Kuarsa. Mineralisasi utama daerah penelitian dapat dibagi menjadi 3 zona berdasarkan jumlah dominan yang hadir, yakni Zona Bornit, Zona Kalkopirit dan Zona Pirit. Zona kerapatan urat berdasarkan kelimpahannya pada setiap interval pengukuran dibagi menjadi 4 kelas, yaitu kelas Melimpah (>10%), sedang (5-10%), jarang (1-5%) dan sangat jarang (<1%). Tipe urat kuarsa daerah penelitian terdiri dari tipe Mt, A, B, C dan D.

Hasil analisis menunjukkan zona alterasi dan mineralisasi terjadi dalam 3 tahap, yakni tahap awal, transisi, dan akhir yang kehadirannya dikontrol oleh intrusi Satuan Tonalit Intermediet. Perkembangan tipe urat kuarsa Mt dikontrol oleh Satuan Tonalit Muda, sementara tipe urat lainnya dikontrol oleh perkembangan alterasi. Kadar Cu dan Au berhubungan dengan kerapatan dan tipe urat kuarsa tertentu. Semakin rapat urat kuarsa, maka semakin tinggi pula kadar Cu dan Au dengan penyebaran urat kuarsa paling melimpah di bagian tepi Satuan Tonalit Intermediet dan Diorit Kuarsa. Kadar Cu dan Au yang tinggi juga dibawa oleh urat kuarsa Tipe A yang penyebarannya juga berasosiasi dengan Zona Alterasi Biotit – Aktinolit – Kuarsa.

Deskripsi Alternatif :

Batu Hijau is one of the copper-gold mining located in the western part of Sumbawa Island, West Nusa Tenggara Province, Indonesia. PT. Amman Mineral Nusa Tenggara (PT. AMNT) is currently hold contract in Batu Hijau with an area of approximately 12 km x 6 km. This research was conducted to determine the geological setting, alteration, mineralization with special studies of density and quartz vein types as well as its relationship to Cu and Au distribution along section 090 (west–east) of the Batu Hijau open pit mining.

Primary data were obtained from the description of seven drill core wells, petrographic analysis of 20 thin sections and five polished sections, XRD (X-Ray Diffraction) and supported by secondary data in the form of Cu and Au assay data. The data processing and analysis is done qualitatively through overlay method.

In general, the study area is an intrusion complex consist of several units (Late Miocene – Early Pliocene), they are: Andesite, Quartz Diorite, Intermediate Tonalite and Young Tonalite. Alteration zone is divided into 4 zones, they are: Biotite - Actinolite – Quartz Zone, Chlorite - Calcite - Epidote – Actinolite Zone, Sericite - Chlorite - Calcite - Quartz Zone, and Kaolinit - Quartz Zone. The main mineralization of the research area can be divided into 3 zones based on the dominant presence, they are: Bornit Zone, Chalcopyrite Zone and Pyrite Zone. The vein density zone based on its abundance at each measurement interval is divided into 4 classes, they are: abundant (> 10%), moderate (5-10%), rare (1-5%) and very rare (<1%). The quartz vein type of study area consists of Mt, A, B, C and D type.

The results of the analysis show that alteration and mineralization occur in 3 stages, they are: early, transitions, and late stage which is controlled by the intrusion of Intermediate Tonalite. The development of the Mt quartz veins is controlled by the Young Tonalite, while the other vein types is controlled by the development of alteration. There are correlations between Cu and Au grade with the density and distribution of certain quartz vein type. High dense quartz veins are locally occur between Intermediet Tonalite and Quartz Diorite and the density is positively correlated with copper and gold grades. “A” veins also correlated with the high grade of Cu and Au, which associated with Biotit – Actinolite – Quartz Alteration Zone.


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    Ir. Nurcahyo Indro Basuki, M.T., Ph.D.

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