Characteristics of Ore-Bearing Vein in Banyuresmi, Cigudeg District, West Java Province: Constraints from Geological, Alteration, and Mineralization Aspects
DOI:
https://doi.org/10.33332/jgsm.geologi.v26i2.902Abstract
The study area of the ore-bearing vein system is
located in Banyuresmi, Cigudeg District, ±13.6 km from
the Gunung Pongkor deposits or ±45 km from Jakarta.
The ore-bearing veins system is being operated by small
scale and traditional gold mines. Up to now, no peer
reviewed papers have been published on the geological
conditions and ore characteristics in this area. This study
aims to determine the distribution of lithology, geological
structure, alteration zonation, and the mineralization
characteristics of ore-bearing veins in the Banyuresmi area.
To achieve the objectives, several research methods were
employed, grouped into fieldwork (rock/vein sampling and
geological structures measurement) and laboratory analysis
(6 rock samples for petrography and 6 vein samples for
ore microscopy). The results of this study indicate that
the stratigraphy of the study area consists of porphyritic
andesite units, which are overlain by lapilli tuff units and
then followed by the formation of colluvial units. The
geological structures that develop in the area of study,
represented by normal faults, strike-slip faults, and thrust
faults, are produced from the average value of maximum
stress (σ1) for all tectonic phases, which have trend
values of N32°E and N210°E (NE-SW). Hydrothermal
alteration in the Banyuresmi vein system is divided into
three zones: propylitic (chl-sm±ser±cb), argillic (il±kao),
and silicification (qz). Mineralization in the area of study
is dominated by ore minerals such as galena, sphalerite,
pyrite, chalcopyrite, digenite, covellite, bornite, hematite,
and pyrrhotite. These ore minerals are found in veins with
quartz and quartz-clay composition, which consist of
various textures including crustiform-colloform, massive, comb, zoning, dogteeth, cockade, etc. The veins are
estimated to have varying orientations, including NW-SE,
E-W, and NE-SW. Based on the characteristics of this study,
the Banyuresmi ore vein system shows a propensity to be a
low sulfidation epithermal system deposit type.
Keywords: Ore-bearing vein, low sulfidation epithermal,
hydrothermal alteration, Banyuresmi, West Java
Abstrak
Sistem urat pembawa bijih ini terletak ±13.6 km
dari endapan Gunung Pongkor atau ±45 km dari Jakarta.
Sistem urat pembawa bijih ini dioperasikan oleh tambang
emas skala kecil dan tradisional. Hingga saat ini, belum
ada publikasi makalah yang memuat kondisi geologi terkait
karakteristik urat pembawa bijih di daerah tersebut. Studi
ini bertujuan untuk mengetahui persebaran litologi, struktur
geologi, dan zonasi alterasi, serta menentukan karakteristik
mineralisasi dari urat pembawa bijih di daerah Banyuresmi.
Untuk mencapai tujuan tersebut, digunakan beberapa
metode penelitian yaitu pekerjaan lapangan (pengambilan
sampel, dan pengukuran kedudukan struktur geologi) dan
analisis laboratorium (analisis petrografi pada 6 sampel
batuan serta analisis mineragrafi pada 6 sampel urat).
Hasil dari penelitian ini menunjukkan bahwa stratigrafi
daerah penelitian terdiri dari Satuan Andesit Porfiritik
yang ditindih oleh Satuan Lapili Tuf dan kemudian disusul
oleh terbentuknya Satuan Koluvial. Struktur geologi yang
berkembang pada daerah penelitian berupa sesar normal,
sesar geser, dan sesar naik dihasilkan dari harga rata-rata
tegasan maksimum (σ1) seluruh fase tektonik yang memiliki
nilai tren N32°E dan N210°E (NE-SW). Alterasi hidrotermal
pada sistem urat Banyuresmi terbagi kedalam tiga zona
yaitu propilitik (chl-sm±ser±cb), argilik (il±kao), dan
silisifikasi (qz). Mineralisasi daerah penelitian didominasi
oleh mineral bijih seperti galena, sfalerit, pirit, kalkopirit,
digenit, kovelit, bornit hematit, dan pirhotit. Mineral bijih
tersebut dijumpai pada urat kuarsa dan kuarsa-lempung
yang terdiri dari berbagai macam tekstur mencakup
crustiform-colloform, masif, comb, zoning, dogteeth,
cockade, dll. Urat-urat tersebut diperkirakan memiliki orientasi yang bervariasi, yaitu NW-SE, E-W, dan NE-SW.
Berdasarkan karakteristik pada penelitian ini, sistem urat
bijih Banyuresmi menunjukkan adanya kecenderungan
sebagai tipe endapan sistem epitermal sulfidasi rendah.
Kata Kunci: Urat pembawa bijih, epitermal sulfidasi
rendah, alterasi hidrotermal, Banyuresmi, Jawa Barat
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Copyright (c) 2025 Ali Rifqi ` Alamudi, Mochamad Risyad Rizkyafdhal, Muhammad Bintang Firdaus, Dian Yesy Fatimah, Dimas Setya Kusuma Wahjoedi
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