Sutarto, Sutarto and Idrus, Arifudin and Harijoko, Agung and Setujadji, Lucas and Meyer, Franz Mechail (2015) VEINS AND HYDROTHERMAL BRECCIAS OF THE RANDU KUNING PORPHYRY Cu-Au AND EPITHERMAL Au DEPOSITS AT SELOGIRI AREA, CENTRAL JAVA INDONESIA. SE Asian Applied, 7 (2). pp. 80-99.
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Abstract
The Randu Kuning prospect is situated at Selogiri
area, Wonogiri, Central Java, Indonesia. This location
is about 40 km to the south-east from Solo
city or approximately 70 km east of Yogyakarta
city. Many Tertiary dioritic rocks related alterationmineralisation
were found at the Randu Kuning area
and its vicinity, including hornblende microdiorite,
hornblende-pyroxene diorite and quartz diorite.
Mineralisation type of the Randu Kuning prospect
was interpreted as porphyry Cu-Au and a number
epithermal Au-base metals deposits in its surrounding.
The closed existing of porphyry Cu-Au and epithermal
Au-base metals type deposits at the Randu
Kuning area produced a very complex of veins and
hydrothermal breccias crosscutting relationship. A
lot of porphyry veins types were found and observed
at the Randu Kuning area, and classified into at
least seven types. Most of the porphyry veins were
cross cut by epithermal type veins. Many epithermal
veins also are found and crosscut into deeply
porphyry vein types. There are genetically at least
two type of hydrothermal breccias have recognized
in the research area, i.e. magmatic-hydrothermal
breccia and phreatomagmatic breccia. Magmatic hydrothermal
breccias are mostly occured in contact be-
*Corresponding author: SUTARTO, Department of
Geological Engineering, Gadjah Mada University. Jl.
Grafika 2 Yogyakarta, Indonesia. E-mail: sutarto -
geo@upnyk.ac.id
tween hornblende microdiorite or quartz diorite and
hornblende-pyroxene diorite, characterized by angular
fragments/clasts supported or infilled by silicas,
carbonates and sulphides matrix derived from hydrothermal
fluids precipitation. Phreatomagmatic
breccias are characterized by abundant of the juvenil
clasts, indicated contact between hot magma
with fluid or water as well as many wall rock
fragments such as altered diorites and volcaniclastic
rock clasts set in clastical matrix. The juvenil
clasts usually compossed by volcanic glasses and
aphanitic rocks in rounded-irregular shape. Both
veining and brecciation processes have an important
role in gold and copper mineralisation of the
Randu Kuning Porphyry Cu-Au and epithermal
Au-base metals deposits, mostly related to the presence
of quartz veins/veinlets containing significant
sulphides, i.e., quartz with thin centre line sulphides
(Abtype) veins, pyrite±chalcopyrite (C type)
veinlets, pyrite+quartz± chalcopyrire±carbonate (D
type) veins of porphyry types as well as epithermal
environment quarts+ sulphides+carbonate veins.
Keywords: Veins, Hydrothermal breccia, Porphyry,
Epithermal
| Item Type: | Article |
|---|---|
| Subjek: | Q Science > QE Geology |
| Divisions: | x. Faculty of Engineering, Science and Mathematics > School of Engineering Sciences |
| Depositing User: | Dr.Ir SUTARTO - |
| Date Deposited: | 22 Jan 2019 07:33 |
| Last Modified: | 22 Jan 2019 07:33 |
| URI: | http://eprints.upnyk.ac.id/id/eprint/18092 |
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