| Summary: | The Schwaner Mountains area is located in the Southwest Kalimantan
Islands, Indonesia. After the deposition of Permo-Carboniferous sediments on a
basement complex of crystalline schists and the emplacement of gabbroic plutonic
masses, the zone of the Schwaner Mountains had been invaded by large granitic to
quartz-dioritic (tonalitic) batholiths. Iron ore mineralization is formed with these
granitic intrusions within the Schwaner Mountains. The purpose of this research is
to study of the style of each iron ore mineralization and their mineralogical and
geochemical characteristics of different iron ore mineralizations associated with
granitic intrusions as well as the geochemical characteristics of granitic rocks.
During this research, four iron ore mineralizations are visited to study their nature,
style, petrographic studies and significant geochemical characteristics of each iron
ore. Ruwai iron ore mineralization is directly associated with dioritic intrusion and
the iron ore mineralization occurs as the massive iron ore at the contact of
intrusion and volcanic unit from the hanging wall. The iron ore mineralization
style is characterized by skarn style mineralization and the principle ore minerals
are magnetite and hematite that occur within the proximal garnet zone. The next
iron ore mineralization Sejambuan iron ore occurs as a massive body at the
contact zone between granite intrusion and volcanic andesite unit which is highly
altered with kaolinite and illite mineral assemblages. The iron ore mineralization
is associated with alteration envelopes and alterations are seemed to be products
of hydrothermal event. The Ombangan iron ore mineralization is located near the
Ruwai iron ore mineralization and the iron mineralization here occurs as massive
magnetite associated with granite intrusions and volcanic-sedimentary units. The
mineralization style is considered as skarn style mineralization associated with
intrusion. The evidence of skarn mineral assemblages garnet occurs within the ore
zone and those are replaced by magnetite. The last iron ore mineralization, the
Bukit Besi iron ore mineralization, is different from the other three iron
mineralizations in area. The principle iron ore minerals hematite occurs associated
with the alternating band of microcrystalline quartz (chert).
The geochemical signatures of each iron ore are entirely composed of Fe2O3
and slightly different variable concentration of other major element oxides. The
encountered incompatible trace elements are generally low concentrations except
the transition and chalcophile elements are variable for each iron deposit. The rare
earth elements are generally depleted and most of their REE chondite-normalized
patterns display fractionation LREE in respect to HREE and some are displayed
with distinct positive Ce and Eu anomalies.
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