| Summary: | Sedimentary manganese layers have been discovered in Supul, South
Central Timor Regency, East � Nusa Tenggara Province. The manganese layers is
associated with deep sea sedimentary rock and interbedded with redish to redish
brown claystone. The deposit shows the spatial linkage with mud volcano
intrusion. Physically, the manganese layers range from 2 mm to 4 cm in width,
compact, lenticular, solid, and strongly deformed. Mineralogically, it is
composed of manganite mineral (MnO(OH)) as primary mineral, pyrolusite
(MnO2), lithiophorite (Al,Li) MnO2(OH)2, and associated with gangue minerals
including calcite (CaCO3), silica (SiO2), limonite (FeO(OH), hematite (Fe2O3) and
Barite (BaSO4).
There are two form types of manganese ores that found in study area, that is
manganese nodule and manganese layers. Mineralogically, the manganese nodule
composed of manganite that associated with limonite. It has grade of 62.72 and
69.42 wt.% MnO. Whereas manganese layers classified into three form types. The
first type is pyrolusite and has grade of 66.05 wt.% MnO. The second and third
have different in the hardness. Mineralogically, the second and third types of
manganese layer composed of manganite as primary manganese mineral, and also
lithiophorite and pyrolusite. It has grade 63.33%-71.57 wt.% MnO. In general iron
in Mn Ore is very low ranging from 0.2 to 1.54 wt.% Fe2O3, hence, Fe / Mn ratio
is very low of 0.0025-0.0691%, which typically indicates sedimentary origin. This
sedimentary origin is supported by petrologic and petrographic data showing
layered structure of manganite and lithiophorite, as well as the degradation of
crystal/grain size manganite.
Geochemical analysis shows that manganese ore is non hydrothermal and
was precipitated in reduction condition according to REE normalization graphic
that revealing similar distribution pattern of REE with timor nodule, pacific
hydrogenous and nodule hydrogenous that is the existing of Ce positive anomaly,
graphic data of Co+Ni vs. As+Cu+Mo+Pb+V+Zn and the calculation of Ceanomaly.
Moreover, this nodule manganese views hydrogenous deposit based on Al and Si
concentration, and supported by the positive correlation of Mn with Cu, Ni and
Zn, whereas the manganese layers is detrital diagenic deposit (remobilization of
manganese in the water column of the ocean, precipitated and sedimented on the
deep sea bottom) as well as reveals the effect of hydrothermal, which is the
positive correlation of Mn and As. This is proven by the presence of quartz and
barite veinlets cutting the Mn layers, manganite recrystallization along vei layers
and the presence of pyrite.
Geochemically supports the analysis mineralogically that is manganite
which is one type of mineral manganese is relatively stable and in the solid phase
has a balance of the sea water and are often not stable in oxidizing conditions so it
was replaced by pirolusit.
Based on field data and analysis of laboratory data, it shows that the
formation of manganese layers deposit in study area is assumed due to the
remobilization of manganese in the water column of the ocean, while the
manganese nodules are hidrogenous deposits, formed by the chemical reaction
within sea water shaping unsolvable particle in sea water so that it will be sink
into the bottom of sea floor/precipitation of metals from sea water.
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