Geoscience Reference
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is a good modern analogue for Mississippi Valley-type mineralization, and
in particular the best modern example is the emergent forebulge of the
Kepulauan Aru (Aru Islands) in neighboring Indonesia. Other lines of evi-
dence support this hypothesis. For example, recent work
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has recognized
significant natural hydrocarbon seeps (methane plumes and associated tube
worms, some of which are coated with manganese carbonate) on the seafloor
on the Yampi Shelf and Arafura Sea. These seeps are considered strong evi-
dence for an active petroleum system in this area.
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Hydrocarbons such as
bitumen are common accessory materials in Mississippi Valley-type lead-
zinc deposits and provide a link between petroleum and base metal sulfide
formation. Further survey work in NW Australian waters is required to
assess base metal potential.
A cruise (GABSEEPS, FR01/2001)
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along the edge of the Great
Australian Bight tested the hypothesis for Mississippi Valley-type lead zinc
mineralization, and possibly also for a form of uranium mineralization asso-
ciated with hydrothermal “warm seeps” venting basin brines or fluids ris-
ing up faults from basement.
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It was anticipated that such sites might
host mineral-rich deposits, or that the vent fluids might have compositions
implying operation of subsurface ore-forming processes. Even though no
evidence of hydrothermal seepage or associated deposits was found, inves-
tigations of this nature can yield important results for future science and
expedition planning.
5. Ophiolite-Hosted Copper
A major strike slip fault marks the boundary between the Australian and
Pacific plates via the Alpine Fault in South Island New Zealand and extend-
ing SW to Macquarie Island, approximately 1500 km SSE of Tasmania in
the Southern Ocean. This fault marks the only active plate boundary within
Australia's marine jurisdiction. A triple junction to the south of Macquarie
Island links the Macquarie Ridge Complex with the Southeastern Indian
Ridge and the Pacific-Anatarctic Ridge. Uplifted blocks of oceanic crust
formed at the Australia-Pacific spreading center between 12 and 9 Ma are
exposed on World Heritage Listed Macquarie Island.
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,
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This structurally
dismembered ophiolite exposes pillow basalt, sheeted dykes, gabbro and
peridotite; and preserves many primary seafloor and sub seafloor features
such as rift-related and transfer-related structures at the fossil spreading
ridge system. These structures acted as conduits for hydrothermal fluids
