Valley Bore, Spriggs Creek Bore (Spriggs Bore), Ambalindum Station, Harts Range, Central Desert Region, Northern Territory, Australiai

Regional Level Types
Valley Bore	- not defined -
Spriggs Creek Bore (Spriggs Bore)	- not defined -
Ambalindum Station	- not defined -
Harts Range	Mountain Range
Central Desert Region	Region
Northern Territory	Territory
Australia	Country

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Located in the Entia dome area.

The Valley Bore has been used to label the northern Entia Dome area of the east Harts Range, with local scheelite deposits, and more general geologic descriptions of country rock. Specimens which come from the area are generally labelled either the Entia Valley, or Spriggs Creek Bore. Isolated locations have produced gem quality material, including what is called the 'Iolite Enclave', with Shaw's Deposit to the north-east of Valley Bore, and various epidote and kyanite sites. Valley Bore is 16 kilometres south of the Plenty Highway, along the main track into Entia Valley. Mindat map shows the bore site itself.

In a general sense across the northern Entia Dome are the following rock units. The Brady Gneiss is the uppermost unit within the Valley Bore area, consisting of quartz-plagioclase-biotite-muscovite-almandine gneiss, with locally sillimanite. Then the Irindina Gneiss with a similar composition. The Bruna Gneiss quartz-plagioclase-microcline-biotite gneiss, with porphyroblasts of microperthitic microcline, or blue-grey plagioclase, locally amphibolite, and almandine porphyroblasts. The lower most unit in the Valley Bore area is the Entia Gneiss of quartz-plagioclase-microcline gneiss, with minor biotite and muscovite, locally sillimanite, and garnet, with enclaves of quartz-muscovite-biotite-kyanite schist.

Locally at Valley Bore, the area consists of clinozoisite-hornblende-corundum; biotite-kyanite-corundum schist; quartz-epidote rock; gedrite-epidote rock; gedrite bearing gneiss; cordierite bearing gneiss; pegmatites; metamorphic mafic igneous rocks.

The Valley Bore Area contains a band of calc-silicate rock averaging 9 feet wide, containing rare earth mineralisation traced for 3 kilometres length, trending north-south, cut by younger east-west trending pegmatites. The Walter Smith prospect located under this sub-section may be part of this. At the contact mineralisation consists of magnesite, actinolite, fluorspar, calcite, microcline, and small patches of scheelite. Half a mile south of the bore scheelite is found as float shed from small scheelite stringers.

The main zone of mineralisation is hosted by epidote-garnet-calcite rocks 10-90 feet wide, variable dipping, outcropping discontinuously for 3 kilometres, with numerous quartz veins, locally displaced by faults, and pegmatites. Scheelite is found as small disseminations in epidote and quartz veins.

Specimen material within the vicinity of Valley Bore is unknown, but appears possible. Scheelite and rare earth minerals in quartz veins cutting calc-silicate rocks, is reported 2 kilometres west of Valley Bore. Alluvial scheelite, with trace molybdenum and bismuth minerals is reported 5 kilometres east of Valley Bore.

Mineral List

3 valid minerals.