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Deposit Synonyms
MANX A1; MANXMAN WEST
Mineral District
Deposit Summary
drillhole DD86EN25 intersected 31m of 140ppm U, including 7.5m of 231ppm U, between 216.9-248.1m in feldspathic and chloritically altered magentite-rich breccias. Potential for low-grade magnetite ore.
Deposit Description
MANXMAN A1, one of a series of near coincident bullseye magnetic and gravity anomalies, part of a larger, complex, gravity and aeromagnetic feature thought to be sourced by a large gabbroic to granitic pluton. Ground magnetics in the early 1980's initially resolved the target into the Manxman A and B prospects, which was subsequently further resolved into 6 discrete magnetic anomalies, designated Manxman A1 to A6. Manxman A1 prospect was identified as a bullseye magnetic anomaly with dimensions 1200m by 500m, associated with a gravity anomaly.
Modelling sugested the presence of 2 parallel, steep dipping, EW-trending prisms of rock each ~200m wide, and ~100m apart.
Follow up drilling of Manxman A1 in the late 1980s to early 1990s identified a sequence of brecciated, iron oxide-rich, metasomatic metasediment, and meta-igneous rock of presumed Palaeoproterozoic age, beneath ~100m of flat lying cover sediment. Basement rock has been grouped into a suite of pink leucocratic gneiss, and a sequence of metasedimentary granulites (psammitic, pelitic quartzo-feldspathic, and intercalated magnetite-bearing psammite to possible BIF. U=Pb zircon analyses of surface samples from further north suggest a depositional age of 1750 +/1 6Ma.
There were significant intervals of magnetite-rich contact metamorphic/metasomatic rock, also magnetite-rich gabbro, felsic igneous rock, and felsic metasediment. The skarn-like assemblage appeared to be located within and marginal to the previously mentioned gabbroic and granitoid bodies. Metamorphic grade was upper amphibolite to lower granulite facies. it has not been determined as to the level of introduced iron versus iron remobilised from host sediment. U-Pb SHRIMP ages on migmatitic segregation suggest melting age of 1736 +/-14Ma.
Intervals of massive, brecciated magnetite, and hematite were often closely associated with anomalous Cu-U-Au values. The magnetite-bearing rock was worthy of consideration as a low-grade iron ore resource. Age dates (titanate, U-Pb) indicate Cu-Au mineralisation age of 1567 +/-10Ma.
Best iron interval was drill hole DD88EN43, with an interval of 402m of interbanded iron-rich and felsic lithologies from 119-521m for 302m of iron-rich section @ ~35%Fe. Best Cu to 16600ppm, 356m, EN61, 2.5ppmAu, 184.42m in EN24, 483ppmCo 222.9m in EN25. Best uranium intersection was from 216.9-248.1m in drillhole DD86EN25, with 31m of 140ppm U, including 7.5m of 231ppm U, in feldspathic and chlorite-altered magnetite-rich breccia. Also DD86EN24, 6.56m @ 184ppmU3O8 from 215.2m, and 86EN35, 6m @ 147ppmU3O8 from 260m. On the basis of 7 holes the iron-rich body would appear to be ~1km long EW, width ~150m at west end, and >600m at east end, and traced to depth >350m.
More details in Hampton, S., 1997, BSc. thesis submitted to Department of Economic geology of James Cook University of North Queensland.
Discovery Year
? 1986
Commodities
Iron, Copper, Gold, Uranium
Ore Minerals
Chalcopyrite, Gold, Hematite, Magnetite, Pyrrhotite, Uraninite
Gangue Minerals
Actinolite, Apatite, Biotite, Carbonate, Chlorite, Feldspar, Pyrite, Quartz
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