TIN AND TUNGSTEN DEPOSITS IN NORTHEAST QUEENSLAND, AUSTRALIA: PAST, PRESENT, AND PROSPECTIVITY (original) (raw)

2018, Proceedings of the IAGOD symposium

Northeast Queensland of Australia is an important Sn-W-Mo-Au mineralized province in Australia, particularly for Sn and W, which includes ~10% of Australia's Economic Demonstrated Resources (EDR) of Sn and ~13% of the country's EDR of tungsten (Chang et al, 2017). Sn-dominant deposits mainly occur in three districts: the Kangaroo Hills, Herberton and Cooktown districts. The W-dominant deposits occur only in the northeast Mt Carbine-Watershed area. W-Mo deposits have been found in both the Herberton (e.g., Wolfram Camp) and Kangaroo Hill districts. To discern differences between "fertile" and "non-fertile" igneous rocks associated with Sn-W-Mo mineralization and reveal the genetic links between coeval intrusive and extrusive rocks, we integrate whole rock geochemistry, geochronology and Hf isotope signatures of igneous zircons from contemporaneous plutonic and volcanic rocks from the Herberton Sn and W-Mo mineral field. The 310-300 Ma intrusive rocks and associated intra-plutonic W-Mo mineralization formed from relatively oxidized magmas after moderate degrees of crystal fractionation. The geochemical and isotopic features of the coeval volcanic succession are best reconciled utilizing the widely-accepted volcanic-plutonic connection model, whereby the volcanic rocks represent fractionated derivatives of the intrusive rocks. The volcanic rocks of 335-310 Ma (Sn formation stage) are compositionally less evolved than the coeval intrusive rocks. In this case, we propose that the most fractionated magmas were not lost to volcanism, but instead were effectively retained at the plutonic level, which allowed further localized build-up of volatiles and lithophile metals in the plutonic environment. Given the common occurrence of volcanic and plutonic rocks associated with Sn-W-Mo mineralization worldwide, we suggest that a proper understanding of plutonic-volcanic connections can assist in assessment of regional-scale mineralization potential, which in turn can aid strategies for future ore deposit exploration. The Wolfram Camp Mine deposit is a greisen type W-Mo deposit. The host rock of the deposit is Late Carboniferous James Creek granite and which has locally intruded Hodgkinson Formation sandstone. The orebodies contain wolframite and molybdenite occur as pipe-like bodies of quartz in the roof zone of the intrusion. Alteration associated with the Wolfram Camp mineralization is mainly greisen type. The alteration can be divided into quartz-rich greisen zones, muscovite-rich greisen zones and greisenized granite zones with decreasing alteration levels. The mineralization in the study area are closely related to post-intrusive hydrothermal events and can be divided into several stages. The major ore minerals, wolframite and molybdenite, formed during the greisen stage, and base metal sulphide minerals and scheelite formed in later sulphide and calcite stages. Fluid inclusion studies was conducted on the ore bearing quartz crystals in the pipes. The homogenization temperatures of the fluid inclusions quartz containing wolframite are about 410 °C. Results from a stable isotope study suggest that the source of the hydrothermal fluid related to the formation of the wolframite, molybdenite and base metal sulphides is purely magmatic. However, the fluid responsible for the introduction of the calcite is a combination of magmatic water and meteoric water. The Mt Carbine quartz-wolframite-scheelite sheeted vein deposit is hosted in Ordovician to Devonian Hodgkinson Formation metasedimentary rocks. Field observation and drill core logging have provided evidence for a five stage paragenetic sequence of mineralization and veining, with two of the stages having significant W mineralization. Wolframite is typically euhedral and occurs in quartz veins, while scheelite occurs as (1) euhedral grains in quartz vein and, (2) pseudomorphing wolframite grains or cutting across wolframite grains as veinlets. This observation is consistent with the scheelite CL images and in-situ composition variation. The LA-ICP-MS zircon U-Pb dating results reveal the magmatic activities occurred during 300-265 Ma. Molybdenite Re-Os age and muscovite 40Ar-39Ar ages are between 285-275 Ma. Fluid inclusion studies reveal that most of the inclusion are primary and distributed in assemblages or isolated, with homogenization temperatures ranging from 290 to 210 °C. Laser Raman analysis identified CH 4 in vapour bubbles. Together with H-O-S isotopic compositions, our data indicate that both magmatic fluid and metamorphic water contributed the formation of Mt Carbine W deposit. The Watershed scheelite deposit lies within the Mossman Orogen, which comprises deformed Silurian-Ordovician metasedimentary rocks of the Hodgkinson Formation by Carboniferous and Permian granites of the Kennedy Igneous Association. Multiple felsic dykes cut cross the metasedimentary rocks at Watershed including: (a) monzonite dyke (~350 Ma); and (b) dioritic, granitic plutons and dykes (281-271 Ma). A first non-economic A | 35