Queensland, Qld, Australia
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The Mount Carbine vein type tungsten deposit is located in the Hodgkinson Province of north Queensland, Australia, some 50 km WNW of Cairns (#Location: 16° 31' 27"S, 145° 7' 55"E).
The Hodgkinson Province/Basin consists of Palaeozoic turbiditic siliciclastics with subordinate limestone, chert and mafic volcanics. The oldest sequences are Ordovician siliciclastic rocks that are located along the western margin of the province, adjacent to the Palmerville Fault which separates the basin from the Proterozoic Etheridge and Savannah Provinces of the North Australian Craton to the west (GeoScience Australia Website).
Silurian-Devonian rocks in the Hodgkinson Province include the Chillagoe Formation (mainly limestone, chert, mafic volcanic rocks and sandstone), and the Hodgkinson Formation (mainly sandstone, siltstone and mudstone, with subordinate chert, mafic volcanic rocks and conglomerate), which makes up most of the province. Mafic volcanic rocks in the Hodgkinson Formation, which include basalt, basaltic andesite and andesite/dacite, have been considered to have a MORB-like geochemical signature, although other data suggest (e.g., Nb depletion) a possible relationship to subduction. These rocks are also intruded by the 347±6 Ma Emerald Creek Microgranite, which is partially stoped out by the Permian Tinaroo Granite of the Kennedy Igneous Association (GeoScience Australia Website).
The Hodgkinson Basin sequence is overlain by restricted Carboniferous to Triassic non-marine successions including conglomerate, coal measures, volcanic rocks and sandstone (GeoScience Australia Website).
The Mount Carbine deposit occurs as a structurally controlled swarm of quartz veins hosted within the Devonian Hodgkinson Formation, a sequence of clastic sedimentary and basic volcanic rocks. Mineral assemblages within the mafic volcanic rocks indicate low-grade regional metamorphism (De Roo, 1988).
At Mount Carbine, the Hodgkinson Formation has been subdivided into a coarse-grained association of sedimentary rocks, dominantly conglomerates, arkoses
and turbidite-type graywackes, and a fine-grained association of interbedded siltstone and shale. A basic volcanic unit with bedded cherts separates the two clastic sequences, and acts a marker in large-scale upright folds that deform the sequence (De Roo, 1988).
The deposit lies within the thermal aureole of the Permian S-type granite of the Mossman Batholith which is exposed <5 km to the NE and covers an area of >400 km2 (De Roo, 1988).
In the aureole of the granite, the mafic metavolcanic rocks have locally been altered to a calc-silicate skarn assemblage (Forsythe, 1983), whilst the sedimentary rocks have been recrystallised to hornfels, with formation of pseudomorphic phyllosilicate aggregates after cordieritc or andalusite
porphyroblast (De Roo, 1988).
De Roo (1988) explains the formation of the deposit in terms of mineralisation being concentrated in favourable structural sites, created by three major
deformations that affected the host succession.
D1 produced upright folds with a vertical axial plane cleavage (S1), followed by D2 which resulted in conjugate kinking of S1, where this cleavage is strongly developed, and then by granitic intrusion. Contact metamorphic assemblages in the contact metamorphic aureole surrounding the granite were established before local recumbent folding by D3 of S1. During the late stages of this latter event, vein mineralization developed along D2 kink planes in sites of high D1 strain, where capped by domains of D3 folding (De Roo, 1988).
Evolution of this mineralisation at Mount Carbine mine commence with an early stage of fracture dilation, marked by tourmaline infill and associated wall-rock alteration, with fibrous 'crack-seal' microstructures indicating repetitive tensile failure accompanying tourmaline deposition. Subsequent major dilations are marked by veins of non-fibrous quartz and feldspar, and ore-grade wolframite. In similar mineralisation at other nearby prospects, these veins merge with greisen veins and granite dykelets, supporting a granite related hydrothermal model for the origin of the tin and tungsten in the area. However, the late D3 vein mineralisation was, preceded by the local formation of a differentiated layering( S3), and of sets of barren veins a long S3 and D2 kink planes. Both the layering and barren veins postdate the growth of the contact metamorphic assemblage around the undeformed granite (De Roo, 1988).
The ore veins comprise quartz-feldspar-muscovite with wolframite and lesser scheelite. The wolframite has been attributed to granitic hydrothermal activity (Plumridge, 1975; Gregory et al., 1980; Kwak et al., 1982) related to the adjacent Mossman batholith. Scheelite was introduced into the ore veins at a late stage, together with carbonate and base metal sulphides (Forsythe, 1983).
De Roo (1988) observed that on the basis of crosscutting relationships, separate sets of cm-scale quartz veinlets can be identified at attitudes normal to the folded layering of bedding and S1. Their shape and orientation relative to D1 structural elements suggests D1 syn-deformational vein formation by hydraulic
fracturing at pore fluid pressures exceeding the least compressive stress plus the tensile strength of the rock (Phillips, 1972, 1986; Beach, 1977; Etheridge
et al., 1984). Slightly larger quartz tension veins (Va) formed parallel to S2, marking the kink zone exposed in the pit. Upward along the vertical D3 strain gradient, these veins have been rotated toward shallower dips, whilst some are tightly folded about sub-horizontal axes in the domain of high D3 strain. De Roo (1988) therefore argues these quartz veins formed at some stage between late D2 and early D3 deformation.
Thermal metamorphism at Mount Carbine involved silicification and recrystallisation of these veins and their matrix. The development of hornfels was accompanied
by pervasive tourmaline alteration and the introduction of quartz-tourmaline veins a few cm in width. Local intense alteration along these veins resulted in massive replacement of phyllosilicate-rich hornfels by biotite, tourmaline and minor quartz, and the replacement of quartz-rich rocks by quartz, with minor biotite and tourmaline. Consequently, the massive alteration pattern was also controlled by the preexisting lithology and structure, where preserved in the hornfels (De Roo, 1988).
The deposit contained 28 Mt @ 0.1% WO3, but was amenable to low strip open pit mining and cheap photometric ore sorting technology.
For more detail see the reference(s) listed below.
The most recent source geological information used to prepare this summary was dated: 1990.
Record last updated: 22/6/2016
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
References to this deposit in the PGC Literature Collection:
De Roo, J A 1988 - Structural controls on the emplacement of the vein-type Tungsten-Tin ore at Mount Carbine, Queensland, Australia: in Econ. Geol. v83 pp 1170-1180|
Forsythe D L, Higgins N C 1990 - Mount Carbine Tungsten deposit: in Hughes F E (Ed.), 1990 Geology of the Mineral Deposits of Australia & Papua New Guinea The AusIMM, Melbourne Mono 14, v2 pp 1557-1560|
Plumridge C L 1975 - Mount Carbine tungsten reef swarm: in Knight C L, (Ed.), 1975 Economic Geology of Australia & Papua New Guinea The AusIMM, Melbourne Mono 5 pp 762-764|
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