Modeling the Role of Sodic Alteration in the Genesis of Iron Oxide-Copper-Gold Deposits, Eastern Mount Isa Block, Australia

Oliver, Nicholas H.S.; Cleverley, James S.; Mark, Geordie; Pollard, P. J.; Fu, Bin; Marshall, Lucas J.; Rubenach, Michael J.; Williams, Patrick J.; Baker, Timothy D.

doi:10.2113/gsecongeo.99.6.1145

Cited by 208 publications

(35 citation statements)

References 58 publications

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“…2D,E; see also Mark & Foster 2000), have been dated (U-Pb zircon) at 1529 ± 4 to 1523 ± 3 Ma (Page & Sun 1998;Pollard et al 1998). deJong & Williams (1995 and Oliver et al (2004) identified veins and breccias with distinctive post-regional metamorphic albite alteration throughout the Cloncurry District, similar to that displayed in the breccias described here. Metasomatic titanite in those rocks was produced by Na-Ca alteration of biotite, yielding U-Pb titanite ages of 1527 ± 7 to 1521 ± 5 Ma (Oliver et al 2004), within error of the nearby intrusions.…”

Section: Attributes Of Breccia Clasts and Matrixsupporting

confidence: 73%

“…deJong & Williams (1995 and Oliver et al (2004) identified veins and breccias with distinctive post-regional metamorphic albite alteration throughout the Cloncurry District, similar to that displayed in the breccias described here. Metasomatic titanite in those rocks was produced by Na-Ca alteration of biotite, yielding U-Pb titanite ages of 1527 ± 7 to 1521 ± 5 Ma (Oliver et al 2004), within error of the nearby intrusions. The Mt Margaret Granite lies several kilometres east of the Ernest Henry deposit, and has a U-Pb zircon age of 1530 ± 8 (Page & Sun 1998), similar to U-Pb rutile of 1538 ± 37 Ma and U-Pb titanite ages of 1529 ± 11 Ma for pre-to syn-mineralization alteration at Ernest Henry (Mark et al 2006).…”

Section: Attributes Of Breccia Clasts and Matrixmentioning

confidence: 81%

“…3B). The mineralogy of the clasts and matrix is not unique to this particular breccia type -widespread albite alteration with accessory calc-silicate minerals and iron oxides occurs in association with many of the breccia types, veins and pluton carapaces throughout the district (deJong & Williams 1995;Mark 1998;Oliver et al 2004).…”

Section: Attributes Of Breccia Clasts and Matrixmentioning

confidence: 99%

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Granite‐related overpressure and volatile release in the mid crust: fluidized breccias from the Cloncurry District, Australia

Oliver¹,

Rubenach²,

Fu³

et al. 2006

Geofluids

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The source and transport regions of fluidized (transported) breccias outcrop in the Cloncurry Fe-oxide-Cu-Au district. Discordant dykes and pipes with rounded clasts of metasedimentary calc-silicate rocks and minor felsic and mafic intrusions extend several kilometres upwards and outwards from the contact aureole of the 1530 Ma Williams Batholith into overlying schists and amphibolites. We used analytical equations for particle transport to estimate clast velocities ( ‡20 m sec )1 ), approaching volcanic ejecta rates. An abrupt release of overpressured magmatic-hydrothermal fluid is suggested by the localization of the base of the breccias in intensely veined contact aureoles (at around 10 km, constrained by mineral equilibria), incorporation of juvenile magmatic clasts, the scale and discordancy of the bodies, and the wide range of pressure variation (up to 150 MPa) inferred from CO 2 fluid inclusion densities and related decrepitation textures. The abundance of clasts derived from depth, rather than from the adjacent wallrocks, suggests that the pressure in the pipes was sufficient to restrict the inwards spalling of fragments from breccia walls; that is, the breccias were explosive rather than implosive, and some may have vented to the surface. At these depths, such extreme behaviour may have been achieved by release of dissolved fluids from crystallizing magma, in combination with a strongly fractured and fluid-laden carapace, sitting under a strong, low permeability barrier. The relationship of these breccias to the Ernest Henry iron-oxide-Cu-Au deposit suggests they may have been sources of fluids or mechanical energy for ore genesis, or alternately provided permeable pathways for later ore fluids.

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Section: Attributes Of Breccia Clasts and Matrixsupporting

confidence: 73%

Section: Attributes Of Breccia Clasts and Matrixmentioning

confidence: 81%

Section: Attributes Of Breccia Clasts and Matrixmentioning

confidence: 99%

See 1 more Smart Citation

Granite‐related overpressure and volatile release in the mid crust: fluidized breccias from the Cloncurry District, Australia

Oliver¹,

Rubenach²,

Fu³

et al. 2006

Geofluids

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“…Fluids can act as catalysts during mineral transformations and their chemical composition can dramatically change the rock composition and mineralogy (e.g. Ettner et al, 1993;Oliver et al, 2004;Clark et al, 2005) by dissolution of pre-existing phases and concomitant precipitation of new ones (e.g. Putnis, 2002).…”

Section: Introductionmentioning

confidence: 99%

Metasomatism of gabbro - mineral replacement and element mobilization during the Sveconorwegian metamorphic event

Engvik¹,

Mezger

Wortelkamp

et al. 2010

Journal of Metamorphic Geology

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Widespread metasomatism affected the 100 km long and 25 km wide Proterozoic Bamble and ModumKongsberg sectors, South Norway, resulting in the chemical and mineralogical transformation of wide segments of continental crust. Scapolitization was associated with veining, and was followed by albitization, transforming metagabbros pervasively over large areas. Fluids played an active role in these reactions, forming H 2 O-, CO 2 -and Cl-bearing phases at the expense of the primary volatile-free minerals, causing depletion in Fe and infiltration of K, Mg, Na, B and P. The transformation of gabbro to scapolite metagabbro is observed as a fluid front replacing the primary magmatic mineral assemblage in three stages: during an incipient amphibolitization stage, the primary mafic minerals were replaced by anthophyllite or hastingsite, followed by pargasitic and edenitic Ca-amphibole. Magnetite was dissolved, while rutile formed by the breakdown of ilmenite. Plagioclase was replaced by Cl-rich scapolite (Me 19-42 ) reflecting Cl-saturation, while K-and Mg-saturation produced phlogopite, enstatite, sapphirine and rare corundum. The high modal contents of chlorapatite and tourmaline in the scapolite metagabbro imply infiltration of B and P. The albitites consist dominantly of albite (Ab 95-98 ) with varying, generally small, amounts of chlorite, calcite, rutile, epidote and pumpellyite. They formed from a H 2 O-CO 2 -fluid rich in Na. The gabbro yields a zircon U-Pb age of 1149 ± 7 Ma and tonalite 1294 ± 38 Ma, whereas rutile from scapolite metagabbro and albitite has U-Pb ages of 1090-1084 Ma, and phlogopite produced during scapolitization Rb-Sr ages of 1070-1040 Ma. Temperature conditions for the scapolitization are inferred to have been 600-700°C. The reported ages, combined with mineralogical and petrographic observations and inferred P-T conditions, indicate that the metasomatism was a part of the regional Sveconorwegian amphibolite facies metamorphic phase. Initial 87 Sr ⁄ 86 Sr of the scapolite ranges from 0.704 to 0.709. The Sr-signature, the Cl-and B-rich environment and regional distribution of lithologies suggest that the fluid may have originated from evaporites that were mobilized during the regional metamorphism.

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“…1530 Ma (D 4 : Oliver et al, 2004Oliver et al, , 2008 in conjunction with intrusion of the Mount Angelay and Saxby granites and involved alteration of feldspars to albite, pyroxenes, and amphiboles to actinolite, titanite, and magnetite. A full review of Na-Ca alteration is provided by Williams (1998Williams ( , 2001, Williams and Pollard (2001), and Oliver et al (2004Oliver et al ( , 2008. Na-Ca alteration is significant for this study because it is associated with the breccia that hosts mineralization within the Brumby Prospect.…”

Section: Alterationmentioning

confidence: 99%

Magnetic modeling of iron oxide copper-gold mineralization constrained by 3D multiscale integration of petrophysical and geochemical data: Cloncurry District, Australia

2013

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Magnetite-rich iron oxide copper-gold deposits (IOCGs) are geologically and geochemically complex and present major challenges to geophysical investigation. They often sit beneath significant cover, exhibit magnetic remanence, and suffer from self-demagnetization effects. Because remanence in magnetite-bearing drill core samples is commonly overprinted by drilling, in situ natural remanent magnetization is difficult to measure accurately, and thus IOCGs cannot be modeled definitively using geophysics alone. We examined structural controls on a magnetite-rich IOCG in northwest Queensland and the relationships between structure, alteration, Fe oxides, and mineralization at core to deposit scale. Magnetite within the deposit has a multidomain structure, and thus it would commonly have an in situ magnetization parallel to the earth's field. In contrast, pyrrhotite has a pseudosingle-domain structure and so it is the predominant carrier of stable remanence within the ore system. Geophysical lineament analyses are used to determine structural controls on mineralization, geophysical filters (e.g., analytic signal amplitude) are used to help define structural extent of the deposit, and basement geochemistry is used to map mineral footprints beneath cover. These techniques identified coincident anomalies at the intersection of north and northwest lineaments. Leapfrog™ interpolations of downhole magnetic susceptibility and Cu, Au, and Fe assay data were used to map the distribution of magnetite, copper, gold, and sulfur in 3D. The analysis revealed that Cu and Au mineralization were coupled with the magnetite net-vein architecture, but that Cu was locally enriched in the east-northeast-trending demagnetized zone. The results from this suite of geophysical, petrophysical, and geochemical techniques were integrated to constrain modeling of the Brumby IOCG. Brumby can be described as a breccia pipe sitting at the intersection of north-striking, east-dipping, and northwest-striking, southeast-dipping structures that plunges moderately to the south-southeast. The breccia pipe was overprinted by a relatively late net-vein magnetite breccia and crosscut by a later, magnetitedestructive, east-northeast-striking fault.

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Modeling the Role of Sodic Alteration in the Genesis of Iron Oxide-Copper-Gold Deposits, Eastern Mount Isa Block, Australia

Cited by 208 publications

References 58 publications

Granite‐related overpressure and volatile release in the mid crust: fluidized breccias from the Cloncurry District, Australia

Granite‐related overpressure and volatile release in the mid crust: fluidized breccias from the Cloncurry District, Australia

Metasomatism of gabbro - mineral replacement and element mobilization during the Sveconorwegian metamorphic event

Magnetic modeling of iron oxide copper-gold mineralization constrained by 3D multiscale integration of petrophysical and geochemical data: Cloncurry District, Australia

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