Chapter 30: Geologic Evolution of Late Ordovician to Early Silurian Alkalic Porphyry Au-Cu Deposits at Cadia, New South Wales, Australia

2020 ◽  
pp. 621-643
Author(s):  
Anthony C. Harris ◽  
David R. Cooke ◽  
Ana Liza Garcia Cuison ◽  
Malissa Groome ◽  
Alan J. Wilson ◽  
...  
Keyword(s):  
New South ◽  
New South Wales ◽  
Ore Deposits ◽  
Late Ordovician ◽  
Intrusive Complex ◽  
Potassic Alteration ◽  
South Wales ◽  
Propylitic Alteration ◽  
Volcaniclastic Rocks

Abstract The Cadia district of New South Wales contains four alkalic porphyry Au-Cu deposits (Cadia East, Ridgeway, Cadia Hill, and Cadia Quarry) and two Cu-Au-Fe skarn prospects (Big Cadia and Little Cadia), with a total of ~50 Moz Au and ~9.5 Mt Cu (reserves, resources, and past production). The ore deposits are hosted by volcaniclastic rocks of the Weemalla Formation and Forest Reefs Volcanics, which were deposited in a submarine basin on the flanks of the Macquarie Arc during the Middle to Late Ordovician. Alkalic magmatism occurred during the Benambran orogeny in the Late Ordovician to early Silurian, resulting in the emplacement of monzonite intrusive complexes and the formation of porphyry Au-Cu mineralization. Ridgeway formed synchronous with the first compressive peak of deformation and is characterized by an intrusion-centered quartz-magnetite-bornite-chalcopyrite-Au vein stockwork associated with calc-potassic alteration localized around the apex of the pencil-like Ridgeway intrusive complex. The volcanic-hosted giant Cadia East deposit and the intrusion-hosted Cadia Hill and Cadia Quarry deposits formed during a period of relaxation after the first compressive peak of the Benambran orogeny and are characterized by sheeted quartz-sulfide-carbonate vein arrays associated with subtle potassic, calc-potassic, and propylitic alteration halos.

Chlorite and Epidote Mineral Chemistry in Porphyry Ore Systems: A Case Study of the Northparkes District, New South Wales, Australia

2020 ◽  
Vol 115 (4) ◽  
pp. 701-727 ◽  
Author(s):  
Adam Pacey ◽  
Jamie J. Wilkinson ◽  
David R. Cooke
Keyword(s):  
New South ◽  
New South Wales ◽  
Mineral Chemistry ◽  
Ore Deposits ◽  
Low Grade ◽  
South Wales ◽  
Spatial Trends ◽  
Propylitic Alteration ◽  
Mineral Partitioning

Abstract Propylitic alteration, characterized by the occurrence of chlorite and epidote, is typically the most extensive and peripheral alteration facies developed around porphyry ore deposits. However, exploration within this alteration domain is particularly challenging, commonly owing to weak or nonexistent whole-rock geochemical gradients and the fact that similar assemblages can be developed in other geologic settings, particularly during low-grade metamorphism. We document and interpret systematic spatial trends in the chemistry of chlorite and epidote from propylitic alteration around the E48 and E26 porphyry Cu-Au deposits of the Northparkes district, New South Wales, Australia. These trends vary as a function of both distance from hydrothermal centers and alteration paragenesis. The spatial trends identified in porphyry-related chlorite and epidote at Northparkes include (1) a deposit-proximal increase in Ti, As, Sb, and V in epidote and Ti in chlorite, (2) a deposit-distal increase in Co and Li in chlorite and Ba in epidote, and (3) a pronounced halo around deposits in which Mn and Zn in chlorite, as well as Mn, Zn, Pb, and Mg in epidote, are elevated. Chlorite Al/Si ratios and epidote Al/Fe ratios may show behavior similar to that of Mn-Zn or may simply decrease outward, and V and Ni concentrations in chlorite are lowest in the peak Mn-Zn zone. In comparison to porphyry-related samples, chlorite from the regional metamorphic assemblage in the district contains far higher concentrations of Li, Ca, Ba, Pb, and Cu but much less Ti. Similarly, metamorphic epidote contains higher concentrations of Sr, Pb, As, and Sb but less Bi and Ti. These chlorite and epidote compositional trends are the net result of fluid-mineral partitioning under variable physicochemical conditions within a porphyry magmatic-hydrothermal system. They are most easily explained by the contribution of spent magmatic-derived ore fluid(s) into the propylitic domain. It is envisaged that such fluids experience progressive cooling and reduction in fs2 during outward infiltration into surrounding country rocks, with their pH controlled by the extent of rock-buffering experienced along the fluid pathway.

The first well-preserved radiolarians from the Ordovician of Australia

1986 ◽  
Vol 60 (1) ◽  
pp. 145-157 ◽  
Author(s):  
B. D. Webby ◽  
W. M. Blom
Keyword(s):  
New Species ◽  
Debris Flows ◽  
New South ◽  
New South Wales ◽  
Late Ordovician ◽  
Siliceous Sponge ◽  
Radiolarian Assemblage ◽  
South Wales ◽  
Limestone Breccia

Late Ordovician radiolarians are described from allochthonous limestone breccia deposits of the graptolitic Malongulli Formation of central New South Wales. Included among the forms are the new ‘palaeoactinommid’ genus Kalimnasphaera with new species K. maculosa, the new entactiniid species, Entactinia subulata, and the new anakrusid species, Auliela taplowensis. A number of other entactiniids and the first recorded Ordovician ‘rotasphaerids’ are placed in open nomenclature. Graptolite faunas of the Malongulli Formation indicate that the deposits range in age from the Eastonian Zone of Dicranograptus hians kirki to the Bolindian Zone of Climacograptus uncinatus, that is, from latest Caradoc to early or middle Ashgill in age. This is only the second known well-preserved radiolarian assemblage to be illustrated from Late Ordovician (late Caradoc–Ashgill) successions, and the earliest known from Australia. The radiolarians typically occur in tabularly shaped, laminated lime-mudstone clasts with an abundance of siliceous sponge remains. These clasts appear to be formed from peri-platform ooze of the ‘deeper-water’ slope facies, which became incorporated in debris flows moving into the adjoining basin.

Middle and Late Ordovician magmatic evolution of the Macquarie Arc, Lachlan Orogen, New South Wales

2007 ◽  
Vol 54 (2-3) ◽  
pp. 181-214 ◽  
Author(s):  
A. J. Crawford ◽  
S. Meffre ◽  
R. J. Squire ◽  
L. M. Barron ◽  
T. J. Falloon
Keyword(s):  
New South ◽  
New South Wales ◽  
Late Ordovician ◽  
Magmatic Evolution ◽  
South Wales ◽  
Lachlan Orogen

Late Ordovician nautiloids from central New South Wales, Australia

1985 ◽  
Vol 9 (2) ◽  
pp. 143-157 ◽  
Author(s):  
Bryan Stait ◽  
Barry D. Webby ◽  
Ian G. Percival
Keyword(s):  
New South ◽  
New South Wales ◽  
Late Ordovician ◽  
South Wales

Trilobites of the suborder Illaenina from the Silurian of north Queensland, Australia

2016 ◽  
Vol 90 (3) ◽  
pp. 433-471 ◽  
Author(s):  
David J. Holloway ◽  
Philip D. Lane
Keyword(s):  
New South ◽  
New South Wales ◽  
Late Ordovician ◽  
Junior Synonym ◽  
South Wales ◽  
Senior Synonym

AbstractThe trilobite fauna of the middle Silurian (Telychian to possibly earliest Sheinwoodian) Tomcat Creek limestone in the Broken River Province of north Queensland is dominated by the suborder Illaenina, including illaenimorphs (Illaeninae and Bumastinae) and members of the Scutelluidae. Scutelluidae are most diverse, with eight genera, of whichDolabrapex,Iotoryx,Perizostra, andQuintoniaare new.Perizostrais the first scutelluid with a cephalon that may be described as of phacomorph appearance. Illaenimorphs are represented by three genera, includingOpsypharus, which is regarded as a senior synonym ofParacybantyxbut distinct fromFailleanawith which it has been placed in synonymy by some authors. Thirteen species are new:Cybantyx?ergodes,Opsypharus pandanensis,Australoscutellum talenti,Dolabrapex acomus,Illaenoscutellum psephos,Iotoryx clarksoni,Japonoscutellum mawsonae,J. drakton,J. fractum,Kosovopeltis avita,Perizostra campbelli,Quintonia arata, andQ. pavo. A species ofStenopariais placed in open nomenclature. The species ofAustraloscutellum,Illaenoscutellum, and possiblyKosovopeltisare the oldest known representatives of those genera. These genera andJaponoscutellumare also common in faunas from limestones of Wenlock to Ludlow age in central western New South Wales, reflecting the similarity in lithofacies. The monotypic Late Ordovician genusCraigheadia, which has been regarded as a scutelluid, belongs to the Lichidae and is probably a junior synonym ofLeiolichas.

An occurrence of todorokite in the deuteric stage of a basalt

1968 ◽  
Vol 36 (282) ◽  
pp. 757-760 ◽  
Author(s):  
L. J. Lawrence ◽  
P. Bayliss ◽  
Paul Tonkin
Keyword(s):  
Base Metal ◽  
New South ◽  
New South Wales ◽  
Ore Deposits ◽  
South Wales ◽  
Tertiary Basalt

SummaryAn occurrence of todorokite having a formula is recorded from Ardglen, 150 miles N.N.W. of Sydney, New South Wales. The composition of Ardglen todorokite is somewhat simpler than previously recorded occurrences, most of which were in manganese and manganese—base-metal ore deposits. The simpler composition is explained in terms of its occurrence as a late deuteric mineral associated with manganocalcite and zeolites in an altered Tertiary basalt. The manganese is believed to have been derived from the deuteric alteration of the augite of the basalt.

Significance of clinopyroxene compositions from the Cudgegong Volcanics and Toolamanang Volcanics: Cudgegong-Mudgee district, NSW, Australia

1985 ◽  
Vol 49 (353) ◽  
pp. 591-599 ◽  
Author(s):  
J. W. Pemberton ◽  
R. Offler
Keyword(s):  
New South ◽  
New South Wales ◽  
Structural Formula ◽  
Primary Phase ◽  
Late Ordovician ◽  
Parent Magma ◽  
Calc Alkaline ◽  
South Wales ◽  
Stratigraphic Position ◽  
Altered Basalt

SynopisClinopyroxene phenocrysts and groundmass crystals are relict phases in altered basalt and basaltic andesite lavas, and arenites of the Cudgegong Volcanics and Toolamanang Volcanics, Cudgegong-Mudgee district, New South Wales. Petrography, field relationships and clinopyroxene compositions indicate that basaltic blocks in the latter unit are reworked from the Cudgegong Volcanics. Clinopyroxene phenocrysts show a restricted compositional range and minor Feenrichment from core to rim, features considered indicative of a calc-alkaline parent magma. It is proposed that the Cudgegong Volcanics crystallized under hydrous conditions, at least in the later stages, with rising fO2 resulting in a Fe-Ti oxide crystallizing as a primary phase. The clinopyroxenes are considered to have crystallized at moderate (5–6 kbar) and falling pressures and at minimum temperatures in the range 900 to 1000°C. Coupled substitutions affecting the “other” components in the clinopyroxene structural formula indicate that the ivAl-viFe3+, ivAl-viAl and ivAl-viTi4+ couples are important. The Sofala Volcanics, south of the study area, and the Cudgegong Volcanics are similar in age, petrography and stratigraphic position, and contain relict clinopyroxenes which are chemically similar. This suggests that the units are laterally equivalent and adds further evidence to the proposal that an oceanic island arc system was active in central western New South Wales during the Late Ordovician.

Ordovician sponge spicules from New South Wales, Australia

1993 ◽  
Vol 67 (1) ◽  
pp. 28-41 ◽  
Author(s):  
B. D. Webby ◽  
J. Trotter
Keyword(s):  
Debris Flows ◽  
New South ◽  
New South Wales ◽  
Late Ordovician ◽  
New Genera ◽  
Siliceous Sponge ◽  
Upper Cambrian ◽  
South Wales ◽  
Sponge Spicules ◽  
First Time

An abundant, varied, and well-preserved assemblage of discrete sponge spicules of late Ordovician age is described from the Malongulli Formation of central New South Wales. It is associated with one of the most diverse Ordovician siliceous sponge faunas known. The assemblage occurs in allochthonous limestone blocks within breccia deposits of a predominantly graptolitic and spiculitic siltstone succession, and is composed mainly of hexactinellid spicule types. Included are a number of distinctive forms, recognized as new taxa—Silicunculus bengtsoni, Kometia cruciformis, Chelispongia prima, and Pseudolancicula exigua. All are new genera except Silicunculus Bengtson, 1986, which was previously described from the upper Cambrian of Queensland. The problematical Anomaloides reticulatus Ulrich, 1878, is reported for the first time from Australia. A wide variety of other diagnostic, but more generalized, spicule types also occurs, including stauractines, pinnular and nonpinnular pentactines and hexactines, ornamented oxyhexasters and echinhexasters, clavules, anchorate root-tufts, and uncinates. The pinnular pentactines may be assigned to the form genus Palaeorubus Ishiga (in Ishiga et al., 1987), interpreted incorrectly by Ishiga as a radiolarian. The sponges, discrete spicules, and radiolarians of these limestone clasts were transported in debris flows to a basinal setting from peri-platform oozes that formed on the flanks of the shallow offshore island-arc platform of the Molong High.

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