The Moruya Batholith and geochemical contrasts between the Moruya and Jindabyne suites

Griffin, T. J.; White, A. J. R.; Chappell, B. W.

doi:10.1080/00167617808729030

Cited by 93 publications

(39 citation statements)

References 17 publications

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“…The K/Ar hornblende date places the median age at mid-Frasnian on the time-scale of Gradstein, Ogg, Schmitz, and Ogg (2012). These dates are comparable with other onshore Moruya Suite rocks (Griffen, White, & Chappell, 1978). However, a UÀPb zircon age of 396.2 § 1.4 for the Tuross Pluton Ma quoted by Prendergast et al (2011) gives it a late Emsian age and is likely to be applicable to the granodiorite from this site.…”

Section: Australian Journal Of Earth Sciencesmentioning

confidence: 49%

The Narooma Terrane offshore: a new model for the southeastern Lachlan Orogen using data from rocks dredged from the New South Wales continental slope

Packham

Hubble

2016

Australian Journal of Earth Sciences

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Eight dredges from the southern New South Wales continental slope sampled the offshore extension of the Lachlan Orogen. Two rock suites were recovered: (1) lower greenshist facies limestones, felsic volcanics, sandstones, mudstones and Moruya Suite granodiorite correlate with the onshore Silurian to mid-Devonian orogenic phase; and (2) a strongly deformed greenschist to lower amphibolite facies mafic volcanics, cherts, marbles, pelites and serpentinites correlate in part with the CambroOrdovician Wagonga Group of the Narooma Terrane. The mafic volcanic rocks have ocean island, tholeiitic and boninitic basalt affinities. The offshore distribution of ocean island basalt that correlates with medial Cambrian basalt breccias at Batemans Bay suggests a large seamount or seamount complex. The boninites, tholeiites and ultramafics could be part of a forearc-generated ophiolite. The Narooma Terrane basement is interpreted as the part of the bonititic arc postulated to have collided with Vandieland in late early Cambrian time. Mid-Cambrian rifting of the oceanward part of this arc remnant, generated the AlburyÀBega Terrane oceanic basement exposed in the Howqua Valley in the west and Melville Point in the east. Overlying are upperÀmid-Cambrian to lowermost Ordovician black shale and chert, Lower Ordovician to Gisbornian Adaminaby Group quartz turbidites and Gisbornian to lower Bolindian Bendoc Group black shales. Batemans Bay exposures are reinterpreted as a dismembered basin margin succession onlapping the west-facing attenuated flank of the Narooma Terrane. The Narooma Cambro-Ordovician cherts and mudstones were initially deposited outboard on the more elevated seamount flank elevated above the clastic-filled basin to the west. Benambran deformation commenced in latest Ordovician time uplifting the outer Narooma Terrane, shedding debris from the seamount and its flanks, culminating in allochthonous displacement of chert masses to the basin's eastern margin to Narooma, and emplacing them as a succession of thrust sheets. Contemporaneously, silt and mud of the Bogolo Formation, deposited from the west, were mixed with olistostomal basalt and chert debris from the east. Early Silurian westward tectonic transport of the Narooma Terrane ruptured the Albury-Bega basin floor at Batemans Bay, thrusting it and its sedimentary cover over its eastern margin as a series of thrusts each floored by melange (mapped Bogolo Formation), derived from the slope debris and its overpressured sedimentary cover. Offshore, the metamorphosed Benambran phase rocks are unconformably overlain by Tabberabberan cycle sediments and volcanics intruded by granodiorite. Our interpretation of the boundary between the Albury-Bega and Narooma terranes as a thrusted passive margin accumulation is incompatible with models of a Narooma Accretionary Complex formed by the subduction of the Paleopacific Plate.

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Section: Australian Journal Of Earth Sciencesmentioning

confidence: 49%

The Narooma Terrane offshore: a new model for the southeastern Lachlan Orogen using data from rocks dredged from the New South Wales continental slope

Packham

Hubble

2016

Australian Journal of Earth Sciences

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“…The magma, or 'minimum melt' plus restite in this case, will initially have the same composition as that of the source material, and with fractionation of those two components, compositions between MM and either MD (I-type) or FS (S-type) will be produced. This is the situation with, for example, the I-type Moruya Suite (Griffin et al 1978), and apparently with all S-type suites in the LFB.…”

Section: Production Of Granite Magmas By Partial Melting Within the Cmentioning

confidence: 91%

I- and S-type granites in the Lachlan Fold Belt

Chappell

White²

1992

Earth and Environmental Science Transactions of the Royal Socie

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1,219

441

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Granites and related volcanic rocks of the Lachlan Fold Belt can be grouped into suites using chemical and petrographic data. The distinctive characteristics of suites reflect source-rock features. The first-order subdivision within the suites is between those derived from igneous and from sedimentary source rocks, the I- and S-types. Differences between the two types of source rocks and their derived granites are due to the sedimentary source material having been previously weathered at the Earth's surface. Chemically, the S-type granites are lower in Na, Ca, Sr and Fe3+/Fe2+, and higher in Cr and Ni. As a consequence, the S-types are always peraluminous and contain Al-rich minerals. A little over 50% of the I-type granites are metaluminous and these more mafic rocks contain hornblende. In the absence of associated mafic rocks, the more felsic and slightly peraluminous I-type granites may be difficult to distinguish from felsic S-type granites. This overlap in composition is to be expected and results from the restricted chemical composition of the lowest temperature felsic melts. The compositions of more mafic I- and S-type granites diverge, as a result of the incorporation of more mafic components from the source, either as restite or a component of higher temperature melt. There is no overlap in composition between the most mafic I- and S-type granites, whose compositions are closest to those of their respective source rocks. Likewise, the enclaves present in the more mafic granites have compositions reflecting those of their host rocks, and probably in most cases, the source rocks.S-type granites have higher δ18O values and more evolved Sr and Nd isotopic compositions, although the radiogenic isotope compositions overlap with I-types. Although the isotopic compositions lie close to a mixing curve, it is thought that the amount of mixing in the source rocks was restricted, and occurred prior to partial melting. I-type granites are thought to have been derived from deep crust formed by underplating and thus are infracrustal, in contrast to the supracrustal S-type source rocks.Crystallisation of feldspars from felsic granite melts leads to distinctive changes in the trace element compositions of more evolved I- and S-type granites. Most notably, P increases in abundance with fractionation of crystals from the more strongly peraluminous S-type felsic melts, while it decreases in abundance in the analogous, but weakly peraluminous, I-type melts.

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“…1). We here include also nine plutons of the Moruya Batholith (Griffin et al, 1978) and two I-type plutons of the Gabo Island Granites, which are located east of the Bega Batholith but have closely analogous compositional features. Except for the small Stanton Rock pluton (4 km 2 ) which may be S-type, and a restricted area of A-type granites (~150 km 2 ), the granites of this batholith are I-type and are arguably all of low-temperature origin according to the classification of .…”

Section: Bega Batholithmentioning

confidence: 98%

“…5). White and Chappell (1977), Griffin et al (1978), Chappell et al (1987) and Chappell (1996) have ascribed most of the chemical variations within suites of the Bega Batholith to differing degrees of separation of partial melt from its restite (i.e. the residuum of partial melting).…”

Section: Origins Of Compositional Variation Within Suites Of the Begamentioning

confidence: 98%

Peraluminous I-type granites

Chappell

Bryant

Wyborn³

2012

Lithos

421

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The Moruya Batholith and geochemical contrasts between the Moruya and Jindabyne suites

Cited by 93 publications

References 17 publications

The Narooma Terrane offshore: a new model for the southeastern Lachlan Orogen using data from rocks dredged from the New South Wales continental slope

The Narooma Terrane offshore: a new model for the southeastern Lachlan Orogen using data from rocks dredged from the New South Wales continental slope

I- and S-type granites in the Lachlan Fold Belt

Peraluminous I-type granites

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