Magmatic affinity of modern and ancient subalkaline volcanic rocks determined from trace-element discriminant diagrams

Ross, Pierre-Simon; Bédard, Jean H.

doi:10.1139/e09-054

Cited by 329 publications

(117 citation statements)

References 22 publications

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“…8). The source rocks have a calc-alkaline magmatic affinity according to the Zr-Y, La-Yb and Th-Yb diagrams of Ross and Bédard (2009;). The LREE enriched and flat HREE chondrite normalised REE patterns support this interpretation, as do the N-MORB normalised patterns because they show features characteristic of calcalkaline, continental arc rocks, namely, Nb, and Ta depletion, Zr and Hf < Nb and Ta, and high contents of Th (Pearce, 1983) (Figs.…”

Section: Geochemistrymentioning

confidence: 99%

Proto-Pacific-margin source for the Ordovician turbidite submarine fan, Lachlan Orogen, southeast Australia: Geochemical constraints

Offler

Fergusson

2016

Sedimentary Geology

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The Early Palaeozoic proto-Pacific Pacific margin of Gondwana was characterised by a huge turbidite submarine fan with abundant clastic detritus derived from unknown sources within Gondwana. These deposits are widespread in the Lachlan Orogen of southeast Australia and include the Ordovician Adaminaby Group. Here we show that the mudstones and sandstones of the Adaminaby Group have chemical compositions that indicate the detritus in them was derived from a felsic, continental source similar in composition to Post Archean Australian Shales (PAAS). Chondrite normalised REE patterns showing LREE enrichment, flat PAAS normalised patterns and elemental ratios La/Sc, Cr/Th, Cr/V, Th/Sc and Th/U, have been used to support this interpretation. The dominance of quartz, and to a lesser degree plagioclase and biotite in the sandstones, suggests that the source was mainly granodioritic to tonalitic in composition. Th/Yb and Ta/Yb ratios indicate that the source was probably calc-alkaline, continental and shoshonitic. In addition, the presence of detrital muscovite, low-grade metamorphic and felsic volcanic clasts, demonstrates that a lowgrade metamorphic terrane and volcanic arc contributed to the detritus observed in the samples. The presence of well-rounded zircons and tourmalines, very high Zr contents, high Zr/Sc and higher Cr/V ratios in some samples particularly in the Shoalhaven River area, indicate that some of the detritus was recycled.SiO2 versus (Al2O3 + K2O + Na2O) plots suggest the source areas experienced conditions varying from humid/semihumid to semi-arid. Textural features and weathering trends of samples from all locations follow a curved pathway on Al2O3 -(CaO* + Na2O) -K2O (ACNK) diagrams, and indicate that the clays formed from weathering had been K-metasomatised prior to penetrative deformation. Chemical indices of alteration (CIA) reveal that even the freshest sandstones are altered and others are moderately to strongly altered. Discrimination diagrams involving major, trace and REE strongly support a collisional/continental volcanic arc setting that was substantially eroded to produce the plutonic detritus observed in the sandstones. The collisional setting accords with that proposed previously by other authors who suggested that it developed during the Delamerian Orogeny, resulting in the uplifted source areas providing detritus that inundated the backarc and forearc sites of the Macquarie Arc. Some of the detritus, however, may have been derived from a continental arc that existed in the late Cambrian along the margin of the Ross Orogen. Based on palaeocurrent analyses in previous studies and shoshonitic signature of the detritus, it is proposed that the Cambrian volcanics along the eastern active margin of Gondwana provided much of the detritus in the Adaminaby Group. Zircons with the Grenvillian signature suggest that some detritus were also derived from the Ross Orogen. Discrimination diagrams involving major, trace and REE strongly support a collisional/continental volcanic arc setting...

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Section: Geochemistrymentioning

confidence: 99%

Proto-Pacific-margin source for the Ordovician turbidite submarine fan, Lachlan Orogen, southeast Australia: Geochemical constraints

Offler

Fergusson

2016

Sedimentary Geology

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“…Most rocks fall within the tholeiitic field of Ross and Bedard (2009) (Fig. 7b) 448 with rocks from sequences 1, 2, 3 I , 4, and the mafic intrusions defining a cluster with 449 Zr/Y ratios ranging from 1.9 to 5.3, and dacitic rocks from sequence 3 F defining another 450 cluster with higher Zr/Y ratios ranging from 3.2 to 5.5.…”

Section: Immobile Element Systematics 447mentioning

confidence: 98%

Lithostratigraphic and structural reconstruction of the Zn-Pb-Cu-Ag-Au Lemarchant volcanogenic massive sulphide (VMS) deposit, Tally Pond group, central Newfoundland, Canada

Cloutier

Piercey

Lode

et al. 2017

Ore Geology Reviews

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“…The Zr/Y ratio is a proxy for magmatic affinity (Barrett and MacLean, 1999;Ross and Bédard, 2009). On a Zr versus Y diagram (Fig.…”

Section: Characterizing Lithologies and Locating Geological Contactsmentioning

confidence: 99%

High-Resolution Physical Properties, Geochemistry, and Alteration Mineralogy for the Host Rocks of the Archean Lemoine Auriferous Volcanogenic Massive Sulfide Deposit, Canada

et al. 2016

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Multi-parameter data on drill cores has a range of useful applications for ore deposit modeling and mineral exploration. Density, magnetic susceptibility, eight major elements, seven trace elements (portable X-ray fluorescence, pXRF), five mineral groups (near-infrared spectrometry) and average visible light reflectance were determined on rock cores from several drill holes. These are located near the Archean Lemoine auriferous volcanogenic massive sulfide (VMS) deposit in the Chibougamau mining district, Abitibi Subprovince, Quebec, Canada. This case study focuses on one drill hole in particular which has been recently characterized in detail by conventional methods (laboratory geochemistry, petrography, stable isotopes); this provides validation for the multi-sensor dataset. The best variables and immobile element ratios to distinguish between different lithological units in the multi-parameter data are density, magnetic susceptibility, Ti/Zr, Al/Zr, and Zr/Y. Downhole profiles of these parameters allow the four different felsic units in LEM-37, many of which are visually similar, to be distinguished, and geological contacts to be positioned precisely. Such methods would be even more useful in environments where recognition of primary characteristics is strongly hampered by intense hydrothermal alteration and superimposed deformation or metamorphism. Volcanic and intrusive rocks can be placed on classic diagrams to assign them names and magmatic affinities based on the corrected pXRF data. Downhole profiles of major and trace elements, combined with infrared mineralogy, allow hydrothermal alteration to be characterized, yielding results comparable to those of conventional techniques for the same drill hole, but with a much tighter spacing and within potentially shorter timeframes.

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Magmatic affinity of modern and ancient subalkaline volcanic rocks determined from trace-element discriminant diagrams

Cited by 329 publications

References 22 publications

Proto-Pacific-margin source for the Ordovician turbidite submarine fan, Lachlan Orogen, southeast Australia: Geochemical constraints

Proto-Pacific-margin source for the Ordovician turbidite submarine fan, Lachlan Orogen, southeast Australia: Geochemical constraints

Lithostratigraphic and structural reconstruction of the Zn-Pb-Cu-Ag-Au Lemarchant volcanogenic massive sulphide (VMS) deposit, Tally Pond group, central Newfoundland, Canada

High-Resolution Physical Properties, Geochemistry, and Alteration Mineralogy for the Host Rocks of the Archean Lemoine Auriferous Volcanogenic Massive Sulfide Deposit, Canada

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