Trace element partitioning in the granulite facies

Nehring, Franziska; Foley, Stephen F.; Hölttä, Pentti

doi:10.1007/s00410-009-0437-y

Cited by 55 publications

(22 citation statements)

References 102 publications

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“…b Melting of a garnet-free two-pyroxene source with approximate modal compositions from Bradley (1985); 50 % plagioclase, 20 % orthopyroxene, 24 % clinopyroxene, 4 % amphibole, 2 % apatite product of alkali feldspar fractionation during shallow differentiation. This conclusion is consistent with the fact that even 10 % partial melting (not shown) of typical State Line two-pyroxene granulite xenoliths only generates melts with modest negative Eu anomalies (Eu/Eu* ≥ 0.9) and leaves a residual solid with Eu/Eu* of only 1.05-1.08, using mineral-melt partition coefficients from Nehring et al (2009). Although high Eu/Eu* feldspars must have accumulated somewhere within the crust, such a chemical signature was not likely imparted to the restite remaining after the original mafic lower crust melted.…”

Section: Discussionsupporting

confidence: 85%

“…13). Rare earth element, Sr, and Y mineral-melt partition coefficients used were those estimated by Bédard (2006) and Nehring et al (2009) for the anatexis of mafic granulites (see Supplementary Material). The average source rock trace element abundances used were those from the "high La/Yb N " State Line diatreme xenoliths (Farmer et al 2005), and the range of mineral modes for these xenoliths were from Bradley (1985).…”

Section: Discussionmentioning

confidence: 99%

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Deep crustal anatexis, magma mixing, and the generation of epizonal plutons in the Southern Rocky Mountains, Colorado

Jacob

Farmer

Buchwaldt

et al. 2015

Contrib Mineral Petrol

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differentiated versions of the silicic melts parental to the Mt. Cumulus stock. Zircon U-Pb geochronology further reveals that the Mt. Richthofen stock was incrementally emplaced over a time interval from at least 28.975 ± 0.020 to 28.742 ± 0.053 Ma. Magma mixing could have occurred either in situ in the upper crust during basaltic underplating and remelting of an antecedent, incrementally emplaced, silicic intrusive body, or at depth in the lower crust prior to periodic magma ascent and emplacement in the shallow crust. Overall, the two stocks demonstrate that magmatism associated with the Never Summer igneous complex was fundamentally bimodal in composition. Highly silicic anatectic melts of the mafic lower crust and basaltic, mantle-derived magmas were the primary melts in the magma system, with mixing of the two producing intermediate composition magmas such as those from which Mt. Richthofen stock was constructed.

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Section: Discussionsupporting

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Deep crustal anatexis, magma mixing, and the generation of epizonal plutons in the Southern Rocky Mountains, Colorado

Jacob

Farmer

Buchwaldt

et al. 2015

Contrib Mineral Petrol

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“…They are also a potentially important source of H 2 O, F and Cl. Another important repository, in granulite facies rocks, for Nb and Ta is ilmenite (Nehring et al, 2010). In metapelite melting, these characteristic elements of rare-metal granites will typically partition into the melt (Icenhower and London, 1995).…”

Section: Sources Of Pegmatitesmentioning

confidence: 99%

Petrogenesis of rare-metal pegmatites in high-grade metamorphic terranes: a case study from the Lewisian Gneiss Complex of north-west Scotland

Shaw

Goodenough

Horstwood³

et al. 2016

Applied Earth Science

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a b s t r a c tMany rare metals used today are derived from granitic pegmatites, but debate continues about the origin of these rocks. It is clear that some pegmatites represent the most highly fractionated products of a parental granite body, whilst others have formed by anatexis of local crust. However, the importance of these two processes in the formation of rare-metal pegmatites is not always evident.The Lewisian Gneiss Complex of NW Scotland comprises Archaean meta-igneous gneisses which were highly reworked during accretional and collisional events in the Palaeoproterozoic (Laxfordian orogeny). Crustal thickening and subsequent decompression led to melting and the formation of abundant granitic and pegmatitic sheets in many parts of the Lewisian Gneiss Complex. This paper presents new petrological, geochemical and age data for those pegmatites and shows that, whilst the majority are barren biotite-magnetite granitic pegmatites, a few muscovite-garnet (rare-metal) pegmatites are present. These are mainly intruded into a belt of Palaeoproterozoic metasedimentary and meta-igneous rocks known as the Harris Granulite Belt.The rare-metal pegmatites are distinct in their mineralogy, containing garnet and muscovite, with local tourmaline and a range of accessory minerals including columbite and tantalite. In contrast, the biotitemagnetite pegmatites have biotite and magnetite as their main mafic components. The rare-metal pegmatites are also distinguished by their bulk-rock and mineral chemistry, including a more peraluminous character and enrichments in Rb, Li, Cs, Be, Nb and Ta. New U-Pb ages (c. 1690-1710 Ma) suggest that these rare-metal pegmatites are within the age range of nearby biotite-magnetite pegmatites, indicating that similar genetic processes could have been responsible for their formation.The peraluminous nature of the rare-metal pegmatites strongly points towards a metasedimentary source. Notably, within the Lewisian Gneiss Complex, such pegmatites are only found in areas where a metasedimentary source is available. The evidence thus points towards all the Laxfordian pegmatites being formed by a process of crustal anatexis, with the formation of rare-metal pegmatites being largely controlled by source composition rather than solely by genetic process. This is in keeping with previous studies that have also challenged the widely accepted model that all rare-metal pegmatites are formed by fractionation from a parental granite, and raises questions about the origin of other mineralised pegmatites worldwide.

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“…Gahnite in metamorphosed alteration zones associated with VMS deposits is commonly intergrown with a variety of ferromagnesian silicates (e.g., amphiboles, biotite, garnet), sulfides (e.g., sphalerite, pyrrhotite), and oxides (e.g., magnetite, ilmenite). Therefore, it is likely that the trace element content of gahnite will also be variable and may be a function of partition of trace elements between coexisting phases, because coexisting silicates and oxides can accommodate transition metals (e.g., Nehring et al, 2010).…”

Section: Discussionmentioning

confidence: 99%

“…They noted that variability in the trace element composition of gahnite was a function of different physicochemical conditions during gahnite growth, whole-rock geochemistry, pre-metamorphic alteration, and the chemistry of precursor minerals. Like other members of the spinel group (e.g., magnetite and chromite), the trace element chemistry of gahnite is dominated by the first series transition metals (i.e., Ti, V, Cr, Mn, Co, Ni), Ga, and Cd (Dupuis and Beaudoin, 2011;Nadoll et al, 2012;Nehring et al, 2010;Pagé and Barnes, 2009). No trace element compositions of gahnite from other metamorphosed massive sulfide deposits (e.g., SEDEX, VMS, and non-sulfide zinc (NSZ) deposits) have previously been obtained.…”

Section: Introductionmentioning

confidence: 99%

Gahnite composition as a means to fingerprint metamorphosed massive sulfide and non-sulfide zinc deposits

O'Brien

Spry

Teale³

et al. 2015

Journal of Geochemical Exploration

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Gahnite occurs in and around metamorphosed massive sulfide (e.g., Broken Hill-type Pb-Zn-Ag (BHT), volcanogenic massive sulfide Cu-Zn-Pb-Au-Ag (VMS), sedimentary exhalative Pb-Zn (SEDEX)), and nonsulfide zinc (NSZ) deposits. In addition to occurring in situ, gahnite occurs as a resistate indicator mineral in unconsolidated sediments (e.g., glacial till) surrounding such deposits. The spatial association between gahnite and metamorphosed ore deposits has resulted in its use as an empirical exploration guide to ore. Major and trace element compositions of gahnite from BHT, NSZ, SEDEX, and VMS deposits are used here to develop geochemical fingerprints for each deposit type. A classification tree diagram, using a combination of six discrimination plots, is presented here to identify the provenance of detrital gahnite in greenfield and brownfield terranes, which can be used as an exploration guide to metamorphosed massive sulfide and nonsulfide zinc deposits. The composition of gahnite in BHT deposits is discriminated from gahnite in SEDEX and VMS deposits on the basis of plots of Mg versus V, and Co versus V. Gahnite in SEDEX deposits can be distinguished from that in VMS deposits using plots of Co versus V, Mn versus Ti, and Co versus Ti. In the Sterling Hill NSZ deposit, gahnite contains higher concentrations of Fe3+ and Cd, and lower amounts of Al, Mg, and Co than gahnite in BHT, SEDEX, and VMS deposits. Plots of Co versus Cd, and Al versus Mg distinguish gahnite in the Sterling Hill NSZ deposit from the other types of deposits. Gahnite occurs in and around metamorphosed massive sulfide (e.g., Broken Hill-type Pb-Zn-Ag (BHT), volcanogenic massive sulfide Cu-Zn-Pb-Au-Ag (VMS), sedimentary exhalative Pb-Zn (SEDEX)), and nonsulfide zinc (NSZ) deposits. In addition to occurring in situ, gahnite occurs as a resistate indicator mineral in unconsolidated sediments (e.g., glacial till) surrounding such deposits. The spatial association between gahnite and metamorphosed ore deposits has resulted in its use as an empirical exploration guide to ore. Major and trace element compositions of gahnite from BHT, NSZ, SEDEX, and VMS deposits are used here to develop geochemical fingerprints for each deposit type. A classification tree diagram, using a combination of six discrimination plots, is presented here to identify the provenance of detrital gahnite in greenfield and brownfield terranes, which can be used as an exploration guide to metamorphosed massive sulfide and non-sulfide zinc deposits. The composition of gahnite in BHT deposits is discriminated from gahnite in SEDEX and VMS deposits on the basis of plots of Mg versus V, and Co versus V. Gahnite in SEDEX deposits can be distinguished from that in VMS deposits using plots of Co versus V, Mn versus Ti, and Co versus Ti. In the Sterling Hill NSZ deposit, gahnite contains higher concentrations of Fe 3+ and Cd, and lower amounts of Al, Mg, and Co than gahnite in BHT, SEDEX, and VMS deposits. Plots of Co versus Cd, and Al versus Mg distinguish gahnite in the Sterlin...

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Trace element partitioning in the granulite facies

Cited by 55 publications

References 102 publications

Deep crustal anatexis, magma mixing, and the generation of epizonal plutons in the Southern Rocky Mountains, Colorado

Deep crustal anatexis, magma mixing, and the generation of epizonal plutons in the Southern Rocky Mountains, Colorado

Petrogenesis of rare-metal pegmatites in high-grade metamorphic terranes: a case study from the Lewisian Gneiss Complex of north-west Scotland

Gahnite composition as a means to fingerprint metamorphosed massive sulfide and non-sulfide zinc deposits

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