Experimental silicate mineral/melt partition coefficients for beryllium and the crustal Be cycle from migmatite to pegmatite

Evensen, Joseph M.; London, David

doi:10.1016/s0016-7037(02)00889-x

Cited by 81 publications

(37 citation statements)

References 46 publications

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“…The occurrence of both minerals implies that these pegmatites are late‐stage differentiates (e.g. Miller & Stoddard, 1981; Evenson & London, 2002), and not small volume, in situ partial melts. However, while ASO‐age granites have been intersected in drill cores through correlatives of the Amadeus Basin, to the SE of the Eastern Arunta Region (the Warburton Basin, Gatehouse et al.…”

Section: Discussionmentioning

confidence: 97%

Timing relationships between pegmatite emplacement, metamorphism and deformation during the intra‐plate Alice Springs Orogeny, central Australia

Buick

Storkey

Williams³

2008

Journal Metamorphic Geology

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In the Harts Range (central Australia), the upper amphibolite facies to lower granulite facies, c. 480-460 Ma Harts Range Metamorphic Complex (HRMC), and the upper amphibolite facies, c. 340-320 Ma Entia Gneiss Complex are cut by numerous, generally peraluminous pegmatites and their deformed equivalents. The pegmatites have previously been interpreted as locally derived partial melts. However, SHRIMP U-Pb monazite and zircon dating of 29 pegmatites or their deformed equivalents, predominantly from the HRMC, reveal that they were emplaced episodically throughout almost the entire duration of the polyphase, c. 450-300 Ma intra-plate Alice Springs Orogeny. Episodes of pegmatite intrusion correlate with the age of major Alice Springs-age structures and with deposition of syn-orogenic sedimentary rocks in the adjacent Centralian Superbasin. Similar Alice Springs ages have not been obtained from anatectic country rocks in the HRMC, suggesting that the pegmatites were not locally derived. Instead, they are interpreted as highly fractionated granites, and imply that much larger parental Alice Springs-age granites exist at depth. The mechanism to allow repeated felsic magmatism in an intraplate setting, where all exposed rock types had a previous high-temperature history, is enigmatic. However, we suggest that episodic underthrusting and dehydration of unmetamorphosed Centralian Superbasin sedimentary rocks allowed crustal fertility to maintained over a c. 140 Ma interval during the intra-plate Alice Springs Orogeny.

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Section: Discussionmentioning

confidence: 97%

Timing relationships between pegmatite emplacement, metamorphism and deformation during the intra‐plate Alice Springs Orogeny, central Australia

Buick

Storkey

Williams³

2008

Journal Metamorphic Geology

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“…The crystal chemistry of Be dominates its geological fate. Evensen and London (2002) summarized the principal crystal-chemical factors controlling the crustal distribution of Be as: (i) small ionic radius (0.27Å; Shannon & Prewitt, 1969;Shannon, 1976); (ii) mixed electron orbital configurations (e.g. Bader et al, 1967) that give rise to appreciable covalency; and (iii) a charge density (i.e.…”

Section: Evolution Of Be-bearing Granitoidsmentioning

confidence: 99%

Mineralogical and Geochemical Characterization of Beryl‐Bearing Granitoids, Eastern Desert, Egypt: Metallogenic and Exploration Constraints

Abdalla

2009

Resource Geology

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Mineral chemistry and geochemical characteristics of beryl-bearing granitoids in Eastern Desert of Egypt, were examined in order to identify the metallogenetic processes of the host granitoids. The investigated Be-bearing granitoids and type occurrences are classified into two groups: (i) peraluminous, Ta Ն Nb + Sn + Be Ϯ W-enriched, Li-albite granite (e.g. Nuweibi and Abu Dabbab); and (ii) metasomatized, Nb >> Ta + Sn + Be Ϯ W Ϯ Mo-enriched alkali feldspar granite (i.e. apogranite; e.g. Homr Akarem, Homr Mikpid and Qash Amir). In these two groups, beryl occurs as stockwork greisen veins, greisen bodies, beryl-bearing cassiterite Ϯ wolframite quartz veins, dissemination, and miarolitic pegmatites. Beryl of the Be-granitoids, particularly those of miarolitic pegmatites, contains appreciable contents of Fe, Na, and H2O. An important feature of the Be-apogranites is the occurrence of white mica as the sole mafic mineral in the unaltered alkali feldspar granite in lower zones. Presence of white mica as volatile-rich pockets suggests that the melt underwent disequilibrium crystallization, rapid nucleation rates, and exsolving and expulsion of volatiles.

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“…Cerny et al, 2005;London, 2005). Pegmatites may also be generated during anatexis associated with regional metamorphism, but the presence of minerals such as beryl in rare-element pegmatites is thought to require extended crystal fractionation from a parent granite (Evensen & London, 2002). A mineralogical and chemical study of some of the rare-element pegmatites in this belt indicates that none of the granites in the area, including the leucocratic plutons constrained here to be Neoproterozoic in age, could have acted as sources of the pegmatites (Trautman, 1992).…”

Section: Timing Of Metamorphism and Granite-pegmatite Intrusionmentioning

confidence: 99%

Grenvillian‐aged orogenesis in the Palaeoproterozoic Gascoyne Complex, Western Australia: 1030–950 Ma reworking of the Proterozoic Capricorn Orogen

Sheppard

Rasmussen

Muhling

et al. 2007

Journal Metamorphic Geology

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In situ SHRIMP U-Pb geochronology of monazite and xenotime in pelitic schists from the central Gascoyne Complex, Western Australia, shows that greenschist to amphibolite facies metamorphism occurred between c. 1030 and c. 990 Ma. Monazite from an undeformed rare-element pegmatite from the same belt gives a 207 Pb/ 206 Pb age of c. 950 Ma, suggesting that peak metamorphism and deformation was followed by pegmatite intrusion and coeval granite magmatism. Metamorphism in the central Gascoyne Complex was previously interpreted as Barrovian, largely based on the identification of kyanite in peak metamorphic assemblages, and has been attributed to intense crustal shortening and substantial tectonic thickening during Palaeoproterozoic continent-continent collision. However, the stable Al 2 SiO 5 polymorph has been identified in this study as andalusite rather than kyanite, and the prograde assemblages of staurolite-garnet-andalusite-biotite-muscovite-quartz indicate temperatures of 500-550°C and pressures of 3-4 kbar. These data show that the Palaeoproterozoic Gascoyne Complex underwent an episode of Grenvillian-aged intracontinental reworking concentrated in a NW-SE striking corridor, during the Edmundian Orogeny. Until now, the Edmundian Orogeny was thought to have involved only reactivation of structures in the Gascoyne Complex, along with deformation and very low-to low-grade metamorphism of Mesoproterozoic cover rocks some time between 1070 and 755 Ma. However, we suggest that it involved regional amphibolite facies metamorphism and deformation, granite magmatism and pegmatite intrusion between c. 1030 and c. 950 Ma. Therefore, the Capricorn Orogen experienced a major phase of tectonic reworking c. 600 Myr later than previously recognized. Our results emphasize the importance of in situ geochronology integrated with petrological studies in order to link the metamorphic history of a terrane with causally related tectonic events.

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Experimental silicate mineral/melt partition coefficients for beryllium and the crustal Be cycle from migmatite to pegmatite

Cited by 81 publications

References 46 publications

Timing relationships between pegmatite emplacement, metamorphism and deformation during the intra‐plate Alice Springs Orogeny, central Australia

Timing relationships between pegmatite emplacement, metamorphism and deformation during the intra‐plate Alice Springs Orogeny, central Australia

Mineralogical and Geochemical Characterization of Beryl‐Bearing Granitoids, Eastern Desert, Egypt: Metallogenic and Exploration Constraints

Grenvillian‐aged orogenesis in the Palaeoproterozoic Gascoyne Complex, Western Australia: 1030–950 Ma reworking of the Proterozoic Capricorn Orogen

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