Teresa E. Jeffries

Natural History Museum

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Javier Fernández‐Suárez

Universidad Complutense de Madrid

Alberto Pérez‐Huerta

Geological Survey of Alabama

Craig Storey

University of Portsmouth

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Živilė Žigaitė

Uppsala University

Frances Wall

University of Exeter

Ricardo Arenas

Universidad Complutense de Madrid

J. Brendan Murphy

St. Francis Xavier University

Martin Smith

University of Brighton

J. Duncan Keppie

Universidad Nacional Autónoma de México

John Spratt

Natural History Museum

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Natural History Museum

Universidad Complutense de Madrid

Consejo Superior de Investigaciones Científicas

Universidad de Salamanca

Russian Academy of Sciences

Instituto de Geociencias

Centre National de la Recherche Scientifique

German Oceanographic Museum

Eötvös Loránd University

Planetary Science Institute

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XENOTIME-(Y) FROM CARBONATITE DYKES AT LOFDAL, NAMIBIA: UNUSUALLY LOW LREE:HREE RATIO IN CARBONATITE, AND THE FIRST DATING OF XENOTIME OVERGROWTHS ON ZIRCON

The Canadian Mineralogist (2008)

Frances Wall V. N. Niku-Paavola Craig Storey Axel Müller Teresa E. Jeffries

Xenotime-(Y) is a common accessory mineral in many igneous and high-grade metamorphic rocks, but it is very rare in carbonatite. Uniquely, at Lofdal, Namibia, xenotime-(Y) occurs in many carbonatite dykes. It mantles and replaces zircon in calcite carbonatite and also occurs as aggregates in ankerite carbonatite, aggregates associated with hematite, and crystals associated with monazite-(Ce) and synchysite-(Ce) in highly oxidized iron-rich calcite carbonatites. The paragenetic sequence places the xenotime-(Y) at the end of magmatic activity and certainly into the hydrothermal stage. A U-Pb date of 765 +/- 16 Ma (2 sigma) for xenotime-(Y) overgrowths on zircon obtained by LA-ICP-MS, the first dating of fine overgrowths of xenotime on zircon by this technique, confirms that the formation of xenotime-( Y) is directly related to the crystallization of the carbonatite and provides a date consistent with published dates for Lofdal and Oas syenites. The xenotime-(Y) is heavy-REE-enriched (chondrite-normalized graphs peak at Lu) but can be distinguished from xenotime-(Y) in granitic rocks by the lack of Eu anomaly, higher Gd (reaching > 6 wt%) and lower Yb (below 4 wt%). A monazite-(Ce) - xenotime-(Y) geothermometer developed for metamorphic rocks gives possible but relatively high temperatures of > 450 degrees C for the formation of xenotime-(Y). Overall, the whole-rock compositions are light-REE-enriched, in common with most carbonatites, but the degree of light REE enrichment is less than almost all published datasets (La/Yb-n at Lofdal ranges from 1 to 70), and at 0.5-0.8 wt%, the total REE content at Lofdal is also higher than in many carbonatites. These features are most important in controlling the production of xenotime-( Y) at Lofdal. Exploration for Y in carbonatites should therefore concentrate on rocks that have REE concentrations above 2000 ppm and La/Yb values lower than 70, similar to Lofdal, as well as weathered carbonatite regoliths and carbonatites subjected to extreme hydrothermal conditions, where Y can be concentrated.

Carbonatite

10.3749/canmin.46.4.861

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Citations (81)

Rare earth elements in phoscorites and carbonatites of the Devonian Kola Alkaline Province, Russia: Examples from Kovdor, Khibina, Vuoriyarvi and Turiy Mys complexes

Ore Geology Reviews (2014)

Anatoly N. Zaitsev C. T. Williams Teresa E. Jeffries Stanislav Strekopytov Jacques Moutte

Carbonatite

Metasomatism

Magnesite

10.1016/j.oregeorev.2014.02.002

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Citations (56)

COMPOSITIONAL ZONING OF RAPAKIVI FELDSPARS AND COEXISTING QUARTZ PHENOCRYSTS

The Canadian Mineralogist (2008)

Axel Müller Reimar Seltmann Bernd Kober Olav Eklund Teresa E. Jeffries

The compositional zoning of plagioclase-mantled K-feldspar, defining the rapakivi texture, and of the associated quartz phenocrysts from the Paleozoic Land’s End (U.K.) and Altenberg–Frauenstein (Germany) granites, and the Proterozoic Hammarudda (Finland) granite porphyry, has been investigated by laser-ablation – inductively coupled plasma – mass spectrometry, electron-probe micro-analyses, cathodoluminescence and thermal ionization mass spectrometry in order to investigate the formation of the rapakivi texture in two different eons. Recent analytical developments and the Ti-in-quartz geothermometer lead to interpretations of the trace-element zoning in quartz phenocrysts coexisting with rapakivi feldspars. There is an approximate coincidence with Ba-rich growth zones in plagioclase-mantled K-feldspar and Ti-rich zones in coexisting quartz phenocrysts. Both types of zoning indicate increasing temperatures of crystallization. The formation of the plagioclase mantles seems to be related to quartz-resorption events. The inferred temperature of crystallization increased after marginal resorption of quartz phenocrysts by about 82°C in the Altenberg–Frauenstein magma and 44°C in the Hammarudda magma, on the basis of the Ti-in-quartz geothermometer. The temperature increase is correlated positively with the crystallization of plagioclase mantles on the K-feldspar. The quartz phenocryst in the Land’s End granite shows normal core-to-rim zoning of Ti (decreasing concentrations), indicating a gradual decrease in magma temperature. We contend that the increase in the quartz-crystallization temperature of >25°C after a resorption event is indicative for the interaction with mafic magma. Therefore, the interaction of a crystal-saturated granitic magma and a mafic magma is the driving force causing nucleation and crystallization of plagioclase on K-feldspar phenocrysts, even though the Pb isotope, Ba, Sr, and Rb zoning of the mantled K-feldspar phenocryst have not clearly recorded an interaction between granitic and mafic magmas. The frequency of rapakivi feldspars in the rock correlates with the portion of mafic magma involved in the mingling and mixing process. Isothermal decompression during adiabatic magma ascent may have contributed to the plagioclase mantle formation in the case of the Altenberg–Frauenstein and Hammarudda granites. The rare rapakivi feldspars in the Land’s End granite developed during an early stage of magmatic evolution; as a result, tracing the conditions of formation of the rapakivi texture is speculative in that case.

Phenocryst

10.3749/canmin.46.6.1417

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Citations (32)

Multiple provenance of detrital zircons from the Permian–Triassic boundary in the Bükk Mts., Hungary

International Journal of Earth Sciences (2009)

Norbert Zajzon Zsófia Szabó Tamás Weiszburg Teresa E. Jeffries

Radiometric dating

10.1007/s00531-009-0500-y

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Citations (8)

Contiguous rather than discrete Paleozoic histories for the Avalon and Meguma terranes based on detrital zircon data

Geology (2004)

J. Brendan Murphy Javier Fernández‐Suárez J. Duncan Keppie Teresa E. Jeffries

Upper Ordovician–Lower Devonian strata of the Meguma terrane in the Canadian Appalachians contain zircon populations, including an important Mesoproterozoic zircon population (1.0–1.4 Ga), similar to those in coeval strata of Avalonia, and strongly suggest contiguous rather than discrete histories for these terranes throughout the Paleozoic. That these terranes were juxtaposed throughout the early Paleozoic is indicated by the absence of a Cambrian–Ordovician accretionary event, the lack of intervening suture-zone ophio litic units, and the similarity of Avalonian and Meguma basement Nd isotope signatures in early Paleozoic igneous suites. As Avalonia had accreted to Laurentia-Baltica by the Early Silurian, these data suggest that the Meguma terrane, like Avalonia, resided along the same (northern) margin of the Rheic Ocean at that time. These conclusions have implications for reconstructions of the northern Gondwanan margin in the early Paleozoic and imply that the Silurian–Devonian Acadian orogeny in Maritime Canada occurred in an Andean-type setting and was not related to collision of the Meguma terrane with the Laurentian margin.

10.1130/g20351.1

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Citations (132)

Palaeoenvironmental signatures revealed from the Silurian dental apatite : : rare earth element and stable isotope record

Živilė Žigaitė Alberto Pérez‐Huerta Teresa E. Jeffries Michael M. Joachimski Henning Blom

Palaeoenvironmental signatures revealed from the Silurian dental apatite : : rare earth element and stable isotope record

Rare-earth element

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Experimental study of interphase partitioning of rare elements in diamond forming eclogite-carbonatite and peridotite-carbonatite systems

Vestnik Otdelenia nauk o Zemle RAN (2011)

A. V. Kuzyura Yu. А. Litvin V. Yu. Okoemova P. G. Vasiliev Frances Wall

Carbonatite

Peridotite

10.2205/2011nz000190

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LREE distribution patterns in zoned alkali feldspar megacrysts from the Karkonosze pluton, Bohemian Massif - implications for parental magma composition

Mineralogical Magazine (2007)

Ewa Słaby Reimar Seltmann Bernd Kober Axel Müller Luiza Galbarczyk-Gąsiorowska

Abstract The elemental compositions of zoned alkali feldspar megacrysts from the Karkonosze pluton have been analysed and Pb isotope ratios determined using LA-ICP-MS, EMPA and TIMS. The results are used to interpret the magmatic environments within which they crystallized. Growth zones in the megacrysts show fluctuating trace element patterns that reflect a systematic relationship between incompatible LREE and compatible Ba. Chemical gradients between zones in the cores and rims of the megacrysts are not accompanied by significant variation in initial Pb isotope composition. The nucleation and crystallization of the megacrysts is interpreted as having occurred in an environment of magmatic hybridization caused by mixing of mantle and crustal components in which effective homogenization of the Pb isotope composition preceded the onset of megacryst growth. The concentrations of LREE in alkali feldspar zones were used to reconstruct hypothetical melt compositions. Some of the zones appear to have crystallized in an homogenous magmatic environment having clear geochemical affinities with end-member magmas in the Karkonosze pluton, whereas others crystallized in heterogeneous domains of magma hybridization. With the exception of Nd, zones crystallized in more homogeneous magma show LREE fractionation under near-equilibrium conditions. Trace element abundances of megacrysts grown in dynamic, homogeneous magmatic environments of the Karkonosze pluton occasionally deviate from the predicted patterns and show LREE impoverishment.

Alkali feldspar

Fractional crystallization (geology)

Igneous differentiation

Massif

Trace element

Incompatible element

10.1180/minmag.2007.071.2.155

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Citations (26)

Trace elements mineral-melt partitioning in diamond-forming peridotite-carbonatite system (experimental study at 8.5 GPa)

EGU General Assembly Conference Abstracts (2012)

A. V. Kuzyura Yu. А. Litvin P. Vasilisev Teresa E. Jeffries Frances Wall