0000000000718330
AUTHOR
George A. Jenner
Trace element partitioning in lamproitic magmas—the Gaussberg olivine leucitite
Abstract Partition coefficients for compatible and incompatible trace elements for use in modelling the origin and evolution of lamproitic and other potassic rocks are reported. These are based on values obtained by in situ determination using laser ablation microprobe-inductively coupled plasma-mass spectrometry (LAM-ICP-MS) on mineral/glass pairs in examples of the Gaussberg olivine leucitite, a classic leucite lamproite. Leucite/melt partition coefficients for 32 elements show values above 1 only for Cs and Rb, whereas values for Ni, Ga and Co are 0.4–0.1. DLc/Lq for most other elements are in the range 0.07–0.0005, and delineate a gently sloping pattern to lower values for elements gene…
Torngat ultramafic lamprophyres and their relation to the North Atlantic Alkaline Province
Geological mapping and diamond exploration in northern Quebec and Labrador has revealed an undeformed ultramafic dyke swarm in the northern Torngat Mountains. The dyke rocks are dominated by an olivine-phlogopite mineralogy and contain varying amounts of primary carbonate. Their mineralogy, mineral compositional trends and the presence of typomorphic minerals (e.g. kimzeyitic garnet), indicate that these dykes comprise an ultramafic lamprophyre suite grading into carbonatite. Recognized rock varieties are aillikite, mela-aillikite and subordinate carbonatite. Carbonatite and aillikite have in common high carbonate content and a lack of clinopyroxene. In contrast, mela-aillikites are richer …
Between carbonatite and lamproite - Diamondiferous Torngat ultramafic lamprophyres formed by carbonate-fluxed melting of cratonic MARID-type metasomes
Abstract New U–Pb perovskite ages reveal that diamondiferous ultramafic lamprophyre magmas erupted through the Archean crust of northern Labrador and Quebec (eastern Canada) between ca. 610 and 565 Ma, a period of strong rifting activity throughout contiguous Laurentia and Baltica. The observed Torngat carbonate-rich aillikite/carbonatite and carbonate-poor mela-aillikite dyke varieties show a large spread in Sr–Nd–Hf–Pb isotope ratios with pronounced correlations between isotope systems. An isotopically depleted component is identified solely within aillikites (87Sr/86Sri = 0.70323–0.70377; eNdi = +1.2–+1.8; eHfi = +1.4–+3.5; 206Pb/204Pbi = 18.2–18.5), whereas some aillikites and all mela-…
Integrating Ultramafic Lamprophyres into the IUGS Classification of Igneous Rocks: Rationale and Implications
RECEIVED JULY 16, 2004; ACCEPTED MARCH 16, 2005ADVANCE ACCESS PUBLICATION APRIL 29, 2005We introduce a modification to the current IUGS classificationsystem for igneous rocks to include ultramafic lamprophyres, whicharecurrentlyentirelyomitted.Thisisdonebyincludinganewstepinthe sequential system, after the assignment of pyroclastic rocks andcarbonatites, that considers ultramafic inequigranular textured rockswith olivine and phlogopite macrocrysts and/or phenocrysts. At thisstepultramaficlamprophyresareconsideredtogetherwithkimberlites,orangeites (former Group 2 kimberlites) and olivine lamproites.This proposal allows the correct identification and classificationof ultramafic lamprophyres w…