Ion Microprobe Determination of Rare Earth Elements in Perovskite from Kimberlites and Alnöites

Mitchell, Roger H.; Reed, S. J. B.

doi:10.1180/minmag.1988.052.366.04

Cited by 23 publications

(18 citation statements)

References 15 publications

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“…Perovskites in the micro-clasts were too small to analyse. All perovskites in P-12 are only slightly enriched in LREEs in common with other lamproite perovskites (Jaques et al 1986;Mitchell and Reed 1988;Mitchell and Bergman 1991;Mitchell 2002;Gurmeet Kaur and Mitchell 2013;. The cores of the zoned perovskites are more (Table 5).…”

Section: Perovskitementioning

confidence: 94%

Mineralogy of the P-12 K-Ti-richterite diopside olivine lamproite from Wajrakarur, Andhra Pradesh, India: implications for subduction-related magmatism in eastern India

Kaur

Mitchell

2015

Miner Petrol

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The P-12 Bpara-kimberlite^from Wajrakarur consists of forsteritic olivine, Al-Na-poor diopside, Fe-Tirich, Al-poor phlogopite, K-Ti-richterite, spinel, perovskite, cymrite, apatite, barite, Ba-Sr-bearing calcite, gittinsite, witherite, strontianite, and hydrogrossular (hydrogarnet). The rock also contains small clasts consisting dominantly of calcite, with lesser Ba-Srbearing calcite, cymrite, barite, strontianite, witherite, apatite, and hydrogrossular. Two generations of forsteritic olivine (Fo 80-93 ) crystals are present: common phenocrystalto-microphenocrystal; and rare anhedral macrocrystic olivines. Phlogopite occurs as microphenocrysts and as groundmass poikilitic plates with inclusions of spinel, perovskite, apatite, and chlorite pseudomorphs (after pyroxene). Phlogopites also occur as reaction rims around olivine crystals. The phlogopites have extremely low Al 2 O 3 (2.2-3.8 wt.%) , moderate-to-high FeO (6.9-16 wt.%), TiO 2 (1.9-4.6 wt.%), and Na 2 O (0.4-2.7 wt.%) contents and are enriched in fluorine (up to 6.0 wt.%) and considered to be tetraferriphlogopite. The pyroxenes occur in five parageneses as: (1) phenocrysts and microphenocrysts; (2) small slender crystals(<30 μm) forming part of the groundmass; (3) the cores of richterite crystals; (4) reaction products replacing earlier-formed olivine; (5) acicular crystals mantling carbonate clasts. These pyroxenes do not differ significantly in composition and are all diopsides with minor variation in their TiO 2 , Al 2 O 3 , Na 2 O contents. Titanian-potassium richterite commonly occurs as: (1) groundmass poikilitic plates;(2) small prismatic crystals (<30 μm); (3) reaction rims on olivine and pyroxene crystals. Groundmass poikilitic richterites commonly enclose pyroxene and apatite. Perovskites have a bimodal size distribution. Small (<20 μm) euhedral perovskites are scattered throughout the groundmass, whereas larger (100-300 μm) subhedral-to-euhedral perovskites are patchily-zoned and commonly broken. Micro-clasts consisting of accumulations of perovskite with phlogopite and apatite are also present. Spinels occur as large atoll crystals and small (<20 μm), euhedral-to-subhedral crystals, scattered throughout the groundmass. Some small spinel crystals are also present in the rims of olivine and pyroxene crystals. Atoll spinels are up to 100 μm in size, commonly with single and double cores. Atoll spinels are typically associated with perovskites. The euhedral-tosubhedral small spinels are ulvospinels. The atoll spinels have cores of titanian aluminous magnesiochromite with rims of magnesian titaniferous magnetite. The spinels have compositions which evolve along the lamproite-spinel compositional trend. Zoned calcite crystals occur as residual phases. Late stage residual calcite and carbonate clasts host prismatic cymrite crystals which are interpreted as pseudomorphs after potassium feldspar and/or barite. Subhedral-to-euhedral gittinsite and its Sr-analog are reported for the first time from the groundmass carbonatechlorite mesostasis of a lamproit...

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Section: Perovskitementioning

confidence: 94%

Mineralogy of the P-12 K-Ti-richterite diopside olivine lamproite from Wajrakarur, Andhra Pradesh, India: implications for subduction-related magmatism in eastern India

Kaur

Mitchell

2015

Miner Petrol

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“…The application of this approach to other REE-bearing accessory phases has been described by Reed (1986). Results for perovskite have been reported recently by Mitchell and Reed (1988).…”

Section: Applicationsmentioning

confidence: 92%

“…Reed et al (1988) have reported measurements on pitchblende from the Olympic Dam ore deposit, S. Australia, using the ion microprobe for the Pb isotopes and electron microprobe analysis of the same spots for determining U/Pb ratios.…”

Section: Applicationsmentioning

confidence: 99%

Ion microprobe analysis—a review of geological applications

Reed

1989

Mineral. mag.

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In ion microprobe analysis the specimen is bombarded with a focussed ion beam a few #m in diameter and the secondary ions produced are accelerated into the entrance slit of a mass spectrometer. An outline of the salient features of the instrument is given here, together with an account of the methods used for quantitative elemental and isotopic analysis.The major part of this paper consists of a comprehensive account of the geological applications of ion microprobe analysis. These include elemental analysis, especially for trace elements (down to subppm levels in many cases) and light elements (H F) which are beyond the scope of the electron microprobe. The other main area of geological interest is isotopic analysis, where the ion microprobe has the advantage over conventional mass spectrometry of being capable of in situ analysis of selected points on polished sections, obviating the need for laborious specimen preparation, and enabling spatially-resolved data to be obtained, with a resolution of a few #m. The ion microprobe has been especially successful in U Pb zircon dating and the study of isotope anomalies in meteorites. Other significant applications include diffusion and stable isotope studies.

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“…Evidentemente, a microssonda (WDS) não é o equipamento melhor adaptado para a dosagem de ETR, sobretudo quando estes se apresentam em fracas concentrações, o que é geralmente o caso. Se, por um lado, sua utilização apresenta a vantagem de evitar separações de fases, normalmente impossíveis de serem realizadas nos alteritos, devido ao tamanho dos cristais neoformados e do íntimo estado de agregação dos minerais, por outro, a existência de interferências entre as raias X dos ETR faz com que seja difícil detectar teores inferiores a 200 ppm para qualquer um desses elementos (Roeder 1985, Mitchell & Reed 1988. Sobre a raia Lα 1 , que é a mais intensa, somente La, Ce, Nd, Sm, Tb, Dy e Yb podem ser dosados sem correções e sobre a raia Lβ 1 menos intensa, somente Ce, Pr, Nd, Sm e Dy.…”

Section: Amostragem E Métodos De Estudo Osunclassified

Comportamento Geoquímico Dos Elementos Terras Raras Nos Alteritos Da Jazida De Fosfato E Titânio De Tapira (Minas Gerais, Brasil): A Importância Dos Fosfatos

SOUBIÈS¹,

MELFI²,

AUTEFAGE³

1991

RBG

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The geochemical behaviour of the rare earth elements (REE) during the supergenic evolution of the rocks is not yet well known. This paper deals with the REE behaviour in ferralitic alteration profiles of the residual phosphate and titanium deposit of Tapira, originated from pyroxenites and peridotites containing apatite and perovskite. This study was carried out on a rock constituted essentially of apatite, perovskite and titaniferous magnetite, with diopside and phlogopite as accessory minerals. The analysis of a microfractured and silicified fresh rock has shown perovskite as the main bearing REE primary mineral (1.5 to 2.0% RE 2 O 3). The alteration of this rock occuring on a first stage with preservation of the volume (isovolume) leads to: 1. total removal of silica (opal and quartz); 2. partial dissolution of primary apatite along the fractures and neoformation of secondary apatite, enriched in fluor and depleted in REE; and 3. total transformation (pseudomorphose) of perovskite into microbothroidal anatase in the voids of which a crystal association (geodes) of rare earth and Ca phosphate of rhabdophane group is neoformed. On a second alteration stage it is observed that: 1. all the apatite is dissolved leaving behind important assembly of voids; 2. the phosphate of the rhabdophane group is partially dissolved and replaced by a phosphate of the crandallite group rich in REE; 3. a certain Ti mobilization occurs in the interior of the anatase (corrosion gulf; titaneous cutans) followed by its partial epigenization by ferruginous products and an initial alteration of the titaniferous magnetite. The study seems to indicate that in Tapira: 1. the phosphorous has a fundamental role on trapping the REE released by hydrolysis of the bearing primary minerals; 2. the REE remain in the alterites and are fixed in mineralogical phases of a sequence of REE phosphates richer in aluminium; 3. the REE and the Ti remain closely associated in the studied weathering phases.

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Ion Microprobe Determination of Rare Earth Elements in Perovskite from Kimberlites and Alnöites

Cited by 23 publications

References 15 publications

Mineralogy of the P-12 K-Ti-richterite diopside olivine lamproite from Wajrakarur, Andhra Pradesh, India: implications for subduction-related magmatism in eastern India

Mineralogy of the P-12 K-Ti-richterite diopside olivine lamproite from Wajrakarur, Andhra Pradesh, India: implications for subduction-related magmatism in eastern India

Ion microprobe analysis—a review of geological applications

Comportamento Geoquímico Dos Elementos Terras Raras Nos Alteritos Da Jazida De Fosfato E Titânio De Tapira (Minas Gerais, Brasil): A Importância Dos Fosfatos

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