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MinPlot: A mineral formula recalculation and plotting program for electron probe microanalysis

Walters Jesse B.

Mineralogia

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2022

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Vol. 53, iss. 1

51--66

EN

MinPlot is a MATLAB®-based mineral formula recalculation and compositional plotting program for electron microprobe analyses (EPMA). The program offers recalculation and structural formula assignment for 15 different mineral groups: Garnet, pyroxene, olivine, amphibole, feldspar, mica, staurolite, cordierite, chlorite, chloritoid, talc, epidote, titanite, spinel, and sulfides. MinPlot is a fast and easy to use command line program and requires no prior computer programming knowledge. Percent mass fractions of oxides are loaded from datafiles and the user answers simple prompts to select mineral type, normalization scheme, and plotting options. Recalculated mineral formulas are automatically saved as output files and plots may be further manually customized by the user prior to saving. MinPlot can perform thousands of calculations in seconds and the modular nature of the program makes it simple to add new calculation routines in future releases. Combined, these features make MinPlot a powerful and useful program for the processing of EPMA data.

2

Chevkinite-group minerals in Poland

Nejbert Krzysztof, Bagiński Bogusław, Kotowski Jakub, Jokubauskas Petras, Jurewicz Edyta, Macdonald Ray

Acta Geologica Polonica

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2020

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Vol. 70, no. 1

97--106

EN

The chevkinite group of minerals are REE,Ti-silicates increasingly recognized as widespread accessory phases in a wide range of igneous and metamorphic parageneses. Members of the group are here recorded from five localities in Poland: a two-pyroxene andesite from the Kłodzko-Złoty Stok intrusion, a trachyandesite intrusion north of the Pieniny Mountains, a rapakivi-type granite from the Krasnopol intrusion, an anorthosite from the Suwałki Anorthosite Massif, and nepheline syenite from the Ełk syenite massif. Specific members found are chevkinite-(Ce), perrierite-(Ce) and, potentially, the Al-dominant analogue of perrierite-(Ce). The case is made that chevkinite-group minerals will, through systematic investigation, be found in a wide range of Polish igneous and metamorphic rocks.

3

Mineral chemistry and thermobarometry of plutonic, metamorphic and anatectic rocks from the Tueyserkan area (Hamedan, Iran)

Sepahi A. A., Borzoei K., Salami S.

Geological Quarterly

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2013

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Vol. 57, No. 3

515–-526

EN

The study area is a part of the NW to SE striking Sanandaj–Sirjan metamorphic belt in western Iran. The Alvand Pluton, consisting of rocks that range in composition from gabbro to granite, is the major magmatic rock complex of this area. Gabbroic rocks include olivine gabbro, gabbro norite, norite and gabbro. Rocks around the Alvand Pluton were subjected to different P–T conditions due to polymetamorphism. Common metamorphic rocks are meta-pelites, but some meta-psammites, meta-basites and meta-carbonates also occur. Slates, phyllites, schists, migmatites and hornfelses are major rock units of meta-pelites in the metamorphic sequence. Based on mineral chemistry, the highest temperature of crystallisation (1300°C) was determined for the olivine gabbros, and the lowest temperature (950°C) was calculated for the hornblende-bearing gabbros. Clinopyroxene–plagioclase barometry suggests that pressures near 5 to 6 kbars prevailed during the crystallisation of the various mafic rocks. P–T estimates yield maximum temperatures of 700–750°C at 5–6 kbars for the high-grade metamorphic rocks from the metamorphic aureole around the pluton. These results indicate that the heat released from the Alvand Pluton (T = 950–1300°C), which intruded the metamorphic rocks at middle and upper crustal levels, was sufficient to cause partial melting leading to formation of the metatexites, diatexites and restite-rich S-type granites. During this process, part of the deep-seated gabbro-dioritic rocks were transported to higher crustal levels by viscous, enclave- and crystal-rich granitic magmas of the partial melting zone.

4

Cobalt-rich lithiophorite from the Precambrian Eastern Ghats manganese ore deposit of Nishikhal, south Orissa, India

Rao D. S., Nayak B. K., Acharya B. C.

Mineralogia

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2010

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Vol. 41, iss. 1/2

11--21

EN

Fine-grained aggregates of lithiophorite are associated with cryptomelane, romanèchite, birnessite and graphite in the Precambrian Eastern Ghats manganese ore deposit of Nishikhal, south Orissa, India. High-cobalt lithiophorite is reported for the first time from the manganese ores. The mode of occurrence and the chemical composition of the lithiophorite are discussed. Along with manganese and aluminium, the lithiophorite contains appreciable quantities of CoO (1.59-8.56%) together with trace amounts of Cu, Ni, Zn, Ti, Ca, Mg, Na, K and P. The Nishikhal lithiophorite is a transition metal-rich lithiophorite.

5

Late Palaeozoic lamprophyres and associated mafic subvolcanic rocks of the Sudetes (SW Poland): petrology, geochemistry and petrogenesis

Awdankiewicz M.

Geologia Sudetica

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2007

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Vol. 39

11-97

EN

Lamprophyric magmatism in the Sudetes, in the eastern part of the European Variscides, occurred during a period of post-collisional extension in the Carboniferous. The lamprophyres (minettes, vogesites, spessartites, kersantites) and associated mafic rocks (monzonites, micromonzodiorites) were emplaced as dyke swarms and as scattered veins that cut the crystalline basement and, locally, the overlying molasse deposits. The dyke swarms are adjacent to major regional dislocations, represent distinctive magmatic centres that are related to separate magmatic systems and each are characterized by specific parental melts that have undergone individualised shallow-level differentiation processes. The two largest dyke swarms are associated with the Karkonosze and Kłodzko-Złoty Stok granitoid massifs: these show the widest geochemical and petrographic variation, due to more advanced differentiation in long-lived magmatic systems. In contrast, a small dyke swarm emplaced in the SW part of the Orlica-Śnieżnik Dome, unrelated to granites, is strongly dominated by minettes only. Geochemical characteristics of the mafic rocks studied herein vary from (ultra)potassic in the minettes to calc-alkaline in the micromonzodiorites and from primitive (Mg# = 80-60 in many lamprophyres) to evolved (Mg# down to 30 in some micromonzodiorites). Some richterite minettes show Nb-enriched trace element patterns, but negative Nb anomalies are more typical. Richterite minettes posesess ?Nd300 and 87Sr/86Sr300 values that range from +1.9 to -8.3, and from 0.7037 to 0.715, respectively. The other rocks in this study show negatively correlated Nd and Sr isotopic ratios, between these extremes. The geochemical data suggest three types of mantle source for the lamprophyres and associated mafic rocks: (1) An asthenospheric, depleted and later re-enriched source; (2) A lithospheric source contaminated by subducted crustal rocks; (3) A lithospheric source metasomatized by subduction-related fluids. The richterite minette magmas originated from low degrees of partial melting, under high H2O/CO2 conditions, of garnet-phlogopite-peridotites. The Nb-enriched and Nb-depleted minettes are derived from sources (1) and (2), respectively. Kersantite magmas originated from source (3). The factors of source mixing, variable depths and degrees of melting, and aggregation of melts all influenced the compositions of other primitive minette and vogesite magmas. The other rocks studied (spessartites, monzonites, micromonzodiorites) are variably differentiated. Zoning and other disequilibrium textures in phlogopite, biotite, amphibole and clinopyroxene phenocrysts, together with the presence of xenocrysts, xenoliths and enclaves (cognate, restitic, migmatitic) constrain several processes that were involved in the shallow-level evolution of magmas: mixing, fractional crystallization, assimilation of crustal rocks. However, post-magmatic replacement of the igneous phases by albite, chlorite, epidotes, actinolite, blue amphiboles, titanite, carbonates, prehnite, pumpellyite and grossularite-andradite partly obscures the magmatic assemblages and textures. There are four more general results of this study. First, there is evidence for a strong heterogeneity of the upper mantle and of the presence of subduction-modified mantle beneath the Sudetes during the Late Palaeozoic. Second, the lamprophyre magmas originated and evolved in spatially and petrologically distinct, vertically extensive magmatic systems that spanned the asthenospheric and lithospheric mantle and the lower/middle crust. Third, a broad spectrum of source-related and shallow-level magmatic processes gave rise to the emplacement of primitive, mantle-derived magmas and of variably evolved magmas. Fourth, close links existed between late Variscan tectonics, the location of lamprophyric magmatism, and the shallow-level emplacement processes of mafic dykes.

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Ilmenite-bearing ecologites of the West Sudetes -their geochemistry and mineral chemistry

Bakun-Czubarow N.

Archiwum Mineralogiczne

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1998

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T. 51, z. 1-2

29-110

EN

The paper presents new data on geochemistry and mineral chemistry of the ilmenite-bearing Sudetic eclogites which provide geochemical constraints on the geo-tectonic setting in which the igneous protoliths of these rocks were formed. Conditions and geodynamic regime of Variscan HP metamorphism the rocks underwent are also discussed. The ilmenite-bearing Sudetic eclogites outcrop on the slope of the Czemica Mountain within orthogneisses of Gierałtow unit in Orlica--Śnieżnik Dome (OSD) as well as within high-grade mica schists of Kamieniec Ząbkowicki in Fore-Sudetic Block (FSB). The igneous protoliths for the ilmenite-bearing Sudetic eclogites were tholeiites of ferrogabbroic chemical composition. The FSB eclogite magmatic protoliths may have been formed either at a slowly spreading oceanic ridge transected by a fracture zone or in a spreading centre of a marginal back-arc basin. The FSB eclogites display geochemical affinity to some volcanic and shallow level intrusive rocks of circum-Sowie Mountains ophiolites, particularly to the upper horizon rocks of the Slęża ophiolite, originated most likely in the environment of either narrow ocean or back-arc basin. Thus FSB eclogites represent most likely the HP upper part of a dismembered ophiolitic sequence. On the other hand, the OSD eclogites from the slope of the Czernica Mountain may have been originated at the expense of a camptonite-type lamprophyre within continental environment. The ilmenite-bearing eclogites of the FSB display the following climax metamorphism mineral assemblage: Omp-Grt-Gln-Hbl-Qtz-Zo-Ilm-Rt-Pg-Phe-Ap-Zrn, whereas the appropriate assemblage for the OSD quartzless eclogite is mineral poorer: Omp-Grt-Hbl-Zo-Ilm-Rt-Ttn-Phe-Ap. The conditions of extreme metamorphism for the FSB eclogites are 570-610°C under P min = 13-15 kbar, whereas for the OSD eclogites they are higher: 730 +/-30°C under P min = 15-16 kbar. The FSB ilmenite-bearing ophiolitic eclogites are subduction related and display clockwise P--T trajectory of EBS-EC-EA-GS type. On the other hand, the OSD Czernica eclogites register continental type collisional event in eastern termination of the West Sudetes with EC-AM-EA-GS trajectory of the retrograde metamorphism.

PL

W ekologitach właściwych (zwyczajnych), które występują w postaci stosunkowo niewielkich ciał wśród gnejsów migmatytowych i paragnejsów, ilmenit krystalizuje zwykle kosztem rutylu podczas metamorfizmu retrogresywnego, rzadko natomiast należy do paragenezy metamorfizmu ekstremalnego. Jeśli ilmenit wchodzi w skład wysokociśnieniowej paragenezy ekologitów, może on spełniać rolę geobarometru, bowiem udział geikielitu w roztworze stałym FeTiO3-MgTiO3 rośnie ze wzrostem ciśnienia równowagi mineralnej. W Sudetach Zachodnich ekologity właściwe występują głównie we wschodniej części jądra kopuły orlicko-śnieżnickiej-OSD, a ostatnio zostały także rozpoznane we wschodniej części blioku przedsudeckiego - FSB. Ilmenit, należący do wysokociśnieniowej paragenezy eklogitów własciwych, jest pospolitym minerałem akcesorycznym ekologitów FSB, zaś w OSD wystepuje tylko w ekologitach południowej części jednostki tektonicznej Gierałtowa. Celem mineralogiczno-geochemicznych badań porównawczych ilmenitonośnych ekologitów właściwych OSD i FSB było pełniejsze poznanie ich geochemii, chemii minerałów,warunków równowag mineralnych oraz znaczenia tych skał dla paleogeodynamiki najbardziej na wschód wysuniętej części lugicum, a także dla lokalizacji głównych granic tektonicznych w północno-wschodniej części masywu czeskiego.