Occurrence and Chemical Composition of Minerals from the Pallancata Ag Mine, Peru

2019 ◽  
Vol 32 (2) ◽  
pp. 87-102
Author(s):  
Bong Chul Yoo ◽  
◽  
Jorge Acosta
Keyword(s):  
Chemical Composition ◽  
Composition Of Minerals

scholarly journals MINERAL CHEMISTRY AND GEOCHEMISTRY OF HYPERSTHENE-BEARING DIORITE FROM ERUSU AKOKO, SOUTHWESTERN NIGERIA

2020 ◽  
Vol 4 (1) ◽  
pp. 13-18
Author(s):  
E. J. Oziegbe ◽  
V. O. Olarewaju ◽  
O. O. Ocan
Keyword(s):  
Chemical Composition ◽  
Chemical Properties ◽  
Mineral Chemistry ◽  
Accessory Mineral ◽  
Southwestern Nigeria ◽  
Hydrous Minerals ◽  
Icp Ms ◽  
Composition Of Minerals ◽  
Textural Relationship ◽  
Opaque Minerals

Samples of mafic intrusive rock were analyzed for their mineralogical and chemical properties. The textural relationship was studied using the petrographic microscope, elemental composition of minerals was determined using the Electron Microprobe and the whole rock chemical analysis was done using the XRF and ICP-MS. The following minerals were observed in order of abundance; pyroxene, amphibole, plagioclase, biotite, opaque minerals, quartz and chlorite, with apatite and zircon occurring as accessory mineral. Two types of pyroxenes were observed; orthopyroxene (hypersthene) and clinopyroxene. Texturally, amphiboles have inclusions of plagioclase and pyroxene. The plagioclase has undergone sericitization. The chemical composition of the pyroxene is En51.95Fs44.53Wo3.52, biotite has Fe/(Fe+Mg):0.42, Mg/(Fe+Mg):0.59, and plagioclase is Ab63.5An34.55Or1.95. Whole rock chemistry shows a chemical composition; SiO2: 45.15 %, Al2O3: 14.04 %, Fe2O3: 16.01 %, MgO: 5.65 %, CaO: 7.58 % and TiO2: 3.59 %. There is an enrichment of LREE and a depletion of HREE. Based on the minerals, mineral chemistry and the geochemistry of the studied rock, the rock is mafic and hydrous minerals formed by hydration recrystallization of pyroxene. The rock has extensively retrogressed but has not been affected by any form of deformation.

scholarly journals Preparation of Thin Sections

1998 ◽  
Vol 6 (7) ◽  
pp. 8-9
Author(s):  
Ian Chaplin
Keyword(s):  
Chemical Composition ◽  
Thin Section ◽  
Microprobe Analysis ◽  
Rock Sample ◽  
Rock Type ◽  
X Rays ◽  
Thin Sections ◽  
Economical Method ◽  
Optical Examination ◽  
Composition Of Minerals

The optical examination of a rock sample in thin section is the quickest and most economical method for classifying rock type and determining which analytical route to follow.Thin sections for transmitted light are the most common, but there are also:Polished Thin Sections • Polished sections are used for classification and identification of minerals that cannot be determined in standard thin sections. They are also essential for microprobe analysis. Minute mineral grains are analyzed by bombarding them with a focused bean of electrons, which generate x-rays, characteristic of the elements within the grains. X-rays are identified and quantified to determine the chemical composition of minerals.

scholarly journals Contribution to the chemical composition of minerals of the mimetite-pyromorphite series from the Guatomo mine near Tham Thalu, Bannang Sata District, Yala Province (Thailand)

2020 ◽  
Vol 28 (2) ◽  
pp. 237-245
Author(s):  
Martin Števko ◽  
Jiří Sejkora ◽  
Zdeněk Dolníček
Keyword(s):  
Chemical Composition ◽  
Composition Of Minerals ◽  
Host Rocks ◽  
Compositional Series

The Guatomo mine is considered as one of the classic localities of mimetite worldwide. The chemical composition of six samples of minerals of mimetite-pyromorphite series from the Guatomo mine, representing different morphologies, colours as well as various geological environments/host rocks, was studied in detail by EMPA-WDS. This study revealed that both mimetite as well as pyromorphite are present at the Guatomo mine, representing rather variable compositional series ranging from the nearly end member mimetite (sample M1 - up to 0.03 apfu of P, sample M4 - up to 0.23 apfu of P and sample M5 with up to 0.18 apfu of P), through P-enriched mimetite (with 0.38 apfu of P) and As-rich pyromorphite (with 0.82 apfu of As, sample M2) up to As-enriched pyromorphite (sample M3 with As content reaching up to 1.03 apfu and sample M6 with up to 0.80 apfu of As). Besides of Pb, As, P and Cl only negligible amounts of Ca, V and S were detected in studied samples.

Mineralogy and petrology of ultramafic section of Kukesi Massif, Mirdita Ophiolite (Albania) – preliminary results

2020 ◽  
Author(s):  
Jakub Mikrut ◽  
Magdalena Matusiak-Małek ◽  
Jacek Puziewicz ◽  
Kujtim Onuzi
Keyword(s):  
Chemical Composition ◽  
Chemical Diversity ◽  
Troodos Ophiolite ◽  
Melt Extraction ◽  
Al Content ◽  
Mantle Peridotites ◽  
Wide Range ◽  
Scientific Project ◽  
Composition Of Minerals ◽  
High Degree

<p>Mirdita Ophiolite in northern Albania is a part of 30-40 km wide ophiolitic Pindos Zone in Dinaride-Hellenide part of the Alpine orogenic system (e.g. Dilek & Furnes 2009, Lithos). Mantle and crustal sections in the eastern part of this zone have Supra-Subduction Zone geochemical affinities. The goal of our study is to examine chemical diversity of rocks within Kukesi Massif and to decipher its evolution.</p><p>The Kukesi Massif is composed mostly of coarse- to medium-grained spinel harzburgites and dunite with chromite layers (e.g. Morishita et al. 2011, Lithos), locally  cross-cut by orthopyroxenite veins. Uppermost part of the sequence consist of cumulate pyroxenites and peridotites (composed of olivine, orthopyroxene, clinopyroxene and spinel). Most of the rocks are pervasively serpentinised, but degree of serpentinisation varies within the massive. Samples of peridotites and pyroxenites from over a dozen localities within the massif were collected.</p><p>Olivine occurring in the lower sections of the ophiolite has composition of Fo<sub>89.5-91.2</sub> (NiO 0.28-0.52 wt.%) in peridotites and Fo<sub>90.6-92 </sub>(NiO 0.38-0.52 wt.%) in orthopyroxenite veins. Olivine forming cumulates has Fo<sub>82.4-83.3</sub> and NiO content=0.12-0.23 wt. %. Orthopyroxene (enstatite) in mantle peridotites is Al-poor (0.05-0.08 Al a.p.f.u.) and has Mg# 90.5-91.5. Orthopyroxene from peridotite cut by orthopyroxenite veins is even poorer in Al (0.03-0.04 a.pfu) and has lower Mg# 91.1-91.7 and is chemically indistinguishable from pyroxenitic orthopyroxene. Orthopyroxene forming cumulates has Mg#=82.3-84.0 and the highest Al content among all the lithologies (0.12-0.14 a.p.f.u.). Peridotitic clinopyroxene (diopside) has Al=0.02-0.08 a.p.f.u. which corresponds well to this in orthopyroxene, but Mg# is higher – 92.5-95.4. Clinopyroxene in cumulate rocks has Al content=0.13-0.16 a.p.f.u. and Mg#=87-88. Spinel in mantle peridotites has Cr#=0.47-0.80 and is negatively correlated with Mg# (0.38 to 0.56). The cumulative spinel has lower Cr# (0.18-0.27), but the  Mg# is similar to that forming peridotite (0.38-0.45). </p><p>The orthopyroxene equilibration temperatures calculated with Witt-Eickschen & Seck (1991, CMP) algorithm, yield wide range of temperatures (800-950˚C in mantle peridotites and 950-1020˚C in cumulate peridotites suggesting its magmatic origin). Low Al content in orthopyroxene suggest that peridotites suffered from high degree of melt extraction.</p><p>Chemical composition of minerals forming rocks of Kukesi Massif is typical  for mantle sections of SSZ ophiolites (e.g. Troodos ophiolite, Batanova & Sobolev 2000, Geology). Our preliminary mineral chemical data for Kukesi ultramafics have a wider range than those previously obtained by Morishita et al. (2011, Lithos). The chemical composition of ultramafic rocks within this massif varies, which may result from variable geochemical history, but further studies are required to fully characterize the composition of Kukesi ultramafics and to reconstruct its geochemical and tectonic evolution.</p><p>This study was financed from scientific funds for years 2018-2022 as a scientific project within program “Diamond Grant” (DI 024748).</p>

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