Showing: 1 - 4 of 4 RESULTS
Nezaradené

New mineral parahibnitte approved by IMA

Ferrous hydroxychlorides hibbingite (γ-Fe2(OH)3Cl) and parahibbingite (β-Fe2(OH)3Cl) as a 1 concealed sink of Cl and H2O in ultrabasic and granitic systems

Peter Koděra, Juraj Majzlan, Kilian Pollok, Stefan Kiefer, František Šimko, Eva Scholtzová, Jarmila Luptáková a Grant Cawthorn

American Mineralogist 2022, Vol. 7, 826-841 – Link

Abstract

Ferrous hydroxychlorides are geochemically important but less recognized mineral species due to their extreme sensitivity to oxidation and hydration in contact with air {typically they convert to akaganéite [Fe3+(O,OH,Cl)]}. Only the γ-form was previously known as the orthorhombic mineral hibbingite, associated with altered mafic intrusive rocks. In this study, we describe the β-polymorph of Fe2(OH)3Cl as a new mineral parahibbingite that was found in pyroxenite from the Karee platinum mine in the Bushveld Complex, South Africa. The two minerals were distinguished by a combination of Raman spectroscopy and FIB-SEM-TEM analytical techniques (TEM-EDX and TEM-SAED). They can be easily recognized by their distinct Raman spectra. Parahibbingite has two very strong vibration bands at ~3550 and 3560 cm–1, accompanied by much weaker bands at ~124 and 160 cm−1, while the Raman spectrum of hibbingite has a sharp, strong band at 3450 cm−1 and two moderate bands at 199 and 385 cm−1.

Parahibbingite was found as fine-grained reaction rims at the contact of orthopyroxene phenocrysts and talc inside a drill core. It has a trigonal space group [R3m, a = 6.94(5) Å; c = 14.5(2) Å], with an empirical formula (⁠Fe2+1.98Mn2+0.01Fe1.982+Mn0.012+Ca0.01)(OH)3.08Cl0.92. The origin of this mineral in the Bushveld Complex is most likely related to a late hydrothermal alteration of pyroxenite. Hibbingite forms as an abundant daughter mineral hosted by fluid inclusions and salt melt inclusions in hydrothermal quartz associated with granitic systems during cooling under reducing conditions. Such inclusions are common in Au-porphyry mineralization worldwide, such as the Biely Vrch (Slovakia) deposit studied in detail in this work. The lattice parameters obtained by TEM-SAED are a = 6.30 Å, b = 7.12 Å, and c = 9.89 Å.

Images of Hibbingit (Hib) and Parahibbingite (Phb) in the sample of pyroxenite from the Bushveld Complex (JAR).

Hibbingite was recognized as the only phase that carries “water” (as a hydroxyl group) in otherwise water-free, salt melt inclusions. Furthermore, both hibbingite and parahibbingite should be considered as reservoirs for Cl and H2O in large volumes of altered basic and ultrabasic rocks. They can transport volatiles to shallow levels of subduction zones. Alternatively, their dissolution can fuel remobilization, transport, and deposition of sulfidic ores in saline fluids. Their detection, however, is difficult because of their sensitivity to oxidizing atmospheres. For example, in natural outcrops exposed to air, they may vanish, thus distorting estimates of their abundance and role in many processes that involve mineral-derived volatiles.

Nezaradené

Lecture – Introduction to Data Analysis in Geosciences

We are pleased to announce a series of seminars on data analysis in geosciences. The duration will be approximately 30-45 min. and the tutor is Liubomyr Gavryliv, PhD. from the Department of Mineralogy, Petrology and Economic Geology, FNS CU. Liubomyr currently works as a MarieSkłodowska-Curie research fellow in the UK and develops a multidimensional relational data model for mineralogical data analysis.

The seminar will go into the fundamentals of data analysis and its practical implications in mineralogy and geology
with a few examples from the tutor’s experience. We will discuss the following topics:

(1) What is data analysis and is it important in mineralogy?
(2) Most popular programming languages and tools for data analysis: Python and R
(3) Data collection: principal methods and drawbacks
(4) Data cleaning and transformation
(5) Data warehouse: databases vs temporary data storages
(6) Important resources for making data analysis

A short discussion will take place about the general improvement of research quality by the employment of
data analysis techniques with key examples.

Venue:
Faculty of Natural Sciences, Comenius University, Ilkovičova 6, Bratislava
Date and time: March 24, 2022 at 15:00
Room: AMOS

Nezaradené

Support to Ukraine

The Department of Mineralogy, Petrology and Economic Geology express support and solidarity to the people of Ukraine. We hope that peace will be restored as soon as possible.

A shot from the peaceful candlelight march, that took place on February 24, 2022 from 6 PM in Bratislava and was attended by thousands of people. 

Nezaradené

22.04.2021 – Online defenses of written thesis for the dissertation exam

The Department of Mineralogy, Petrology and Economic Geology invites you to public online defenses of written thesis for the dissertation exam, which will take place on April 22, 2021. Below you will find public link for connection via the MS Teams application. 22.4.2021 at 9:00 (Alex Molnárová) and 11:00 (Olena Rybnikova).

Mgr. Alex Molnárová – 22.4.2021 o 9:00 (in Slovak)
Geochemistry of granitoid rocks in the Fabova Hola and Eastern Lower-Tatra Areas
MS Teams Link

MSc. Olena Rybnikova – 22.4.2021 o 11:00 (in English)
MS Teams Link