scholarly journals Mineral associations and their distribution in hydrothermal alteration zones of the Chelopech high-sulphidation deposit, Bulgaria

2017 ◽  
Vol 46 (2) ◽  
pp. 11-16
Author(s):  
Sylvina Georgieva
Keyword(s):  
Hydrothermal Alteration ◽  
Hydrothermal Fluids ◽  
Alteration Zones ◽  
Acid Sulphate ◽  
Mineral Associations ◽  
Mineral Assemblages ◽  
Hydrothermal Alteration Zones ◽  
Hydrothermal Environment ◽  
Host Rocks

This study is focused on the mineral assemblages developed during hydrothermal alteration in the host rocks of the Chelopech deposit and aims to reveal some characteristics of ore-forming fluids. Three well-distinguished and simultaneously formed hydrothermal alteration zones, characterized by specific mineral associations, occur in the area: advanced argillic, sericitic and propylitic. The presence of silica residue localities in the advanced argillic zone marks the major channels of hydrothermal fluids and indicates participation of extremely acid fluids. The existence of alunite and zunyite in the alteration indicates development of acid-sulphate hydrothermal environment, with presence of F in the fluid, which is considered to be an important feature of ore-bearing high-sulphidation epithermal systems. Dickite in association with alunite in the upper levels of the deposit suggests temperature of formation 200–250 °C. The highest temperature in depth is limited up to 375 °C, considering the occurrence of zunyite, pyrophyllite and dickite.

scholarly journals PLUMBIAN "ALUNITES" IN HYDROTHERMAL ALTERATION ZONES OF EPITHERMAL AND PORPHYRY TYPE MINERALIZATIONS IN W. THRACE

2004 ◽  
Vol 36 (1) ◽  
pp. 492 ◽  
Author(s):  
Π. Βουδούρης ◽  
Κ. Αρίκας ◽  
Α. Κατερινόπουλος
Keyword(s):  
Hydrothermal Alteration ◽  
Solid Solutions ◽  
Mineral Chemistry ◽  
Alteration Zones ◽  
Hydrothermal Alteration Zones ◽  
Hydrothermal Environment

In this study a new occurrence of Pb-rich members of the alunite supergroup minerals is described. The "alunites" were traced in advanced argilic alteration zones of epithermal and porphyry type mineralizations in W. Thrace/(Greece). These "alunites" are Ca-Sr-Ba-Pb-rich phosphatessulfates and represent solid solutions between members of the alunite, woodhouseite and crandallite group minerals. The highest concentrations of PbO in the Mavrokoryfi and Melitaina alunites are 24.7% and 17.4% respectively. The plumbian phosphates-sulfates occur in the cores of the crystals and are surrounded by common K-Na-rich alunites in Mavrokoryfi and Ba-rich woodhouseite in Melitena, an indication that they were formed in a magmatic-hydrothermal environment after dissolution of apatite and feldspars by phosphate-sulphate rich solutions. The mineral-chemistry of these "alunites" can provide information regarding the genesis of the advanced argilic alteration zones in Greece, and help us in the distinction of the epithermal from deep porphyry style environments.

scholarly journals Rhenium - rich molybdenites in Thracian porphyry Mo±Cu occurrences, NE - Greece

2001 ◽  
Vol 34 (3) ◽  
pp. 1015 ◽  
Author(s):  
Β. ΜΕΛΦΟΣ ◽  
Π. ΒΟΥΔΟΥΡΗΣ ◽  
Κ. ΑΡΙΚΑΣ ◽  
Μ. ΒΑΒΕΛΙΔΗΣ
Keyword(s):  
Chemical Composition ◽  
Hydrothermal Alteration ◽  
Fluid Inclusions ◽  
Mineral Chemistry ◽  
Rare Element ◽  
Alteration Zones ◽  
Porphyry Cu ◽  
Mineral Assemblages ◽  
Host Rocks

The present study correlates both the mineralogy of the hydrothermal alteration and the mineral chemistry of molybdenites from three porphyry Mo ± Cu occurrences in Thrace: Melitena, Pagoni Rachi/Kirki and Ktismata/ Maronia. The mineralisations are genetically related to calcalkaline, subvolcanic bodies of Tertiary age. According to their mineralogical and chemical composition the host rocks are characterized as dacite (Melitena), dacitic andésite (Pagoni Rachi) and porphyry microgranite (Ktismata/Maronia). The molybdenites occur in disseminated form, as fracture fillings, as well within quartz stockworks crosscuting the central alteration zones of the intrusives. They are accompanied by the following mineral assemblages: quartz, sericite, pyrophyllite, diaspore, Ca-Ba-rich alunite, pyrite (Melitena); quartz, albite/K-feldspar, biotite, actinolite, magnetite (Pagoni Rachi); and sericite, kaolinite, pyrophyllite, chlorite (Ktismata). Preliminary microthermometric results showed homogenisation temperatures from 352° to 390 °C for Pagoni Rachi area and from 295° to 363 °C for Melitena area. The salinities range between 4.5 and 6.1 wt% eq. NaCl and between 2.7 and 3.4 wt% eq. NaCl, respectively. Detailed study on over 400 fluid inclusions from the porphyry Cu-Mo deposit in Maronia area revealed formation temperatures from 300° to 420 °C, whereas salinities are distincted in two different groups from 6 to 16 wt% eq. NaCl and from 28 to 55 wt% eq. NaCl. The chemical composition of the molybdenites from the three porphyry Mo±Cu deposits in Thrace was studied with 155 microprobe analyses. The results revealed unusual high and variable Re concentrations in the studied molybdenites. Re content in molybdenite from Melitena area vary from 0.21 to 1.74 wt%, 0.79 wt% on average. The highest values were measured in samples from Pagoni Rachi (0.45-4.21 wt%, 1.98 wt% on average). Finally, microprobe analyses from molybdenite in Ktismata/Maronia showed Re content between 0.12 and 2.88 wt% (0.76 wt% on average). Rhenium is a very rare element with many definite uses, and is mainly associated with molybdenite in porphyry type deposits. According to the data published so far the Re content in molybdenite reaches up to 0.42 wt%. It is obvious therefore that such high Re concentrations (0.12 to 4.22 wt%) from the studied molybdenites in Thrace, are very ineresting for a possible future exploitation.

scholarly journals HYDROTHERMAL ALTERATION AND MINERALIZATION OF THE PETROTA EPITHERMAL SYSTEMS (W.THRACE, GREECE)

2004 ◽  
Vol 36 (1) ◽  
pp. 369 ◽  
Author(s):  
Κ. Μιχαήλ ◽  
Μ. Δημήτρουλα
Keyword(s):  
Hydrothermal Alteration ◽  
Hydrothermal Systems ◽  
Alteration Zones ◽  
Epithermal System ◽  
Argillic Alteration ◽  
Ore Mineralization ◽  
System 2 ◽  
Advanced Argillic Alteration ◽  
Hydrothermal Alteration Zones ◽  
Host Rocks

At the Petrota graben important epithermal zones are developed. On the basis of the mineral assemblages of alteration zones and the type of the host rocks, the epithermal zones can be grouped into three epithermal systems: 1. Perama epithermal system 2. Mavrokoryfi epithermal system and 3. Othondoto epithermal system Hydrothermal alteration zones are developed within volcanoclastic rocks - epiclastic sandstones, andésite tuffs (Perama epithermal system), hyaloclastites (Mavrokoryfi) and rhyolitic rocks (Othondoto). Silicification (in various types) and advanced argillic alteration are the most important alteration zones and are established on the largest scale. Ore mineralisation occurs as veins, veinlets in silicification zones or secondary mineralisation in the supergene zone (Perama epithermal system). Disseminated ore mineralization is also found in the silicification zone at Othondoto and Mavrokoryfi epithermal systems. Based on the geological environment, the type of hydrothemal alteration zones (silicification and advanced argillic alteration) and the mineral compositon of the ore (enargite- luzonite), the hydrothermal systems of Petrota graben can be referred as high sulfidation systems.

scholarly journals A Remote Sensing-Based Application of Bayesian Networks for Epithermal Gold Potential Mapping in Ahar-Arasbaran Area, NW Iran

2019 ◽  
Vol 12 (1) ◽  
pp. 105 ◽  
Author(s):  
Seyed Mohammad Bolouki ◽  
Hamid Reza Ramazi ◽  
Abbas Maghsoudi ◽  
Amin Beiranvand Pour ◽  
Ghahraman Sohrabi
Keyword(s):  
Remote Sensing ◽  
Bayesian Network ◽  
Hydrothermal Alteration ◽  
Gold Mineralization ◽  
Epithermal Gold ◽  
Alteration Zones ◽  
Mineral Potential ◽  
Potential Map ◽  
Bayesian Network Classifier ◽  
Hydrothermal Alteration Zones

Mapping hydrothermal alteration minerals using multispectral remote sensing satellite imagery provides vital information for the exploration of porphyry and epithermal ore mineralizations. The Ahar-Arasbaran region, NW Iran, contains a variety of porphyry, skarn and epithermal ore deposits. Gold mineralization occurs in the form of epithermal veins and veinlets, which is associated with hydrothermal alteration zones. Thus, the identification of hydrothermal alteration zones is one of the key indicators for targeting new prospective zones of epithermal gold mineralization in the Ahar-Arasbaran region. In this study, Landsat Enhanced Thematic Mapper+ (Landsat-7 ETM+), Landsat-8 and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) multispectral remote sensing datasets were processed to detect hydrothermal alteration zones associated with epithermal gold mineralization in the Ahar-Arasbaran region. Band ratio techniques and principal component analysis (PCA) were applied on Landsat-7 ETM+ and Landsat-8 data to map hydrothermal alteration zones. Advanced argillic, argillic-phyllic, propylitic and hydrous silica alteration zones were detected and discriminated by implementing band ratio, relative absorption band depth (RBD) and selective PCA to ASTER data. Subsequently, the Bayesian network classifier was used to synthesize the thematic layers of hydrothermal alteration zones. A mineral potential map was generated by the Bayesian network classifier, which shows several new prospective zones of epithermal gold mineralization in the Ahar-Arasbaran region. Besides, comprehensive field surveying and laboratory analysis were conducted to verify the remote sensing results and mineral potential map produced by the Bayesian network classifier. A good rate of agreement with field and laboratory data is achieved for remote sensing results and consequential mineral potential map. It is recommended that the Bayesian network classifier can be broadly used as a valuable model for fusing multi-sensor remote sensing results to generate mineral potential map for reconnaissance stages of epithermal gold exploration in the Ahar-Arasbaran region and other analogous metallogenic provinces around the world.

Detection of pre-defined boundaries between hydrothermal alteration zones using rotation-variant template matching

2008 ◽  
Vol 34 (12) ◽  
pp. 1815-1826 ◽  
Author(s):  
Frank J.A. van Ruitenbeek ◽  
Harald M.A. van der Werff ◽  
Kim A.A. Hein ◽  
Freek D. van der Meer
Keyword(s):  
Hydrothermal Alteration ◽  
Template Matching ◽  
Alteration Zones ◽  
Hydrothermal Alteration Zones
Sign in / Sign up

Export Citation Format

Share Document