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Mineral exploration
Published in Odwyn Jones, Mehrooz Aspandiar, Allison Dugdale, Neal Leggo, Ian Glacken, Bryan Smith, The Business of Mining, 2019
Odwyn Jones, Mehrooz Aspandiar, Allison Dugdale, Neal Leggo, Ian Glacken, Bryan Smith
An example of the minerals system approach is one for orogenic gold type deposits (Figure 2.2). The trigger or energy for the system is acquired due to high heat flow and fluid flux from the mantle into the overlying crust. The source of fluids is either the mantle, magmas, metamorphic fluids or seawater, or meteoric water (hydrosphere waters). These fluids react with rocks along their path, scavenge metals and carry these metals upwards through conduits, which are crustal scale faults, structural domes or strati-graphic aquifers. The metal-bearing hydrothermal fluids encounter traps, which are physical barriers that cause the metals to be dropped or crystal-lised into minerals due to a change or drop in temperature of the fluid, the mixing of fluids or the reaction of the fluid with a rock. The reaction of the hydrothermal fluids with near-surface crustal rocks alters the rock and is known as hydrothermal alteration. This alteration concentrates the ore metals and minimises leakage of metals.
Resources, geochemical features and environmental implications of the geothermal waters in the continental rift zone of the BüYüK Menderes, Western Anatolia, Turkey
Published in Jochen Bundschuh, Barbara Tomaszewska, Geothermal Water Management, 2018
At the surface, the metamorphic and sedimentary rocks in the geothermal fields of the rift zone of the Büyük Menderes, at very important localities such as Kızıldere, Salavatli, Germencik and others, are intensively altered. This is recognizable in a distinct color change of the rocks, studies of rock microscopy on various thin sections, and X-ray diffractometry analyses. The hydrothermal alteration is distinguished by phyllic, argillic, and silicic ± haematization zones. The phyllic and argillic alteration zones occur in the Paleozoic metamorphic rocks, whereas silicic ± haematization alteration zones are an overprinting type and are observed in Paleozoic metamorphic and sedimentary rocks. In addition, a new alteration type of carbonatization has been recognized in sedimentary rocks that can be observed in the geothermal fields of Kızıldere in particular (Özgür and Pekdeğer, 1995). Due to high temperature, pressure, and CO2 content in the geothermal water reservoir of the study area, high-temperature acidic water infiltrates the soil formations and dissolves CaCO3. The solution seeks equilibrium constantly, but does not reach suitable parameters in the surrounding environment and, thus, the solution loses temperature, pressure and CO2 on its way to the surface, for which reason the pH values increase to 9.2. Consequently, the geothermal fluid is unable to retain CaCO3 in solution, which instead precipitates and occurs in sedimentary rocks near the surface. The silicic alteration zone can be observed in both Paleozoic metamorphic rocks and Miocene to Pliocene sedimentary rocks (Özgür, 1998).
Palaeozoic porphyry molybdenum-tungsten mineralisation in the Myszków area, southern Poland
Published in Adam Piestrzyński, Mineral Deposits at the Beginning of the 21st Century, 2001
M. Markowiak, J. Ślósarz, K. Lasoń, M. Podemski, Ł. Karwowski, M. A. Chaffee
The associated gangue minerals include quartz, feldspars (orthoclase, microcline, adularia, albite), chlorite, epidote, sericite, muscovite, biotite, calcite, ankerite, dolomite, barite, fluorite, and gypsum. Silicification, biotitisation, feldspathisation, sericitisation, and carbonatisation are significant types of hydrothermal alteration found in the host rocks. Other types of alteration, such as chloritisation, propylitisation, and argillisation occur only locally.
Identifying hydrothermally altered rocks using ASTER satellite imageries in Eastern Anti-Atlas of Morocco: a case study from Imiter silver mine
Published in International Journal of Image and Data Fusion, 2022
Youssef Atif, Abderrahmane Soulaimani, Atman Ait lamqadem, Amin Beiranvand Pour, Biswajeet Pradhan, El Aouad Nouamane, Kharis Abdelali, Aidy M Muslim, Mohammad Shawkat Hossain
Hydrothermal alteration minerals are proximal to several base and precious metal deposits, and its products can provide insights into the characteristics of hydrothermal systems and ore mineralisation. Hence, alteration minerals need to be identified and classified at local and regional scales (Mathieu 2018). ASTER data have been extensively used to map hydrothermal alteration minerals and zones associated with ore deposits in metallogenic provinces (Guha et al. 2019, Moradpour et al. 2020, Chattoraj et al. 2020, Bolouki et al. 2020, Shirmard et al. 2020, Wambo et al. 2020). The band ratios, principal component analysis (PCA), minimum noise fraction (MNF), spectral angle mapper (SAM), matched filtering (MF), blend-matched filtering, linear spectral mixing (LUS) and constrained energy minimisation (CEM) image processing methods have been used for processing ASTER multispectral data to map hydrothermal alteration minerals and lithological units (Cŕosta et al. 2003, Mars and Rowan 2006, Pour and Hashim 2012, Gabr et al. 2015, Testa et al. 2018, Zoheir et al. 2019a, 2019b, Pour et al. 2019a, 2019b, 2019c, 2021a, 2021b, Eldosouky et al. 2020, Bolouki et al. 2020).
Delineation of geochemical anomalies for mineral exploration using combining U-statistic method and fractal technique: U-N and U-A models
Published in Applied Earth Science, 2022
Seyyed Saeed Ghannadpour, Ardeshir Hezarkhani
Hydrothermal alteration is widespread in the Parkam area and includes propylitic, phyllic, argillic and potassic types in order of extent. The phyllic alteration constitutes the central zone of the alteration system and is associated with the potassic alteration in the east and west, as well as with the argillic alteration toward the south. The propylitic alteration surrounds the other types of alteration in the study area (Figure 6). The presence of the potassic alteration in the peripheral zone of the porphyry system (in addition to the central zone) is a characteristic of the Parkam exploration district (Figures 4 and 6). Expect for the propylitic alteration which extends mostly over the host volcanic rocks (Figure 5(b)), the other types of alteration are associated mainly with the dioritic subvolcanic body (Figures 4, 6 and 7).
Applying the combination of U-statistic and Mahalanobis distance as a multivariate structural method for the delineation of geochemical anomalies
Published in Geosystem Engineering, 2018
Seyyed Saeed Ghannadpour, Ardeshir Hezarkhani
Hydrothermal alteration is widespread in the Parkam area and includes propylitic, phyllic, argillic, and potassic types in order of extent. The phyllic alteration constitutes the central zone of the alteration system and is bordered by potassic alteration in the east and west, as well as argillic alteration toward the south. The propylitic alteration surrounds the other types of alteration in the study area (Figure 3). The presence of potassic alteration in the peripheral zone of the porphyry system (in addition to the central zone) is a characteristic of the Parkam exploration district (Figures 2 and 3). Except for the propylitic alteration which extends mostly over the host volcanic rocks, the other types of alteration are associated mainly with the dioritic subvolcanic body (Figures 2 and 3).