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Design and construction of an LPG rock cavern near by an existing LPG rock storage
Published in Bjørn Nilsen, Jørn Olsen, Storage of Gases in Rock Caverns, 2022
With the exception of crush zones, the bedrock is fresh and unweathered. In zones with strong crushing, however, the bedrock has usually been more or less altered to chlorite and clay minerals. In minor zones the mineral alteration is limited to single fractures filled with clay.
Water/Rock Interactions
Published in William J. Deutsch, Groundwater Geochemistry, 2020
The mineralogy of the subsurface and the general process of mineral alteration in response to chemical weathering were discussed in Section 1.3. The following section describes mineral equilibrium and solubility in the aquifer environment.
Uranium Transport in the Sub-Surface Environment Koongarra - A Case Study
Published in Herbert E. Allen, E. Michael Perdue, David S. Brown, Metals in Groundwater, 2020
The weathered zone clays and iron minerals in the vicinity of the Koongarra ore deposit form, at least in part, by alteration of chlorite, the major rock-forming mineral of the quartz-chlorite schist [17]. Dibble and Tiller [18] note that the authigenic, or secondary minerals, formed by water-rock interaction (i.e. the alteration products) are usually metastable with the attainment of equilibrium delayed by as much as 107 years. The relationship between mineral alteration and transport of transuranic elements (mediated by processes such as adsorption and desorption) is likely to be strongly influenced by the mechanism and kinetics of alteration.
Improving geological logging of drill holes using geochemical data and data analytics for mineral exploration in the Gawler Ranges, South Australia
Published in Australian Journal of Earth Sciences, 2021
E. J. Hill, A. Fabris, Y. Uvarova, C. Tiddy
More subtle mineral alteration affects many of the units intersected by MSDP11. Zones of weak pervasive sericite and chlorite alteration are common but do not result in significant chemical variation and therefore are not classified as separate units. Where alteration intensity increases, such as between 260 and 290 m, associated with a zone of chloritised metamorphic biotite within the meta-diorite (Fabris et al., 2017), a distinct sub-domain is evident at a scale of ∼4. However, it is unclear whether changes in Fe, K, Ca and Ti across this interval are directly related to mineral alteration or subtle primary lithological variation. Another form of mineral alteration overprint on primary lithology is the effect of weathering. Weathering involves the chemical breakdown of rocks owing to near-surface processes and is a common overprint that can result in significant chemical modification and therefore make it difficult to differentiate from lithological change (e.g. McQueen & Scott, 2008). In drill hole MSDP11, weathering mainly effects a felsic igneous protolith and results in primary feldspar being replaced by kaolinite to varying degrees down to a depth of 74.5 m. This weathering effect is mapped chemically by a progressive reduction in K and the near total removal of Ca (Figure 17). Even the immobile elements Ti and Nb show some modification. Weathering results in a distinct domain at a scale of ∼40 (between 30 and 70 m); however, confidently distinguishing change owing to weathering rather than primary lithological difference remains a challenge.
Investigation based on quantified spatial relationships between gold deposits and ore genesis factors in northeast Malaysia
Published in Journal of Spatial Science, 2021
Mathew Gregory Tagwai, Onimisi A. Jimoh, Kamar Shah Ariffin, Mohd Firdaus Abdul Razak
The identification of ore genesis factors and linking them with the available data requires understanding of the processes and their timing within the geodynamic history of the area (Mccuaig et al. 2010, Joly et al. 2012b). The aspects of linking datasets with targeted criteria are in three important steps. The first step (starting stage of the exploration) is the critical understanding of the mineral system. At this stage, all the critical processes such as the source (magma, heat), the migration pathways (structures) and depositional environment (host rock) leading to the formation of the orogenic gold deposits are established. The second step is the understanding of the deposition mechanism. Orogenic gold has a distinct deposition mechanism of fluid mixing, the pressure to temperature change of the mineralizing fluid (P-T change) and wall-rock reaction processes (Goldfarb and Groves 2015b). At this stage, all the mechanisms leading to the deposition of gold are established. The third step is to establish and link reflecting elements to available geospatial data. The reflecting elements such as critical structures (lineaments), alteration minerals and rock geochemistry are the geological features indicating the deposition mechanism. Some of the available data may include traditional geological maps and remote sensing images. For example, remote sensing images can allow the extraction of lineaments and mineral alteration zones. The fourth step is to quantify the spatial relationship between the factors.
Mineralogy and character of the Liikavaara Östra Cu-(W-Au) deposit, northern Sweden
Published in GFF, 2020
Mathis Warlo, Christina Wanhainen, Olof Martinsson, Peter Karlsson
The wall and host rock in Liikavaara are strongly altered by biotitisation, sericitisation, and chloritisation. This can partly be explained by mineral alteration of e.g. primary pyroxene, amphibole, feldspar, and biotite. However, chemical data suggests an additional influx of potassium to the host rock and dykes (Fig. 6B). Also, the occurrences of veins rich in quartz, calcite, tourmaline and sulphides need an external source to explain the high contents of Si, Ca, B and metals. Sammelin et al. (2011) interpreted the Cu-mineralisation to be related to saline and CO2-bearing fluids. This and a weak dissemination of sulphides in the aplite dykes and the footwall intrusion possibly suggest magmatic-hydrothermal fluids (Roedder 1971; Nash 1976; Richards 2011) derived from the degassing granodiorite intrusion and aplite dykes. The high density of mineralised veins, especially in proximity to the dykes, supports an idea of the fracture system related to the dyke emplacement to have acted also as major pathways for these magmatic-hydrothermal fluids to ascend and penetrate the surrounding rocks.