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Magmatism and Geodynamics in the Archaean
Published in O.A. Bogatikov, R.F. Fursenko, G.V. Lazareva, E.A. Miloradovskaya, A. Ya, R.E. Sorkina, Magmatism and Geodynamics Terrestrial Magmatism Throughout the Earth’s History, 2020
In the Late Archaean Olondo greenstone belt, among the tonalite–trondhjemitic gneisses, the same two units can be recognized with certainty: a lower one, 500 m thick, composed predominantly of basic and ultrabasic volcanics and an upper one, 600 m thick, composed of intermediate and acid volcanics and a subordinate quantity of sediments. Subvolcanic sill-shaped bodies of basic and ultrabasic composition are present. Komatiites and basalts occur as both massive and differentiated flows and pillow lavas (Fig. 6.6). The results of chemical analyses for typical rock varieties are given in Tables 6.5 and 6.6. As is the case for the Tungurcha greenstone belt, two types of komatiites can be distinguished here: Al-depleted and Al-undepleted; however, the latter predominate. Among these, in turn, there are two distinctive groups of rocks. The first group are enriched in Zr relative to Ti and Y, and in La relative to Sm, that is, in elements accumulated in the Earth’s crust (LREE-rich komatiites), suggesting their contamination by crustal material. The second group are strongly depleted in incompatible elements relative to moderately incompatible (komatiites depleted in LREE). The basalts that are associated with the komatiites are represented by olivine- to quartz-normative varieties, as within the Tungurcha belt. In contrast to Early Archaean ones, they are characterized by relatively high concentrations of FeO, Ni, Co and Cr and are distinguished by their severe depletion in highly incompatible elements.
Mineralogy of various types of Th-U-REE mineralisation in the iron oxide – apatite deposits of the Bafq district, Central Iran
Published in Applied Earth Science, 2023
Khalegh Khoshnoodi, Samaneh Ziapour, Mohammad Yazdi, Michel Cuney
REE-U-Th mineralisation occurs in the Saghand Anomaly No.5 and is associated with alkali-metasomatism. Alkali-metasomatism and mineralisation are controlled by fault zones. The metasomatic zones extend from unaltered subvolcanic diorite and quartz diorite host rocks to albite, actinolite and phlogopite metasomatites, and ultimately to magnetite orebodies (Figure 12). In the Saghand Anomaly No.5, davidite is the most abundant host mineral of REE, Y and U (Figure 12(a)). Thorite is the host mineral of Th, together with lesser amounts of REE, Y and U. Thorite occurs as inclusions within the actinolite crystals in albite-actinolite assemblages during the Na–Ca metasomatic stage. The total amount of REE(+Y)2O3 in davidite is between 12.67 and 18.77 wt-% (Table 8).
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
The geologic map of the Parkam exploration district was prepared based on detailed field studies (Figure 4). According to observations, a set of volcanic rocks accompanied by recent unconsolidated sediments comprise the host to the subvolcanic body and associated porphyry copper mineralisation in the Parkam exploration district. The volcanics vary from mafic to felsic, but are mostly intermediate in composition and include andesitic volcanic rocks, basaltic to andesitic lavas, and andesitic pyroclastic rocks widespread in the area (Figures 4 and 5(a)). These lithological units are intruded by diorite dykes (Figure 3(d)) and subvolcanic bodies of diorite and micro quartz-diorite (Figures 3(c) and 4) which are associated with alteration system (see the next section; see also Tangestani and Moore 2001). The latest stage of magmatism was accompanied by the emplacement of the dacite dome in the northwestern part of the district (Figure 3(b)).
Investigation on the morphological and mineralogical properties of coarse aggregates under VSI crushing operation
Published in International Journal of Pavement Engineering, 2021
Chonghui Wang, Hainian Wang, Markus Oeser, Mohd Rosli Mohd Hasan
Three different types of particles, namely, granite aggregates originated from Fujian, diabase aggregates originated from Guangdong, and limestone aggregates from Guangxi were chosen for this study, as depicted in Figure 2, since they are commonly used as construction materials in China for pavement engineering. Granite is one typical intrusive igneous grain which mainly consists of quartz, feldspar, chlorite, and biotite. Diabase is determined as subvolcanic rock or shallow intrusive rock, which equivalent to plutonic gabbro. Limestone is one sort of sedimentary rocks which mainly developed by skeletal fragments of marine creatures, and like other sedimentary rocks, limestone dominantly composed of calcium carbonate. Polishing stone value measurements revealed that the PSV of granite is 57, and that of diabase and limestone is 61 and 32, respectively.