Evaluation of mineralization in serpentinite and enclosing marks in the Hamdah area, Kingdom of Saudi Arabia (original) (raw)
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Iraqi Geological Journal, 2023
Sidi Bou Othmane region in the Central Jebilet is formed by a Devonian schistose series. The polyphase Hercynian deformation in this area is characterised by penetrative, subvertical, synmetamorphic schistosity (S1), accompanied by folding. Syntectonic granitic intrusions, hidden in the Sidi Bou Othmane region, is marked by a contact of metamorphism, which responsible for the replacement phenomena observed essentially in the limestones of the region which are transformed into graphitic Sn-W exoskarns. Syntectonic, skarnification is polyphase : (i) prograde stage (T= 500-750°C) : with graphite, garnets, idocrase, pyroxene, wollastonite, quartz, scheelite and molybdenite, crossed by a network of successive veins (garnet, idocrase, wollastonite, quartz and calcite; (ii) retrograde stage (T= 400-500°C): with garnet, idocrase, pyroxene wollastonite, quartz, calcite, epidote scheelite and cassiterite; (iii) hydrothermal alteration stage (T ≤400°C) : with sericite and clay accompanied by abundant scheelite and cassiterite, favoured by the high oxidation rate. Therefore, they would have formed in a reduced environment, in relation to large batholiths or stocks of quartz diorites and/or granites in syn, late-to post-orogenic to anorogenic contexts, in the absence of any cogenetic volcanism. The economic mineralisation of graphite was formed mainly during prograde stage, under reducing conditions. It was formed by devolatilization of a bituminous origin linked to the reef limestones and organic matter, trapped in the shales according to the following reaction: CH4 + CO2 --> 2H2O + C2
Formation and mineral chemistry of a calcic skarn from Al-Madhiq, SW Saudi Arabia
Chemie der Erde - Geochemistry, 2006
A newly identified skarn occurrence is described from the Neoproterozoic rocks of the SW Arabian shield. It is exposed to the SE, E and NE of the Al-Madhiq town. The skarn attributes correspond to those typical of the calcic skarns that host W-deposits. It is characterized as an exoskarn of the proximal type, related to a granitoid contact close to an impure quartzite bed within the regional metamorphic rocks of mixed sedimentary and volcanic derivation. The skarn is localized along a shear zone parallel to the regional faults and other major shear zones. Samples from the studied area contain characteristic skarn minerals that include both the prograde (brownish red grossular, ferrosalite, aluminian titanite-grothite, albite-oligoclase, scapolite), and retrograde (epidote, quartz, hornblende, calcite) assemblages. The pyroxenes are ferrosalites, Mn-bearing, and more like those from ''oxidized'' skarns; although garnets indicate it to be a ''reduced'' type skarn. Epidote mimicks that from typical skarns, as it bears a pistacite content of 15.9-20.7%. Grossular composition reflects a largely reduced genetic environment; as it is in solid solution with 6.5-21.6% andradite, 0-0.15% uvarovite, 0-0.47% pyrope, 4.33-18.75% almandine, and 0.4-8.58% spessartine molecules. Titanite composition varies from aluminian titanite to grothite, that may be analogous to the newly described Al-rich titanite from the low-pressure calc-silicate rocks.
Tourmaline deposit in Sikait area (Southern Eastern Desert of Egypt [SEDE]) is closely associated with metapelitic schistose rocks that belong to Neoproterozoic time. The distribution of tourmaline was mostly controlled by Nugrus shearing, along with schist leucocratic rock varieties (leucogranite, pegmatite, and aplite dikes), which are syntectonically dissected by hydrothermal quartz veins. Local concentrations of tourmaline occur either as discontinuous tourmalinite bands/pockets or as disseminated isolated clusters of crystals within the metapelitic schistose rocks, pegmatites, and quartz veins. Chemical and mineralogical changes accompanying with tourmaline formation have been observed within the schistose rocks in contact with a pegmatitic bodies in Sikait area. Four mineral assemblages were identified on approaching to the pegmatite contact: (1) Quartz-Biotite-Potassium Feldspar-Chlorite assemblage (Q-B-K-C); (2) Quartz-Biotite-Tourmaline-Chlorite assemblage (Q-B-T-C); (3) Tourmaline-Quartz-Muscovite assemblage (T-Q-M); and (4) Tourmaline-Quartz assemblage (T-Q). Toward the pegmatite contact , K, Li, Rb, SiO 2 , CaO, MgO, Sr, and Ba are decreased, while Al 2 O 3 , B 2 O 3 , Na 2 O, Fe (tot), Zr, Y, and Th are moderately increased. Variations in the mineral assemblages and whole-rock chemistry within the four alteration zones appear to be controlled by boron metasomatism and potash leaching. The normalized rare earth element patterns of rock samples from the four alteration zones suggest a partial alteration of the original sedimentary patterns by the metasomatic-magmatic fluids. The alteration could be either a single phase of interactions between pegmatite fluid and schists with B-, Li-, Rb-carrying fluid or a couple of phases (B-, Mn-, Be-rich fluid and Rb-, Li-, K-rich fluid). In all cases, boron from the pegmatite-associated fluids reacts with the surrounding schistose rocks to breakdown of sheet silicate which acts as "traps" for Rb, Sr, Li, Ba, and K and hence leads to tourmaline-rich assemblages.
Journal of Archaeological Science: Reports, 2019
As part of a current archaeological project focusing on the Azraq Basin, through notably the excavation of the Early-Middle Epipalaeolithic site of Kharaneh IV, a geoarchaeological analysis was started to ultimately characterize the chert types exploited by the inhabitants of the site and to assess their geographical origins. In order to examine prehistoric lithic procurement strategies, a detailed study of the geological literature and maps of a 3000 km 2 area surrounding the site was completed. This study revealed the presence of three chert-bearing formations dated to the Late Cretaceous and Early Tertiary in that territory: Muwaqqar Chalk-Marl Formation, Umm Rijam Chert-Limestone Formation, and Wadi Shallala Chalk Formation. A geo-archaeological survey followed. This survey comprised detailed observations about these silicifications in their sedimentary context and the collection of chert samples in both primary and secondary deposits. This contribution presents the main results of this work. The multiplicity of outcrops and the conditions of embeddedness of the siliceous horizons, on the one hand, and the characteristics of these silicifications (size, shape, quality, etc.), on the other hand, all contribute to illustrate the rich lithic potential of this region. Thus the Kharaneh IV inhabitants had access to a wide range of cherts from which to choose their stone tool kit. Given that the Epipalaeolithic tool kit of the Kharaneh IV inhabitants was based on small size tools, quite small nodules would have been sufficient for these populations to develop their lithic industry, so chert outcrops with both small and large nodules were taken into account in this study. Furthermore we present some observations on the textural, micropalaeontological, petrographical and geochemical characterization of some 104 samples of geological siliceous rocks. Such a dataset will constitute the most reliable reference in the comparison with the archaeological lithic assemblages exhumed at the site. We may already mention that the diversity of chert types documented in the geological reference collection is also present in the archaeological assemblages. Most of these lithic types are thus present in the local environment (< 15 km away). Moreover differences in raw material selection, procurement and exploitation are already noticeable between the Early and Middle Epipalaeolithic occupations that will need to be further documented and quantified. remarkable domestic structures (i.e. huts with living floors and hearths), along with bone tools, grinding stones, perforated shells, and several human burials. These remains were dated to the Early (Kebaran) and Middle (Geometric Kebaran) Epipalaeolithic (Muheisen, 1988a, b). Renewed excavations, as part of the Epipalaeolithic Foragers in Azraq Project (EFAP), directed by Jay Stock, Lisa Maher, and Tobias Richter, started in 2006 (see Maher et al., 2007). Besides the Kharaneh IV excavations in May-June 2010, we conducted a geoarchaeological survey focusing on the recognition and
The metapelitic schists of Jandagh or simply Jandagh metapelites can be divided into four groups based on mineral assemblages: (1) quartz–muscovite schists, (2) quartz–muscovite–biotite schists, (3) gar net–muscovite–chlorite schists, and (4) garnet–muscovite–staurolite schists. The Jandagh garnet–musco vite–chlorite schists show the first appearance of garnets. These garnets contain 58–76% almandine, 1–18% spessartine, and 8–20% grossular. Microprobe analysing across the garnets demonstrates an increase in Mg# from core to rim. This is a feature of the prograde metamorphism of metapelites. Wellpreserved garnet growth zoning is a sign that metapelites were rapidly cooled and later metamorphic phases had no effect here. The appearance of staurolite in garnetmuscovitechlorite schists signifies a beginning of the amphibolite fa cies. The absence of zoning in staurolite suggests that its formation and growth during prograde metamor phism occurred at a widely spaced isograde. Thermobarometric investigations show that the Jandagh metapelites were formed within a temperature range of 400–670°C and pressures of 2.0–6.5 kbar. These re sults are in agreement with the mineral paragenetic evidence and show the development of greenschist and amphibolite facies in the area studied.
Petrology and Geochemistry of Ghoshchi Batholith, NW Iran
2010
The Ghoshchi batholith, ~150 km 2 in size is a granitoidic pluton, which intruded the Permian country rocks, in Sanandaj-Sirjan Zone, NW Iran. This granitoidic pluton is covered by Oligocene-Miocene sedimentary rocks known as Qom Formation. The Ghoshchi batholith comprises five plutons with following compositions: (a) gabbro-diorite (b) biotite granite, (c) alkali granite, (d) syenites, and (e) aplitic dikes. Gabbro-diorites are the oldest intrusive unit and have interaction zone with biotite granites. These rocks have within-plate tholeiitic nature. Graphic, microgranophyric, and perthitic textures can be found in alkalifeldspar granites, indicate their shallow emplacement depth and hypersolvus nature. Alkali-feldspar granites geochemically are high-k alkaline, metaluminous to mildly peralkaline. The alkali-feldspar granitic rocks contain lower Al 2 O 3 , CaO, Fe 2 O 3 , TiO 2 , Ba, Rb, and Sr but higher SiO 2 , Na 2 O, K 2 O, Nb, Th, Y and Zr than biotite granites samples. Alkali-feldspar A-type within-plate granites were presumably formed by high degree of fractional crystallization of mantle derived mafic magmas. Plagioclase and amphibole are two main fractionated minerals. The Alkali-feldspar granites fall into the A 1 group (mantle derived) suggesting an anorogenic tectonic setting. Biotite granites and syenites are peraluminous and have crustal source.
Journal of African Earth Sciences (1983), 1986
The post-tectonic Sidarah monzogranite is composed of metaluminous to peraluminous, mediumgrained, porphyritic biotite monzogranite. N-trending quartz veins containing disseminated pyrite and molybdenite and with a Mo-Bi-Pb-Ag metallic signature occur within a 2.5 by 7 km area in the north of the pluton, close to a major Najd fault. Mineralization was controlled by three interacting factors: (1) the magmatic evolution of the intrusion, which resulted in the formation of a metalliferous hydrothermal residuum; (2) the production of deep, penetrating fractures in the outer shell of the granite as a consequence of brittle deformation associated with Najd faulting; and (3) the introduction of meteoric waters through the fracture system, which facilitated the transportation and deposition of metals within the fissure vein system.
Mineralogy and Petrology, 2004
Dykes of carbonate rocks, that cut gneisses in the Lowder-Mudiah area of southern Yemen, consist of dolomite and=or calcite with or without apatite, barite and monazite. Petrographic observations, mineralogical, XRF and ICP-MS analyses reveal that some of the carbonate rocks are derived from sedimentary protoliths, whereas others are magmatic calcio-and magnesio-carbonatites some of which are mineralized with barite-monazite. The interbanded occurrence and apparent contemporary emplacement of these different rock types within individual dykes, backed by Sr-Nd isotope evidence, are interpreted to show that intrusion of mantle-derived carbonatite magma was accompanied by mobilization of crustal marbles. That took place some 840 Ma ago but the REE-mineralization is dated at ca. 400 Ma. Ã Supplementary material to this paper is available in electronic form at http:==dx.doi.org=10.1007=s00710-004-0056-2 106 M. J. Le Bas et al. groups distinguished by geochemistry (Table 7). @ UMS Um Sallamiah; ARA Al-Arakbi; DUR Durib. Position in dyke: c centre, m mid-way, e edge. # Nd and Sr isotope data in addition to XRF and ICP data. Rocks of petrographic type A mostly belong to geochemical groups 1 and 2, type B to group 3, and type C to group 4. Exceptions BY26A and 47A are discussed in the text The carbonatite-marble dykes of Abyan Province 107 110 M. J. Le Bas et al. The carbonatite-marble dykes of Abyan Province 125 126 M. J. Le Bas et al.
2010
The Wadi Ash Shu'bah quadrangle, located in the north-central part of the Arabian Shield, is underlain by nine Precambrian volcano-sedimentary formations and a wide compositional range of Precambrian intrusive rocks. Late Proterozoic to early Paleozoic rocks of the Jibalah Group crop out in the southwestern part of the quadrangle. Paleozoic and younger units are limited to the early Paleozoic Siq Sandstone that crops out in the northwestern part of the quadrangle and small outcrops of Cenozoic basalt and unconsolidated Quaternary sediments. The Hulayfah group, dated at older than 738 Ma, is the oldest volcano-sedimentary unit in the quadrangle and consists of metamorphosed basaltic to andesitic volcanic and subvolcanic rock, and interbedded limestone, sandstone, and silicic volcanic rock. The Maraghan formation is composed of strongly folded, fine-grained sedimentary rock that was deposited between 677 and 621 Ma. The Hadn and Hibshi formations are composed of rhyolitic to rhyodacitic volcanic rock and interbedded continental sedimentary rock that were deposited between 651 and 600 Ma, but are inferred to postdate the Maraghan formation because they are significantly less deformed. Andesitic flows and volcanic breccia in the southeast corner of the quadrangle are mapped as the Jurdhawiyah group; these rocks unconformably overlie the Maraghan formation. The Zarghat formation is a thick sequence of interbedded sedimentary rock and silicic volcanic rock, and unconformably overlies the Hadn formation. It is inferred to have been deposited between 600 and 580 Ma. The Precambrian igneous rocks are organized into four tentative magmatic episodes. Greenstone of the Hulayfah group and dioritic intrusive rocks represent the oldest episode, and are believed to have formed in an ensimatic magmatic arc environment. These rocks were intruded during a second magmatic episode by post-Hulayfah monzogranite and granodiorite. A still younger, post-Hadn magmatic episode is represented by alkali-feldspar granite and syenogranite. The most recent magmatic episode is represented by small diabase and gabbro intrusions that are inferred to have been emplaced during a period of crustal rifting coincident with the deposition of the Jibalah group. The magnesite deposit near the village of Zarghat is the most significant mineral deposit in the quadrangle. However, the Hulayfah group has the most potential for metallic deposits in the area as it contains numerous gossans and ancient mine workings.