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The present work reports on the first evidence of a possible hypervelocity impact crater in the Sultanate of Oman. The impact origin of the structure is determined based on field observations, microscopic observations of shatter cones, planar fractures (PFs) and feather features (FFs) in quartz, calcite, and feldspar, and melt-bearing polymict breccias with various types of melts. The structure consists of an elliptical bowl-shaped ridge 750 m long and 550 m wide, oriented roughly north-northeast to south-southwest. The elliptical shape and relief asymmetry indicate an oblique collision. The precursor target lithologies include local late Proterozoic Masirah Bay siliciclastic formations, carbonate and acidic volcanic rocks of the late Precambrian Halfayn Formation, and basement rocks. The crater rim, up to 15–20 m above ground, is composed of quartzite, jasper, agate, monomict siliceous and hematite breccia, and metamorphosed shale (hornfels). An ejecta blanket composed of target rocks covers the floor, outer rim, and the area extending to the immediate northeast and east of the structure. Quaternary aeolian sand covers most of the crater surface, including the 1 to 2 m thick melt-rich polymict breccia found in the crater center. The planar fractures (PFs) and feather features (FFS) in quartz and feldspar suggest a low shock pressure between 5 and 14 GPa. Our observations are consistent with set criterions for impact crater identification, confirming the possible impact origin of the Mahout structure. [ABSTRACT FROM AUTHOR]

Mossbauer spectroscopy, [H.sub.2]O, and microprobe analysis techniques have been used to study upper mantle fcrrikaersutite megacrysts from the scoria cones of the Ash Sham alkaline volcanic field, northeastern part of the Arabian plate. Mossbauer spectra, collected at 298 K, indicate that the kaersutites are highly oxidized and all iron occurs as [Fe.sup.3+]. Two components were detected within the [Fe.sup.3+] quadrupole splitting distribution of the C-type sites and were assigned to M1 and M2-3 sites. The quadrupole splitting (QS) varies between 0.734-0.87 mm/s ([Fe.sup.3+] M1) and 1.28-1.45 mm/s ([Fe.sup.3+] M-23). The kaersutite has a large oxy component in the amphibole OH-site (1.49-1.85 [O.sup.2-] apfu) similar to the mantle-derived kaersutites. The very high ferric concentration in the kaersutites would suggest crystallization from a relatively oxidizing magma, perhaps with [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] close to the fayalite-magnetite-quartz (FMQ), and may be a function of the high [Fe.sup.3+]/[Fe.sub.tot], of the metasomatic fluid that crystallized these amphiboles. Keywords: Mossbauer, microprobe, ferrikaersutite, upper mantle, Arabian plate, oxidation, metasomatism

Copyright of Sultan Qaboos University Journal for Science is the property of Sultan Qaboos University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Carbonate precipitation through atmospheric CO2 uptake by alkaline‐hyperalkaline waters offers a potential approach to mitigating anthropogenic CO2 emissions. The Oman Ophiolite produces high‐pH water characterized by continuous sequestration of CO2 at the air‐water interface. The geochemical and isotopic data of carbonates from the Barzaman Formation is used to assess the amount of atmospheric CO2 stored in the dolomite‐calcite assemblage. Post Archean Australian Shale ‐normalized rare earth elements patterns, with the exception of La and Ce anomalies, are similar to those of the bulk oceanic and lower crusts, with increasing LREE and flat HREE trends, and a positive Eu anomaly. The δ13CVPDB and δ18OVSMOW isotope values of the analyzed samples show two distinct end‐members, in which dolomite (−7.77‰ and +27.3‰) is isotopically heavier than calcite (−9.93‰ and +21.5‰). The estimated carbonate growth temperatures (18°C–56°C) are indistinguishable from the previously reported range (18°C–66°C). The C‐O isotope model for calcite, groundwater, and atmospheric CO2 shows that an ophiolite‐derived calcite sample absorbed an unequivocal amount of atmospheric CO2 (78% ± 11%) during precipitation. At the same time, dissolved inorganic carbon (DIC) in water accounts for the remaining carbon contribution (22% ± 9%). DIC is closely associated with different carbonate lithofacies and ophiolite‐derived soil, exhibiting large variations in C‐O isotopic compositions caused by isotopic disequilibrium. Taken together, geochemical and isotopic properties confirm that the carbonates were formed under oxic conditions triggered by the water‐rock interaction. For a reliable estimate of CO2 sequestered by carbonates of the Barzaman Formation, a systematic groundwater analysis is recommended to determine the contribution of CO2 in DIC. Plain Language Summary: The sequestration of CO2 through mineralization has been a widely debated potential method for coping with rising levels of anthropogenic CO2 emissions. The C‐O stable isotope compositions of carbonates from the Barzaman Formation in Oman have been used to estimate the amount of atmospheric CO2 stored in them. These samples have geochemical signatures that suggest they are closely related to the oceanic crust, which is a precursor to the Oman Ophiolite. Based on the carbon and oxygen isotope model, we estimate that atmospheric CO2 contributed approximately 78% ± 11% (sd) of the overall carbon budget in a calcite sample at the time of its formation. The remaining 22% ± 9% (sd) of the carbon, on the other hand, is most likely contributed by DIC acquired by water after interacting with different carbonate lithofacies and soil. Additional research on local groundwater is needed to fully evaluate the C‐budget in the Barzaman Formation, as DIC may contain atmospheric CO2 previously stored by the carbonate lithofacies. Key Points: First reporting of the geochemical and isotopic data sets of carbonates from the Barzaman Formation, OmanC‐O isotope model is used to calculate the amount of atmospheric CO2 stored in carbonates as a result of carbonation of ultramafic clastsCarbonate growth temperatures in various water types are estimated using their corresponding δ18OVPDB and δ18OVSMOW values [ABSTRACT FROM AUTHOR]

This study demonstrates the use of ASTER data for the mapping of gypsum deposits and associated geological formations that occurred in the Thumrait region of southern Oman. The measurement of spectra over samples of gypsum in the 1,300–2,500 nm wavelength using a PIMA spectrometer showed the presence of distinct absorptions at 1400–1600, 1750, 1940, 2,100, and 2,400 nm characteristics to OH stretching, H2O combinations, and SO bending overtones and stretching, respectively. Studying the unique spectral absorption characters of gypsum samples, we developed a false color composite (FCC) and an image by decorrelation stretch using the spectral bands 7, 3, and 2 of ASTER. The results FCC showed the regions of gypsum occurrences, and the decorrelated image discriminated the gypsum occurrences from other geological formations of the area. The study of surface mineralogy of the region using the VNIR‐SWIR bands by the spectral angle mapper method showed the presence of sulfate, carbonate, and clay minerals of the geological formations in the study area. We compared the results of ASTER with the results obtained using spectral bands 12, 8, and 4 of Sentinel‐2A processed by the same methods. The study showed that the spectral bands of ASTER can be used for mapping the gypsum and associated geological formations. [ABSTRACT FROM AUTHOR]

The Dhofar 1673, Dhofar 1983, and Dhofar 1984 meteorites are three lunar regolith breccias classified based on their petrography, mineralogy, oxygen isotopes, and bulk chemistry. All three meteorites are dominated by feldspathic lithic clasts; however, impact melt rock clasts and spherules are also found in each meteorite. The bulk chemistry of these samples is similar to other feldspathic highland meteorites with the Al2O3 content only slightly lower than average. Within the lithic clasts, the Mg # of mafic phases versus the anorthite content of feldspars is similar to other highland meteorites and is found to plot intermediate of the ferroan‐anorthositic suite and magnesian suite. The samples lack any KREEPy signature and have only minor indications of a mare basalt component, suggesting that the source region of all three meteorites would have been distal from the Procellarum KREEP Terrane and could have possibly been the Feldspathic Highland Terrane. All three meteorites were found within 500 m of each other in the Dhofar region of Oman. This, together with their similar petrography, stable isotope chemistry, and geochemistry indicates the possibility of a pairing. [ABSTRACT FROM AUTHOR]

This study focuses on the reuse of waste ferrochrome (FeCr) slag as a partial replacement for sand in the production of cement mortar with improved thermal and mechanical properties. Sand was replaced by FeCr slag in different percentages ranging from 0 up to 20% (by weight). The flowability test was performed to evaluate the mortar's behavior in a fresh state. Tests for the compressive strength, flexural strength, drying shrinkage, thermal conductivity, and specific heat of the blended mortars have been conducted according to ASTM standards at 3, 7, and 28 days of curing. X-ray diffraction (XRD) was utilized to examine the phase composition. The scanning electron microscope (SEM) was used for inspecting the microstructure changes of the hardened samples. The results revealed considerable improvements in the compressive and flexural strengths; improvement ratios of about 33 and 39% were attained respectively at 20% FeCr slag replacement after 28 days of curing. The drying shrinkage generally decreased with increasing replacement of sand by FeCr slag. FeCr slag acts to increase both the thermal conductivity and specific heat effectively. FeCr slag caused remarkable modifications in the microstructure of the blended mortars. [ABSTRACT FROM AUTHOR]

We report the equilibration temperatures derived from the oxygen isotope thermometry of pyroxene-olivine pair from the Dar al Ghani (DaG) 476 (1200 +105/-90 °C) and Sayh al Uhaymir (SaU) 008 (1430 +220/-155 °C) meteorites showing a difference of over 200 °C at the face values. Regardless of the large associated uncertainties, contrasting geochemical and isotopic characteristics such as oxygen fugacities, hydrogen isotopic compositions (referred to as the D/H ratios), olivine abundances, presence of merrillite and/or apatite, and their chlorine contents between the two meteorites are observed in the literature. These opposing features lend support to the idea that the relative difference observed in the estimated temperatures is probably real and significant, thus providing insights into the Martian mantle magmatism. Based on our temperature estimation and previous magmatic models, we propose that SaU 008 could have been originated from a deeper depleted mantle source. However, DaG 476 may have been produced by the partial melting of the entrained pockets of the depleted mantle similar to that of the SaU 008's source at a relatively shallower depth. Both meteorites erupted as a relatively thick lava flow or a shallow intrusion at approximately the same time followed by a launch initiated by a single meteoritic impact 1.1 million years (Ma) ago. [ABSTRACT FROM AUTHOR]

Mean bulk chemical data of recently found H5 and L6 ordinary chondrites from the deserts of Oman generally reflect isochemical features which are consistent with the progressive thermal metamorphism of a common, unequilibrated starting material. Relative differences in abundances range from 0.5-10% in REE (Eu = 14%), 6-13% in siderophile elements (Co = 48%), and >10% in lithophile elements (exceptions are Ba, Sr, Zr, Hf, U = >30%) between H5 and L6 groups. These differences may have accounted for variable temperature conditions during metamorphism on their parent bodies. The CI/Mg-normalized mean abundances of refractory lithophile elements (Al, Ca, Sm, Yb, Lu, V) show no resolvable differences between H5 and L6 suggesting that both groups have experienced the same fractionation. The REE diagram shows subtle enrichment in LREE with a flat HREE pattern. Furthermore, overall mean REE abundances are ~0.6 × CI with enriched La abundance (~0.9 × CI) in both groups. Precise oxygen isotope compositions demonstrate the attainment of isotopic equilibrium by progressive thermal metamorphism following a mass-dependent isotope fractionation trend. Both groups show a ~slope-1/2 line on a three-isotope plot with subtle negative deviation in ∆17O associated with δ18O enrichment relative to δ17O. These deviations are interpreted as the result of liberation of water from phyllosilicates and evaporation of a fraction of the water during thermal metamorphism. The resultant isotope fractionations caused by the water loss are analogous to those occurring between silicate melt and gas phase during CAI and chondrule formation in chondrites and are controlled by cooling rates and exchange efficiency. [ABSTRACT FROM AUTHOR]

Dhofar 1671 is a relatively new meteorite that previous studies suggest belongs to the Rumuruti chondrite class. Major and REE compositions are generally in agreement with average values of the R chondrites ( RCs). Moderately volatile elements such as Se and Zn abundances are lower than the R chondrite values that are similar to those in ordinary chondrites ( OCs). Porphyritic olivine pyroxene ( POP), radial pyroxene ( RP), and barred olivine ( BO) chondrules are embedded in a proportionately equal volume of matrix, one of the characteristic features of RCs. Microprobe analyses demonstrate compositional zoning in chondrule and matrix olivines showing Fa-poor interior and Fa-rich outer zones. Precise oxygen isotope data for chondrules and matrix obtained by laser-assisted fluorination show a genetic isotopic relationship between OCs and RCs. On the basis of our data, we propose a strong affinity between these groups and suggest that OC chondrule precursors could have interacted with a 17O-rich matrix to form RC chondrules (i.e., ∆17O shifts from ~1‰ to ~3‰). These interactions could have occurred at the same time as 'exotic' clasts in brecciated samples formed such as NWA 10214 ( LL3-6), Parnallee ( LL3), PCA91241 (R3.8-6), and Dhofar 1671 (R3.6). We also infer that the source of the oxidation and 17O enrichment is the matrix, which may have been enriched in 17O-rich water. The abundance of matrix in RCs relative to OCs, ensured that these rocks would be apparently more oxidized and appreciably 17O-enriched. In situ analysis of Dhofar 1671 is recommended to further strengthen the link between OCs and RCs. [ABSTRACT FROM AUTHOR]

Copyright of Sultan Qaboos University Journal for Science is the property of Sultan Qaboos University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Moho and Moho Transition Zone (MTZ) of the Samail ophiolite of Sultanate of Oman are characteristic to potential occurrences of chromite deposit, hydrothermal mineralization and serpentinization. Mapping of Moho and MTZ, and discriminating them in between the mafic and ultramafic rocks in ophiolite sequence are more significant and important. The present study describes the remote sensing spectral characters of minerals and rocks of the Moho and MTZ and discriminates the Moho of Wadi Al Abyad of Nakhl massif, and Wadi Nidab and Wadi Abda regions of Sumail massif in the visible and near infrared (VNIR), and short wavelength infrared (SWIR) spectral regions using low-cost multispectral satellite data of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). Results of this study show that the red–green–blue (RGB) color composite images of ASTER spectral bands 8, 3 and 1, and 8, 7 and 4 are able to delineate the Moho and MTZ of the regions. The RGB images of ASTER band ratios (4/8, 4/1, 3/2 * 4/3 and (1 + 3)/2, (4 + 6)/5, (7 + 9)/8) are capable to discriminate the mantle material (ultramafic harzburgites) and crustal rocks (mafic gabbros). The occurrence of such rock types is demonstrated by detection of their minerals using Spectral Angle Mapper (SAM) image processing method. The presence of Moho and MTZ, and associated lithologies are verified in field at Wadi Al Abyad, Wadi Nidab, Wadi Abda, Wadi Tayin, Wadi Fizh and several locations of Nakhl regions of Samail ophiolites. The laboratory study shows the occurrence of typical minerals namely olivine, orthopyroxene and clinopyroxene in the harzburgite and the minerals such as plagioclase, clinopyroxene, hornblende, orthopyroxene and olivine in the layered gabbro. The spectral properties of the rocks are studied using Portable Infrared Mineral Analyzer (PIMA) spectrometer and the occurrences of minerals are confirmed by X-ray diffraction (XRD) analyses. This study demonstrates the sensor capability of ASTER to map Moho and MTZ, and thus it is recommended to the geoscientists and geophysicists working on Moho and MTZ. The satellite image interpretations of Moho and MTZ, and the associated rocks and minerals are consistent with the field research studies carried out in these regions. Our images have potential to map the chromites mineralized zone and dunites (refractory materials) bearing MTZ. [ABSTRACT FROM AUTHOR]

Copyright of Sultan Qaboos University Journal for Science is the property of Sultan Qaboos University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Economic important minerals and ore deposits are common in hydrothermal altered serpentinized zone. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite sensor is capable of discrimination of such hydrothermal mineralized zone and detection of hydrothermal altered minerals. In the present study, the hydrothermal altered serpentinized harzburgites of Wadi Hibi area of Northern Oman Mountains have been discriminated by using ASTER VNIR–SWIR spectral bands by image processing methods and the occurrences of Ni-magnesioferrite–magnetite–awaruite in the rocks are studied. The color composite RGB image developed using ASTER spectral bands 8, 4 and 1, mapped well the occurrence of weathered peridotites by pale green to dark blue in colors and discriminated the hydrothermally altered serpentinized rocks by pale brown to dark blue colors due to the strong absorption of OH and Mg–OH molecules that occurred in the serpentine minerals of the rocks in the study area. The ASTER band ratios 4/7, 4/1, and 2/3×4/3 RGB images studied are capable of discrimination of hydrothermal mineralized areas more clear by pale blue to purple colors due to the strong absorption of such hydroxyl bearing serpentine minerals. The studied image processing methods are evaluated by applying to the region of Wadi Sarami situated in the Semail ophiolite (Oman). In addition to that, the occurrence of serpentine minerals namely, lizardite and antigorite in the hydrothermally altered serpentinized region are detected qualitatively and quantitatively using Spectral Angle Mapper (SAM) supervised classification image processing method and studied. The interpreted images are verified in the field and checked for the occurrences of minerals including Ni-magnesioferrite, magnetite, pentlandite and awaruite and are confirmed through laboratory studies. Petrographic study of serpentinized harzburgites shows that the rocks consist predominantly of antigorite and lizardite serpentines, olivine and have the opaque minerals assemblage of Ni-magnesioferrite+magnetite+awaruite+pentlandite developed during serpentinization of the rock. The occurrences of such minerals are confirmed by XRD, electron microprobe analyses and spectral measurements in the laboratory. ASTER sensor proved its capability in discriminating the hydrothermal altered serpentinized zone and detecting the mineral occurrences and thus the study recommends the technique to the exploration geologists, scientists and mining geologists for mapping of such rocks and minerals in the similar arid region. [Copyright &y& Elsevier]

Abstract: Documentation of chemical weathering and CO2 sequestration in the Samail ophiolite massifs of the Sultanate of Oman represents an important case study for Geological Carbon Capture and Storage System (GCCSS). The present research study demonstrates the capability of remote sensing technique for mapping of weathered zones and potential CO2 sequestration area abundances at different scales within peridotites in the northern mountain region of the Samail ophiolite massifs. The carbonate mineral index (CI) applied with other mineral indices to the TIR wavelength region of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) TIR spectral bands 13 and 14 mapped CO2 sequestered minerals along the structural- and wadi-controlled CO2 flowing regions. Peridotites, the source rocks of CO2 sequestration in the study area, were mapped using an ASTER 8, 3 and 1 band combinations. The decorrelated Landsat TM image discriminated the rock types associated with peridotites of ophiolite sequences and delineated the region of weathered and altered serpentinized peridotites in the zone of CO2 sequestration. CO2 sequestration mapping was carried out using Landsat TM satellite data that span 20years (1986, 1998, 2000, 2003 and 2006) to assess the present status of CO2 sequestration in this region. The image interpretations are verified with existing geological maps and through field and laboratory studies. The spectral measurements of carbonate minerals at 1300 to 2500nm with the spectral resolution of ~7nm using a PIMA SP infrared spectrometer in the field and laboratory show the presence of hydroxyl-bearing minerals and carbonates that have spectral absorption features around 1.4μm, 1.9μm and 2.35μm. The strong absorptions around 2.35μm are mainly due to C O bonds in carbonate minerals such as calcite (CaCO3), dolomite (CaMg(CO3)2), magnesite (MgCO3), aragonite (CaCO3) and siderite (FeCO3), which form 15 to 57%, 12 to 53%, 9 to 38%, 11 to 21% and 3 to 8% respectively in the samples. The absorptions around 1.4μm and 1.9μm are caused by hydration effects of hydroxyl minerals including antigorite and montmorillonite present at 10 to 21% and 37 to 81% respectively in the samples. The alterations of serpentinite are evidenced by the presence of antigorite and lizardite minerals. X-ray powder diffraction analyses further confirms the occurrence of CO2 sequestered major carbonate minerals such as aragonite, calcite and dolomite in the samples. The study demonstrates that the ASTER and Landsat TM satellite multispectral sensors are useful to detect the carbonate minerals, to delineate the peridotites and to discriminate the areal abundance of potential CO2 sequestration. This technique is a useful tool to map and monitor the region of CO2 sequestration in well exposed arid and semi-arid regions and to analyze and understand this aspect of the world geological carbon capture and storage system. [Copyright &y& Elsevier]

Abstract: Listwaenites are highly altered ultramafic rocks that are potentially associated with economic mineralization and research on these is extremely important worldwide. In the present study, the classification of mineralized listwaenites developed along the serpentinite–amphibolite interface of the Semail Ophiolite, its associated lithology and the zones of alteration and mineralization in the Fanjah Saddle of the Central Oman Mountains region of the Sultanate of Oman are carried out, using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite data. The developed band ratioing, Principal Component Analysis (PCA) and the Spectral Angle Mapper (SAM) supervised classification and image processing techniques applied on the ASTER data set have proved their capability for better interpretation and identification of hydrothermally altered rocks and associated mineralization. The hyperspectral tools (Minimum Noise Fraction (MNF), Pixel Purity Index (PPI) and nD-visualizer) extracted end member spectra and SAM classification clearly show the occurrence of minerals and their spatial distributions. The promising results are verified and confirmed in the field by identification of alteration and mineralization such as listwaenites, silicification, serpentinization and talc alteration and are validated further through laboratory analysis. The confirmation of the occurrence of base metal mineralization along the serpentinite–amphibolite interface in listwaenites suggests that detailed investigation in this and other arid regions which have similar geological conditions may locate mineral deposits. The hyperspectral tools applied on ASTER satellite data show that these can be used as a powerful tool to explore the listwaenites and the potential associated mineralization in other arid geographical regions worldwide. [Copyright &y& Elsevier]

We developed a scientific proposal on spectral absorption in remote sensing and a new image-processing method that is purely based on multispectral satellite image spectra to map ultramafic lamprophyre and carbonatite occurrences. The proposed method provides a simple, yet efficient, tool that will help exploration geologists. In this proposal, in which the spectral absorption is applicable to all satellite images obtained in visible, reflected infrared, and thermal infrared spectral wavelength regions, we found that the carbonatites appear white in colour on a greyscale or RGB thermal infrared image obtained in the thermal infrared wavelength region (3–15 μm) due to molecular emission of thermal energy by such carbonate content, particularly the wavelength recorded by the sensor and that the variation of absorption in spectral bands of an outcrop is due to the differences in percentage of carbonate content or the spectral, spatial, radiometric, or temporal resolution of satellite data or the occurrences of carbonatites to incident energy. The results were confirmed by studying the spectral absorption characteristics of carbonatites in selected world occurrences including parts of Batain Nappe, Oman; Fuerteventura (Canary Islands), Spain; Mount Homa, Kenya; Ol Doinyo Lengai, Tanzania; Mount Weld region, (Laverton), Australia, and Phalaborwa region, South Africa, using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Landsat Thematic Mapper (TM) satellite data. A subsequent study of visible near-infrared (VNIR) and shortwave infrared (SWIR) ASTER spectral bands of Early Cretaceous alkaline ultramafic rocks of Batain Nappe, along the northeastern margin of Oman to map for the occurrences of carbonatite and aillikite (ultramafic lamprophyres) dikes and plugs, showed their detection mainly by the diagnostic CO3absorption (2.31–2.33 μm) in ASTER SWIR band 8. The results of image interpretations were verified and confirmed in the field and were validated through the study of laboratory analyses. A few more carbonatite dike occurrences were interpreted directly over the greyscale image of ASTER bands and true-colour interpretations of a Google Earth image along this margin. The carbonatites and aillikite occurrences of the area are rich in apatite, iron oxide, phlogopite, and REE-rich minerals and warrant new exploration projects. [ABSTRACT FROM PUBLISHER]

This workshop report describes plans for scientific drilling in the Samail ophiolite in Oman in the context of past, current, and future research. Long-standing plans to study formation and evolution of the Samail crust and upper mantle, involving igneous and metamorphic processes at an oceanic spreading center, have been augmented by recent interest in ongoing, low temperature processes. These include alteration and weathering, and the associated sub-surface biosphere supported by chemical potential energy due to disequilibrium between mantle peridotite and water near the surface. This interest is motivated in part by the possibility of geological carbon capture and storage via engineered, accelerated mineral carbonation in Oman. [ABSTRACT FROM AUTHOR]

Here we report an artiodactyl trackway from Musandam Peninsula, Sultanate of Oman. Epireliefs of the tracks are preserved in poorly consolidated aeolian deposits now making up the ceiling of a coastal cave. As an interesting morphological feature, the trackway documents the trackmaker negotiating a slippery dune slope at an angle. [ABSTRACT FROM PUBLISHER]

One of the major topics of debate in ophiolite geology is the original tectonic setting of ophiolites. New studies show that most ophiolites are formed more frequently in a supra‐subduction zone (SSZ) environment and that only a very small number of ophiolites have formed in an oceanic range (MOR). The Masirah ophiolite is one of the few oceanic ridge ophiolites that have been preserved, and the evidence that was formed in a subduction environment is missing (Moseley and Abbotts 1979, Dilek and Furnes, 2011; Rollinson, 2017). Masirah Island, the Batain and Ras Madrah areas of eastern Oman are almost entirely composed of a well‐developed ophiolite, known as the Masirah ophiolite (Fig. 1), which is, however, completely unrelated to the nearby Semail Ophiolite in the northern Oman Mountains (Fig. 2). The Masirah ophiolite is Jurassic in age and represents oceanic lithosphere derived from the Indian Ocean, but is about 15–20 Myr later than emplacement of mid‐Cretaceous Semail ophiolite in northern Oman. The presence of basaltic to rhyolitic lavas of calc‐alkaline affinity and boninites in the lava sequence of the Semail ophiolite led several researchers to propose a back‐arc basin model for this ophiolite (e.g. Tamura and Arai, 2006; Godard et al., 2008; Rollinson and Adetunji, 2015). The Masirah Ophiolite shows close affinities with MORB peridotites in general. Most of the olivine from the Masirah harzburgites show Fo contents that are similar to those of olivine from MORB. Both pyroxenes in these harzburgites have similar Mg# values, Al2O3 and Cr2O3 contents to those of pyroxenes from MORB peridotites. The observed primitive mantle‐normalized REE patterns showing enrichment in LREEs indicate that the Masirah peridotites have been modified by fluids or melts enriched in LREEs in a MORB environment. Podiform chromitites housed in ophiolites today interpreted as magmatic deposits formed during the reaction of molten rock in environments spike in the middle of the ocean (MOR) or suprasubduccion zone (SSZ) (Arai and Matsukage, 1998; Rollinson and Adetunji, 2015). The Masirah chromitites has a mineral chemistry similar to the mineral chemistry of chromite crystallized from MOR magmas. The Cr# values of chromite in the Masirah chromatite are similar to those of MOR peridotites. These findings suggest that the ultramafic and mafic cumulate rock assemblages overlying the upper mantle peridotites in the Masirah ophiolite represent the products of magma evolution in a MOR initiation stage within the proto Indian Ocean. Coexisting high‐ and low‐Cr# associations of chromitite and dunite have been found in the Semail ophiolite, which illustrates the common situation of ophiolites having both SSZ and MOR geochemical signatures. Cr# varies from 40–60 for shallow chromite bodies, and over the range 70–80 for the deep locations. This diversity of chromitite types suggests two stages of magmatic activity were responsible for the chromitite genesis, in response to a switch of tectonic setting. The first is residual from lower degree, partial melting of peridotite, which produced low‐Cr# chromitites at the Moho transition zone, possibly in a mid‐ocean‐ridge setting. The second chromitite‐forming event involves higher degree partial melting, which produced high‐Cr# discordant chromitite in the upper mantle, possibly in a supra‐subduction zone setting. Assemblages of mono‐ and poly‐phase silicate inclusions (including olivine, orthopyroxene, clinopyroxene, amphibole, phlogopite, serpentine, native Fe, FeO, alloy, sulfide, calcite, laurite, celestine and halite) within chromite have been observed in the low Cr# podiform chromitites from the Semail and Masirah ophiolites. The existence of hydrous silicate inclusions in the chromite calls for a role of hydration during chromite genesis. High‐T bright green hornblende–edenite included in the chromites is evidence of the introduction of water in the magma at the end of the chromite crystallization. Such paragenesis points to the presence of hydrous fluids during the activity of the shear bands. [ABSTRACT FROM AUTHOR]

Oil spill incidents contaminate water bodies, and damage the coastal and marine environment including coral reefs and mangroves, and therefore, monitoring the oil spills is highly important. This study discriminates the Wakashio oil spill, which occurred off Mauritius, located in the Indian Ocean on August 06, 2020 using the Sentinel-1 and 2 data acquired before, during and after the spill to understand the spreading of the spill and assess its impact on the coastal environment. The interpretation of VV polarization images of Synthetic-Aperture Radar (SAR) C-band (5.404 GHz) of Sentinel-1 acquired between July 5 and September 3, 2020 showed the occurrence and distribution of oil spill as dark warped patches. The images of band ratios (5 + 6)/7, (3 + 4)/2, (11 + 12)/8 and 3/2, (3 + 4)/2, (6 + 7)/5 of the Sentinel-2 data detected the oil spill. The images of decorrelated spectral bands 4, 3 and 2 distinguished the very thick, thick and thin oil spills in a different tone and showed clearly their distribution over the lagoon and offshore, and the accumulation of spilled oil on the coral reefs and along the coast. The distribution of post-oil spill along the coast was interpreted using the images acquired after 21 August 2020. The accuracy of oil spill mapping was assessed by classifying the SAR-C data and decorrelated images of the MultiSpectral Instrument (MSI) data using the Parallelepiped supervised algorithm and confusion matrix. The results showed that the overall accuracy is on an average 91.72 and 98.77%, and Kappa coefficient 0.84 and 0.96, respectively. The satellite-derived results were validated with field studies. The MSI results showed the occurrence and spread of oil spill having different thicknesses, and supported the results of SAR. This study demonstrated the capability of Sentinel sensors and the potential of image processing methods to detect, monitor and assess oil spill impact on environment. Image 1 • This study discriminates the oil spill of Wakashio, Mauritius using Sentinel data. • The study constructed band ratios to Sentinel-2 data to discriminate oil spill. • Decorrelation of Sentinel-2 bands showed the spread and thickness of oil spill. • Application of Sentinel-1 and 2 is assessed and validated with field studies. • This study demonstrates the sensor capability of Sentinel to map the oil spill. Sentinel-2 MSI optical spectral bands are capable of detecting thickness of oil spill monitoring marine oil spill and assessing their impacts. The outcomes support the results of Sentinel-1 SAR band. [ABSTRACT FROM AUTHOR]

Masirah Island is almost entirely composed of ophiolite, which is, however, completely unrelated to the nearby Semail Ophiolite of Oman. New studies show that ophiolites form most commonly in a subduction setting and that only few number ophiolites have formed at an ocean ridge. The Masirah ophiolite is one of the few true ocean ridge ophiolites that have been preserved (Moseley and Abbotts 1979; Dilek and Furnes, 2011; Rollinson, 2017) and lacks any indication that it formed in a subduction environment. The Masirah ophiolite is Jurassic in age and comprises two ophiolitic sheets and Mid Cretaceous ophiolitic mélange. The ophiolite is extremely well developed, and as well as the sheeted dykes, there are mantle serpentinites, several varieties of ultramafic to gabbroic cumulates, massive gabbros, pillow lavas, radiolarian chert, limestone and marl (Moseley and Abbotts 1979). The Masirah Ophiolite forms a straight NNESSW trending strip 40 km wide, extending 450 km from Ras Madrakah to the Batain coast. The Batain mélange is composed of several kilometres to a few metres blocks of all the rock types of the ophiolite. The predominant rock within the mélange is altered harzburgite, dunite pods, pyroxenite, with bastite pseudomorphs after orthopyroxene. Several chromitite deposits have been recently discovered in the ophiolite of the Batain mélange at Wadi Musawa, Eastern Oman. This is the first report of podiform chromitite from the Masirah ophiolite. These deposits have been extensively altered and deformed, with the host pyroxenite and dunite. The chromitites occur as separated small concordant, lenticular pods (3–10 m in thickness). The chromitites show mostly disseminated and massive textures. The spinel grains are reddish brown in thin section, and partly to completely altered to black chromite. Most primary silicate minerals are converted to secondary chlorite, serpentinite and pargasite. Olivine and clinopyroxene occurs as inclusions in the spinel grains. The forsterite content of olivine is between 90.0 and 92.0 in harzburgites and dunites. Discriminant geochemical diagrams based on the mineral chemistry of harzburgites indicate a Mid-Ocean-Ridge (MORB) origin. Orthopyroxene and clinopyroxene have moderate CaO, Al2O3 and TiO2 contents, resembling those of moderately depleted abyssal peridotites. Geochemical studies confirm that the Batain chromite is podiform type. Consequently, we propose that the Masirah ophiolite formed in a MORB setting. The chromitite deposits have similar cr# (0.54–0.59), mg# (0.6-0.64), Al2O3 and TiO2 contents to spinels found in MORB and has been interpreted as having formed in amid-ocean ridge setting. It appears that this chromite has been formed through reaction between a mid-ocean-ridge basalt- melt with depleted harzburgite in the uppermost mantle. ReferencesDilek, Y., Furness, H.,(2011): Ophiolite genesis and global tectonics: geochemical and tectonic fingerprinting of ancient oceanic lithosphere. Geological Society of America Bulletin 123, 387-411Rollinson, H. (2017): Masirah - the other Oman ophiolite: A better analogue for mid-ocean ridge processes? Geoscience Frontiers 8, 1253-1262.Moseley, F., Abbotts, I.L., (1979): The ophiolite melange of Masirah, Oman. Journal of the Geological Society of London 136, 713-724. [ABSTRACT FROM AUTHOR]

This study demonstrates the capability of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor data to remotely map industrial carbonate rocks known as the ‘Oman exotics’ of the Sultanate of Oman. We measured reflectance spectra of marble using a PIMA™ spectrometer and studied their spectral absorptions distinguishing calcite from spectral absorptions of dolomite of the same region. The spectral band 8 of ASTER is processed by simple decorrelation stretch image processing method to map the exotic limestone rock of the Nakhl region, Oman. Results showed that carbonate rocks displayed distinctive tonal variation on the image. A comparative study with the spectral band 7 of Landsat 7 (ETM+) does not discriminate the calcite-bearing marbles and associated carbonate formations in the studied area. ASTER data were also processed by the application of the Maximum Likelihood Classification (MLC), Spectral Angle Mapper (SAM) and Spectral Information Divergence (SID) image classification algorithms. The results were assessed by the production of a confusion matrix. The study shows the capability of visible near infrared (VNIR) and shortwave infrared (SWIR) spectral bands of the ASTER sensor and potential of the image processing methods to remotely identify industrial carbonate rocks and we recommend this technique to similar regions of the world. [ABSTRACT FROM AUTHOR]