Igneous Rock Fragments Research Articles

Mineralogy of Recent Sediments of Al-Teeb River Basin-East Missan Governorate, Southeastern Iraq

This research aims to define the mineralogical composition of recent sediments that were deposited around the Al-Teeb River basin in the east Missan Governorate and try to determine the provenance or the source of these sediments. The study area represents the southeastern edge of the Mesopotamian Plain and is part of it. 15 samples were collected from eight stations of recent sediment that was deposited around the Al-Teeb River; two field works are covered (December 2019 and August 2021). Mineralogical study of the sediment after separating the light and heavy minerals by heavy liquid Bromoform in order to determine the mineralogical composition of the studied samples by using the petrographic microscope the light mineral fraction composed (95.5%) of the total mineralogy. The light components of these sediments consist mainly of quartz about 25.31%, feldspars (potash and plagioclase feldspar) about 9.53%, sedimentary rock fragments (carbonate rock fragments up to 33.39%, chert rock fragments 7.65%, evaporates fragments, 7.31%), (igneous rock fragments, and metamorphic rock fragments about 6.94%). The major component of the heavy minerals residue is opaque minerals with a range of 36.76% and non-opaque minerals with a range of 63.24%. The non-opaque minerals are mainly of chlorite 7.42%, pyroxenes composed of both orthopyroxene and clinopyroxene 6.37%, amphiboles composed of hornblende, glaucophane, and tremolite 7.02%, (mica: biotite and muscovite) 9.81%, zircon 7.54%, tourmaline 5.1%, epidote group 5.91%, rutile 4.5%, kyanite 2.2%. The sediments have two types of stability: moderately stable and ultra-stable. The mineralogical composition shows that the major sources of these sediments are; the river terraces and flood plain of the river in the Mesopotamian Plain, another source of these sediments is the aeolian deposits that separated from sand dune fields in the studied area, and outcrops of ancient sedimentary formations in the southeastern of Iraq as specified by the incidence of the carbonate rock fragments.

Petrographic composition and material sources of Upper Paleozoic rough-clastic rocks in Western Taimyr

Research subject. Gravelites and conglomerates of the Upper Carboniferous and Permian of Western Taimyr. Aim. To reveal features of the petrographic composition of coarse clastic rocks and, on this basis, to clarify the ideas about the composition and position of the feeding province of the western part of the Taimyr sedimentary basin in the Late Paleozoic. Materials and methods. The analysis of materials collected during a layer-by-layer study of sections and microscopic description of 47 large transparent sections with the count of psephitic (more than 2 mm) fragments of quartzites, felsic and basic igneous, metamorphic and sedimentary rocks was performed. The revealed features of the petrographic composition of psephytoliths, in combination with a generalization of previously published geodynamic and paleogeographic reconstructions, were used to refine the model of the geological development of the Taimyr fold-thrust belt and adjacent areas in the Late Paleozoic. Results. It was established that the sections contain polymictic lithoclastic (83%) and petroclastic (15%) psephytoliths, with occasional inclusions of oligomictic essentially quartz varieties (2%). Minor changes in the composition of clasts over time indicate the existence of a single source of clastic material during the entire Late Paleozoic, which formed the sections of Western Taimyr. It was shown that the maturity of psephytolites increases from the southwest to the northwest and northeast. Numerous fragments of phtanites and lydites with remains of radiolarians of the Middle Devonian – early Early Carboniferous were identified, analogs of which are present in the Lemva zone of the Urals and in the basement of Western Siberia. Conclusions. The material forming the coarse clastic rocks of Western Taimyr was transported by the river for 600–1000 km from the folded structures of the “West Siberian land” located in the southwest (in modern coordinates), which formed in the Visean–Serpukhovian ages of the Early Carboniferous during the collision of the East - European, Kazakhstan and Siberian continental blocks.

Diamond-bearing fluidolites in the junction area of East European Platform and Urals fold region

Research subject. To characterize the Sylva fluidogenic-explosive complex, which was established in the junction area of the West Ural thrust megazone (head of the Sylva River) and the eastern wing of the Yuryuzano-Sylva depression of the Pre-Ural trough. Materials and methods. The authors' materials collected during research works at GSA200/2 sheet O-40-XXIX (Shalinskaya Ploshchad), as well as those collected during the work under the Priority 2030 Federal Program, were used. Data on the geology, petrochemistry, petrography, structural and tectonic position of clastogenic rock associations in the area of influence of the Main West Ural thrust were employed. Experimental data were obtained using a TESCAN VEGA LMS electron microscope equipped with an Xplore 30 energy dispersive X-ray spectroscopic prefix, and an URS-55 X-ray unit (Ural State Mining University), as well as CPM-35 and Shimadzu EDX-8000 spectrometers and an XRD-7000 diffractometer (Geoanalitik Centre, Zavaritsky Institute of Geology and Geochemistry of the Ural Branch of the Russian Academy of Sciences). Results. For the first time, the mineralogical-petrographic and chemical compositions of diamond-bearing rocks of the Sylva fluidogenic complex were established. Diamonds and minerals contained in the studied rocks were determined by XRD (sanidine, analcime, etc.). The conducted analysis of the rocks suggests their possible fluid-magmatic genesis, which is indicated by mineralogical features, including accessory minerals-indicators of diamond content, the presence of ellipsoid and teardrop-shaped volcanic glass, finely-dispersed bulk and poorly-rolled unsorted fragments of igneous and sedimentary rocks. Conclusions. The results obtained indicate the possibility of manifestation of Early Mesozoic phreatic volcanism in the studied area, which led to the transfer of the Sylva diamond complex and accessory minerals by fluidolites.

Provenance of sandstone layered in Injana Formation from Zawita and Dekala areas Northern of Iraq

To interpret the provenance 0f Injana Formation, 20 sandstone samples of Injana Formation were collected from Zawita and Dekala areas north Iraq (10 for each sections ), then thin section have been done sildes. The petrographic study showed that the sedimentary, metamorphic and igneous rock fragments, quartz (mono&polycrystalline) and feldspars (microcline, orthoclase and plagioclase) make up the main grain components of the sandstone. Carbonate cement is more common cementing minerals, and the matrix is subordinate. The percentage of mono-quartz and sedimentary, igneous rock fragments are greater than the amounts of feldspar and poly-quartzand metamorphic fragments. A diagenetic processes were represented by the carbonate, iron oxides and evaporite cements, as well as compaction, cementation, and dissolution. The majority of the rocks of Injana Formation’s provenances are sedimentary and igneous, with minor amounts of subordinate metamorphic rocks. These sandstones are considered to be immature and classified as immature Litharenites type. The tectonic provenances that are extrapolated from petrographical results are transitional and lithic with effect of uplifting of Alpaine oroging recycled origin which are derived from the order rocks during the Miocene age.

Kualitas Batuan Beku sebagai Bahan Konstruksi pada Daerah Warmare Kabupaten Manokwari

Warmare area, based on field appearances, found a lot of igneous rock fragments in the river found at the study site, especially andesite-basaltic rocks which are the constituent lithological units of the Arfak Volcano Formation found at the study site. These rocks are considered to be used as industrial raw materials, especially for basic infrastructure construction materials such as foundations, fills, road paving, dam supports, split concrete mixes and for other industrial base materials. This study aims to determine the quality of igneous rocks included in the Arfak Volcano Formation found in the research area and its surroundings based on the type of utilization. The method used is literature study, field data collection in the form of geological conditions in the research area and rock sampling, then laboratory analysis in the form of compressive strength tests, and petrographic analysis. The compressive strength test used is Uniaxial Compressive Strength, which aims to measure the uniaxial compressive strength of a rock sample in a regular geometry, either in the form of a cylinder, beam or prism in one direction (uniaxial). So that the test results can be classified as rock strength and characteristics. Based on field data taken in the form of Basalt showing a compressive strength value of 881.94 kg/cm2 which can be used as concrete piles referring to the Standard of the Directorate General of Highways (1976), Andesite rocks also found in the study area show a compressive strength value of 430.01 kg/cm2 which can be used as highway concrete.

Mineralogy of Recent Sediments of AL-Teeb River Basin East Missan Governorate Southeastern Iraq

The main aim of this research is to define the mineralogical composition of recent sediments deposited around the Al-Teeb river basin in eastern Missan, trying to determine the provenance or the source of these sediments. The study area represents the southeastern edge of the Mesopotamian Plain and is part of it. Quaternary deposits cover most of the area. It is clayey with old sea and river deposits and part of aeolian deposits. These sediments cover 95% of the study area, while the older rocks, which date back to the Tertiary (Late Miocene – Pliocene), exposed in the area east and northeast of the Al-Teeb area, made up hills which back to the undifferentiated Pliocene Mukdadiya and Bai-Hassan formations. The light components of these sediments consist mainly of quartz, feldspars (potash and plagioclase feldspar), sedimentary rock fragments (carbonate rock fragments, chert rock fragments, evaporates fragments), igneous rock fragments, and metamorphic rock fragments The heaviest minerals are opaque, amphiboles, pyroxenes, chlorite, epidotes, biotite, garnet, muscovite, zircon, kyanite, staurolite, and rutile. These sediments are typically formed by sedimentary rocks (single or many cycles), low and high-rank metamorphic rocks, acidic and basic igneous rocks, and pegmatite rocks. The high percentage of opaque heavy minerals in clastic sediment refers to unstable clastic sediments. The stability issue to the areas during the study shows that there are significant variances over the several places, indicating dissimilar sources and types of source rocks

Automated SEM Mineralogy and Archaeological Ceramics: Applications in Formative Period Pottery From the Atacama Desert

The analysis of archaeological ceramics has rapidly evolved over the last decades by the application of new analytical techniques. An emerging analytical proposal to fully characterise archaeological ceramics using automated SEM mineralogy is presented. A case study is provided of sets of ceramics from the San Pedro de Atacama oases in the Atacama Desert, northern Chile. Ceramic fragments of different typologies (i.e., Los Morros, Loa Café Alisado and San Pedro Negro Pulido) found in the Ghatchi archaeological sites are analysed. Our results include automated mineralogical maps, which are used to define the components that form the ceramic pastes, i.e., clay matrix and non-plastic inclusions, as well as grain size and mineral abundance information. We show that the pastes that define the studied ceramic types are more complex than previously suggested. The overall composition for these pastes corresponds to clay mineral-rich matrices containing non-plastic inclusions, such as mineral grains, crushed ceramic fragments, and sedimentary to igneous rock fragments, that may vary in composition, size, and abundance among the studied ceramic types. This mineralogical information allows us to discuss possible sources of raw materials by comparing these paste components with geological information. Here we interpret Los Morros and Loa Café Alisado as foreign ceramic types to Ghatchi, whereas the San Pedro Negro Pulido fragments found in this site agree well with the pottery paste recipe typically recognised in the San Pedro de Atacama oases. The petrographic-approach employed here supports the automated SEM mineralogy as a valid option for archaeometric studies of ceramic pastes since includes precise quantitative data formulated from the chemical composition of each component of the paste, which may provide valuable evidence into raw materials and technological styles.

Sedimentary and mineralogy characteristics of late quaternary sediments, Garmian area, Kurdistan Region, NE Iraq

The quaternary sediments have been studied in four sections; Garmian area, Kurdistan Region, North East Iraq, which are multi-features, multi-sources, and variable lithological compositional characteristics. The grain size granulometry was used and identified, gravel, sand and mud. Gravel-sized particles are partially producing a greater amount than sand and mud size in both sections (Sar-Qallah-1 and Salih-Agha). Statistical parameters such as (mean, mode, sorting, skewness and kurtosis), have shown that the sediments are very poorly sorted, very fine skewed and platykurtic. Petrographic studies of sediments under polarized microscope investigated that these sediments are predominately consisting of (chert and carbonate rock fragments), with the existence of few amounts of igneous and metamorphic rock fragments, feldspar and monocrystalline quartz. These fragments types are an indication of multiple source rocks originate from Ophiolites and thrust sheets from the Penjween area (North Iraq). Various types of heavy minerals are identified; opaque (hematite and pyrite), and nonopaque minerals (pyroxene, amphibole, epidote and zircon). X-ray diffraction technique is used to interpret clay mineralogy which indicates that chlorite and palygorskite are the main clay mineral with the presence of non-clay minerals such as quartz and calcite.

ИСТОЧНИКИ КЛАСТИЧЕСКОГО МАТЕРИАЛА И УСЛОВИЯ НАКОПЛЕНИЯ ОСАДОЧНЫХ ПОРОД ДАУРСКОЙ СЕРИИ АРГУНСКОГО КОНТИНЕНТАЛЬНОГО МАССИВА

The paper presents the results of geochemical and isotopic-geochemical (Sm-Nd) studies of the Upper Riphean (?) (in the Stratigraphic Scale of Russia) sedimentary rocks of the Urulungui and Dyrbylkey formations of the Daur Series in the Argun continental Massif, as well as U-Th-Pb and Lu–Hf isotopic studies of detrital zircons from these formations. Rocks of the Urulungui and Dyrbylkey formations differ significantly in mineral composition and content of the main elements, which is probably due to the degree of chemical weathering of the source rocks. Analysis of concentrations of trace elements in sedimentary rocks of the Urulungui and Dyrbylkey formations enabled to establish that they were formed in a subduction-related setting. The presence of conglomerate-breccias, conglomerates, gravelstones, fragments of igneous and volcanic rocks, a weak degree of roundness of clastic material, as well as abundant Neoproterozoic detrital zircons in the formations is evidence of tectonic and igneous activities in the region during sedimentation. Sedimentary rocks of the Urulungui Formation are characterized by two-stage model ages TNd(DM2) = 2.0–2.1 Ga, and the Dyrbylkei Formation – TNd(DM2) = 1.6–1.8 Ga according to the results of Sm-Nd isotopic-geochemical studies. The abundant Neoproterozoic zircons in sandstones of the Urulungui and Dyrbylkey formations suggest that Neoproterozoic igneous rocks widely developed within the western Argun continental Massif were the main source of clastic materials. At the same time, the presence of Early Precambrian detrital zircons is evidence that Early Precambrian rocks were also present in the source area. However, Early Precambrian igneous and metamorphic associations whose age would be reliably determined from geochronological data have not yet been found so far within the Argun continental Massif, and thus it is not out of the question that rocks of the Daur Series form a «detached block» intruded in the Argun Massif.

Geochemical insights into formation of enigmatic ironstones from Rio Grande rise, South Atlantic Ocean

Rio Grande Rise (RGR) is an intraplate oceanic elevation in the South Atlantic Ocean that formed at a hotspot on the Mid-Atlantic Ridge during the Cretaceous. In spreading center and hotspot environments, ironstones form mainly by biomineralization of reduced Fe from hydrothermal fluids or oxidation of sulfide deposits. However, RGR has been considered aseismic and volcanically inactive for the past 46 Ma. Here, we investigate the origin of ironstones collected from the summit of RGR using multiple techniques: petrographic observations, X-ray diffraction, U-Th/He geochronology, and chemical composition. The ironstones from RGR consist of finely laminated goethite containing igneous rock fragments, carbonate fluorapatite, and calcite. Our results suggest that Fe oxyhydroxides were precipitated by Fe-oxidizing bacteria forming bacterial mats. The bacterial Fe mats underwent compaction, dewatering, goethite crystallization, and cementation that created the ironstone deposits. U-Th/He geochronology reveals protracted goethite minimum ages extending from the late Miocene to the Quaternary, probably due to multiple generations of mats, slow mineralization rates, and Fe-oxide dissolution-reprecipitation cycles. Flame-like goethite structures underneath FeMn crusts and a chimney-shaped goethite sample with a central channel indicate that the dewatering fluid flowed upward through the deposits, or a thermal fluid source may have been introduced from below the ironstone deposits. High Fe/Mn ratios, low trace metals contents (Ni + Co + Cu), and very low Fe/REY ratios suggest ironstone precipitation from a hydrothermal fluid; however, REYSN plots and bivariate CeSN /CeSN⁎ versus YSN/HoSN and CeSN /CeSN⁎ versus Nd plots are inconclusive, and a proximal source of magma was unlikely during the period of mat formation. Given this evidence, we hypothesize that a geothermal circulation system may have facilitated ironstone mineralization at RGR.

Sedimentological Properties of the Sand Dunes and Valley Sediments in Al-Muthanna, Southern Iraq

Sedimentological properties of the dunes and valley terrigenous sediments in Al-Muthanna Governorate, southern Iraq were carried out. Ten samples were collected, where five samples from both sand dunes, and valley sediments. Grain size analysis revealed that sand, silt and clay fractions are the constituents of these sediments. Sand fractions predominant in the dunes and the texture is classified as silty sand, whereas clay fractions dominate in the valley sediments, with sandy clay texture. The mineralogy is determined by X-ray diffraction, which revealed that quartz is the main mineral in both study areas, followed by calcite, feldspars in lesser amount and evaporates (gypsum) in minor component of the light minerals. Petrographically, monocrystalline quartz dominates over polycrystalline quartz in both areas. Rock fragments in the valley sediments are higher than in the sand dunes, which are comprised of carbonate, chert, igneous, metamorphic, evaporate, and mudstone rock fragments. Feldspars are approximately similar in the study areas and comprised mainly alkali feldspar (potash feldspar) and plagioclase. Petrogenically, the sand dunes occupy the quartzose-recycled field, while the valley sediments fall in transitional recycled fields represented recycled orogeny.

ГЕОХИМИЧЕСКИЕ ОСОБЕННОСТИ И ПАЛЕОГЕОДИНАМИЧЕСКИЕ ОБСТАНОВКИ НАКОПЛЕНИЯ ПЕРМСКИХ И ТРИАСОВЫХ ОТЛОЖЕНИЙ ЮГА ЛАОЕЛИН-ГРОДЕКОВСКОГО ТЕРРЕЙНА (ПРИМОРЬЕ)

New geochemical data on the Late Paleozoic and Early Mesozoic sandy rocks of the southern part of the Laoeling-Grodekovo terrane of the South-Western Primorye are presented. It is shown that terrane deposits differ significantly in geochemical parameters: sandstones of the Barabash and Mangugai formations most closely correspond to the graywackes, those of the Kazachka formation to the lithite arenites, and those of the Reshetnikovka formation to arkoses. The rocks are characterized by a rather high degree of maturity of the terrigenous material and contain mainly fragments of acidic igneous rocks in the clastic part. The geochemical data obtained were generalized and interpreted based on their comparison with the compositions of modern sediments and ancient deposits accumulated in the known geodynamic settings. The results of the studies, in general, suggest the formation of terrane deposits in a basin associated with the setting of transform slip of lithospheric plates. The main source of detrital material was eroded acid igneous rocks, to which a small fraction of products of disintegration of basic-middle volcanics and sedimentary rocks enriched in ancient components was added.

Palaeoweathering, Tectonic Setting and Climatic Condition of Sabarmati Alluvial Plain in Ahmadabad City, Gujarat, Western India

The present study emphasizes major elemental geochemical attributes-based prediction of nature, palaeoweathering intensity, provenance, tectonic setting and palaeoclimatic condition of source area of Sabarmati alluvial sediments lying in Ahmadabad locality, Gujarat, India. The sediments successions are comprised of gravel, poorly graded sand, with dominant silty and clayey sands, silt and clay with low-to-high level of plasticity. The sediments exhibit increasing concentration of MnO followed by P2O5, TiO2, K2O, MgO, Na2O, CaO, Fe2O3, Al2O3 and SiO2 which supports quartz dominating sand layers in comparison with silty and clayey sequences. The values of SiO2/Al2O3, Na2O/Al2O3 and K2O/Al2O3 and higher values of ICV indicate immature sediments with low dilution of ‘Na’ and ‘K’. Lithologically, the majority of sediments belong to shale and Fe-shale varieties. The values of ICV, CIA, CIW and PIA and various bivarient and discrimination diagrams reveal the mechanical fragmentation, abrasion and low to moderate degree of chemical palaeoweathering of fragments of felsic and intermediate igneous rocks of rift basin located at island arch and active continental margin under arid/semi-arid conditions sporadically interfered by short-term humid and semi-humid climatic conditions were responsible for formation of sediments sequences of the area.

Age and provenance of upland gravels in Missouri, USA, and their relationship to Early Pleistocene glaciation

The age and origin of the Grover Gravel, which is preserved on stable uplands in St. Louis County, Missouri, USA, and similar gravels along the Mississippi River bluffs farther south, have been controversial for over a century. These gravels have some features consistent with a glacial origin but lack obvious erratics such as igneous rock fragments. New observations, however, show that the earliest tills within the Mississippi basin nearly lack such constituents as well, and that the Grover Gravel is a Pleistocene deposit derived from such a till. A Mississippi River terrace deposit in St. Louis County also includes typical clasts of this till and formed between 2.0–1.8 Ma, based on various dating methods. This deposit may correspond to a pulse of glacial meltwater recorded within sediment near the mouth of the Mississippi River and represent outwash from a previously unrecognized glaciation within the US midcontinent. The Mounds Gravel (or Upland Complex) is present farther south around the perimeter of the Mississippi Embayment and contains the same distinct clasts as the gravels in St. Louis County. Given that the age of the Mounds is <~3 Ma based on cosmogenic‐nuclide ratios, the southern gravel could be the same age as the gravel terrace in St. Louis County. If so, these gravels could mark a geomorphic transition to glacial‐dominated sedimentation farther south in and around the Gulf of Mexico. Regardless, all the upland gravels have insignificant amounts of zircon from provinces west of Hudson Bay. Therefore, detrital zircon provenance does not support a recent hypothesis that the Mounds (Upland Complex) was deposited by a giant Mississippi River with a drainage basin extending across broad areas west of Hudson Bay.

Petrography, modal composition and tectonic provenance of some selected sandstones from the Molteno, Elliot and Clarens Formations, Karoo Supergroup, in the Eastern Cape Province, South Africa

Abstract The Late Triassic - Early Jurassic non marine clastic sediments of the Molteno, Elliot and Clarens Formations were studied to deduce their mineralogy and tectonic provenance. The study is based on road-cut exposures of the formations in the Eastern Cape Province of South Africa. Petrographic studies based on quantitative analysis of the detrital minerals shows that the clastic sediments (mostly sandstones) are predominantly made up of quartz, feldspars, and metamorphic and igneous rock fragments. Among the main detrital framework grains, quartz constitutes about 62-91%, feldspar 6-24% and 3-19% of lithic fragments. The sandstones can be classified as both sublitharenite and subarkose. Although, most of the sandstones (> 70 %) plotted in the sub-litharenite field. Petrographic and XRD analyses revealed that the sandstones originated from granitic and metamorphic rock sources. The QFL (Quartz-feldspar-lithic fragments) ternary diagrams indicate that the sandstones were derived from recycled or quartzose source rocks reflecting a craton interior or transitional continental setting which probably came from the Cape Fold Belt. This possibly revealed that most of the sandstones might have been derived as a result of weathering and erosion of igneous and metamorphic rocks in the Cape Supergroup. The study has revealed the depositional environments, and provide a basis for the description and interpretation of the sedimentology of the Molteno, Elliot and Clarens Formations.

The Effect of Deep Burial and Folding on Sandstone Reservoirs in some Giant Gas Fields, South America

The underthrust fold belt of the Andes contains some very large gas fields in which the Lower Palaeozoic Sandstone reservoirs are buried to depths of over 4-6km. The foreland depositional environment received high amounts of metamorphic and igneous rock fragments and deep burial was accompanied by substantial tectonic folding and fracturing. The combined effects of Temperature, Pressure and time on these labile sediments have reduced typical porosities <7% and matrix permeabilities <1mD so that these reservoirs are ultra-tight and effectively unconventional. Nevertheless, the fields contain very large recoverable amounts of gas with minor liquids per well. They provide an intriguing case study that contrasts with the typical concept of a conventional petroleum sandstone prospect and pose the question how many more large gas fields fit this model? These complex structural fields required modelling by 3D-Geo using fractured and folded simulation models. The micro-porosity and micro-permeability has been investigated by Curtin University using nano-scale special core analysis in an attempt to identify where the hydrocarbons reside in these rocks, how they migrate out on production, and how best to estimate and optimize ultimate recovery? High technology characterization included TIMA-SEM to map mineralogy and texture at the nano-scale; X-ray Micro-CT analysis of 3D microstructure; NMR, ultra-low Helium porosity and permeability, Hg injection for capillary pressure; Elastic and Electrical Properties to tie the seismic and log data for the modelling. Tri-axial tests helped understand the structural and tectonic history and its relation to the burial history of the reservoirs.

Comparison of Provenance of the Injana and Mukdadiya Formations in Zorbatiya area, Wasit Governorate, East of Iraq

Petrographic, heavy mineral and clay mineral analyses are carried out for the sandstone and the mudstone units of Injana and Mukdadiya Formations in Zorbatiya area, Wasit Governorate, East of Iraq. The sandstones and the mudstones are nested as repeated fining�upwards successions, representing fluvial deposits. The sandstones of the Mukdadiya Formation is gravelly and on occasions becomes conglomerate. The sandstone of both formations comprises rock fragments, quartz and feldspars. The rock fragments are the dominant component consisting sedimentary, igneous and metamorphic rock fragments, accordingly these sandstone are classified as litharenite. The clay minerals of the mudstone units are mostly illite, kaolinite, chlorite and mixed-layered clay. The mineralogic and petrographic data suggest the derivation of Injana and Mukdadiya Formations from nearby sources with contribution from igneous, metamorphic and sedimentary provenance and deposited in arid climate. The Mukdadiya deposits are rich with Paleogene deposits, some of which are coarse and cobbly.

Characterization of strain-burst rock fragments under a scanning electron microscope – An illustrative study

Fractures around excavations in hard, fine-grained, brittle rock sometimes display unique patterns from which an interpretation of the manner of failure/fracture propagation can be made. Igneous rock fragments from a strain-burst event at a site in Western Australia have been studied under a Scanning Electron Microscope (SEM) in order to characterize their surficial features. SEM image analysis indicates that anisotropy, a contrast in geomechanical properties, geometry and contact patterns present at the micro-scale as they do at the large mine/drive scale. It is proposed that these micro-scale features can lead to anisotropic material behaviour and stress concentrations that manifest as strain-burst events.

Mineralogy of Duné s Sand of Missan Dune Fields Southeastern Iraq

The aim of this study is to define the mineralogical composition of Missan dune fields South Eastern of Iraq, and try to determine the origin or the source of these dunes .&#x0D; Three main types of dunes were recognized in the studied area, these are: barchanoid ridge, barchans and nabkha dunes. The direction of these dunes is northwest to southeast.&#x0D; The dunes in Missan dune fields were divided into three fields according to the vari- eties in the composition and geographical position in the studied area, these three fields are: Al-Manziliyah, Middle Chailat, and Said Subair dune fields.&#x0D; 9 samples were collected from these fields, the samples were separated into light and heavy fraction by heavy liquids. The light fraction composed from quartz, feldspar, and rock fragments, the rock fragments composed mainly of carbonate, chert, igneous, and metamorphic rock fragments .&#x0D; The heavy minerals are mostly opaques, chlorite, pyroxenes, amphiboles, epidotes, zircon, garnet, muscovite, biotite, kyanite, staurolite, and rutile .&#x0D; The percentages of heavy minerals fraction to light minerals fraction was very vari- able in which the percentage of heavy minerals in Sayid Subair field are higher than the percentage in Al-Manziliyah field.The source area of these sediments is the recent sed- iment that deposited in the flood plain and traces of the Tigris river and the outcrops of upper Miocene-Pliocene rocks in the eastern of studied area (Himreen Anticline and Zagros Mountain).

Sandstone memory of a Late Paleozoic continental arc in southeast China (Lower Yangtze region)

Provenance analysis was carried out on Paleozoic siliciclastic rocks exposed in the South China Block (Lower Yangtze region, Chaohu and Nanjing areas) by sandstone petrography, U-Pb detrital-zircon geochronology, and zircon Hf isotopes. Sandstones of the Silurian Fentou Formation are feldspatho-quartzose with a few igneous and low-grade metamorphic rock fragments. Sandstones of the Devonian Wutong Formation are quartzose with a few quartz-rich metamorphic rock fragments. The Fentou and Wutong formations share similar detrital-zircon age spectra, with peaks mainly at 465−420 and 838−812 Ma. Zircons of Early Paleozoic age were with all likelihood derived from magmatic rocks associated with the Kwangsian orogeny, documented by a widespread unconformity across the South China Block. Neoproterozoic zircons were probably shed from Proterozoic basement of the Wuyi terrane in the Cathaysian block, interpreted to have been uplifted south of the Lower Yangtze region during the Kwangsian orogeny. The Permian Longtan Formation in Chaohu area and Nanjing area are litho-quartzose and feldspatho-quartzose, respectively, with dominant felsic and intermediate volcanic lithic fragments, indicating that detrital source areas did not change markedly after the Kwangsian orogeny. Zircon-age spectra from the Longtan Formation in the Chaohu area display a diagnostic peak at ~ 1866 Ma, indicating provenance from the Paleoproterozoic basement of the Wuyi terrane. Instead, detrital zircons in the Longtan Formation in the Nanjing area display peaks at ~ 445 and ~ 970 Ma, similar to those in the underlying Paleozoic sandstones. The Wuyi terrane in the Cathaysian block thus remained as a major source area for long, as supported by independent sedimentological and seismic evidence. The Longtan Formation in both Chaohu and Nanjing areas also contain detrital zircons with ages distributed continuously from 341 to 254 Ma and a major peak around 270 Ma, reflecting renewed intermediate and felsic magmatism in the source area. These zircons have e Hf( t ) ranging from −19.8 to +14.9, indicating melting of old crust and mixing with crustal magmas. Such a continuously magmatic source supplied sediments all across the South China Block from east to west. These and other lines of evidence including probability accumulation-curve analysis favor deposition in a convergent plate-tectonic setting. We suggest that source rocks were part of a continental arc developed along the southeast coast of China during the Late Paleozoic, shedding sediments to as far as north as the northern South China Block. According to previous studies, such continental arc would be related to the subduction of the paleo-Pacific plate. Magmatism generated at first by melting of old crust was mixed later on with felsic and intermediate magma newly generated during mantle upwelling and associated uplift. The continental arc remained as the main detrital source to the Lower Yangtze region and other parts of the South China Block until it was eventually denudated or buried by the Mesozoic times.