Quartz-mica Schist Research Articles

Geophysical characterization of the bedrock and regolith in the Pranmati basin critical zone, Uttarakhand Himalaya

The young active Himalayan mountain is characterized by steep slope and dissected topography in overall compressive tectonic setting. The mountain belt has primarily coarse textured soil with poor water holding capacity and is highly prone to erosion. The erosion not only affects many ecosystems located at downstream but also has detrimental effects on the critical zone (CZ). In the present study, we have carried out DC electrical resistivity study in the Pranmati catchment of the Alaknanda basin, a Himalayan critical zone in the Lesser Himalaya, to understand the pattern of soil erosion, transportation and deposition by characterizing the bedrock architecture and hence regolith thickness. A total of 6 electrical resistivity tomogram (ERT) profiles were laid at two locations in the catchment, one in a plain grassland and another at a crop field located on a hill slope of >25o. The study area in the Baijnath klippe, consists of quartz-biotite gneisses with layers of quartz mica-schist enclosed by thrust faults. Electrical resistivity sections of the downslope grassland site show a sharp resistivity contrast between the southwest and northeast transects suggesting south-eastern increase in dip of the bedrock, oblique to the north-east facing surface topography and a thick regolith (> 10 m). The resistivity sections of the site located on the hillslope yield a very thin layer of regolith (< 2 m) indicating significant soil erosion and high weathering of the bedrock. We propose that the water–rock interaction within the porous regolith facilitated by subsurface water circulation might be a potential source for the thick regolith. The observations substantiate existing hypotheses for the evolution and development of deep critical zones. From the results, it has been hypothesized that the bedrock architecture and water channel paths within the CZ together control the regolith thickness.

Detrital zircon U-Pb-Hf isotopes of late Meso-Neoproterozoic metasedimentary rocks in the South Altyn Tagh: Implications for tectonic affinity of microcontinents in NW China

The Neoproterozoic tectonic correlation between the Central-South Altyn, Qilian, Qaidam, and East Kunlun blocks in northwestern China remains controversial, with competing models favoring separate blocks or a unified single block, and debatable paleo-positions in the Rodinia supercontinent. In this study, we present a systematic provenance study on the late Mesoproterozoic to Neoproterozoic metasedimentary rocks from the South Altyn Tagh. A mica quartz schist sample from the Bashikuergan group yielded a maximum depositional age of 1050 ± 31 Ma. Four paragneiss samples from the Altyn Complex yielded maximum depositional ages of 1106 Ma, 1065 Ma, 1054 Ma, and 870 Ma. Given that the Altyn Complex was intruded by numerous early Neoproterozoic granitoids (ca. 976–900 Ma), we propose that the sedimentary protoliths of the Altyn Complex and the Bashikuergan Group were deposited at two stages, i.e., ca. 1105–975 Ma and after 870 Ma. Provenance tracing indicates that these 1105–975 Ma sediments probably received detritus from the late Mesoproterozoic rocks of Western Australia, East Antarctica, and Central Indian Tectonic Zone in India. In contrast, the detritus of the paragneiss (deposited after 870 Ma) was likely sourced from local regions in the Altyn Tagh orogen. Combined with the comparable magmatic, sedimentary, and tectonic records, we propose that a few microcontinental fragments in northwestern China, including Central-South Altyn Tagh, Qilian, Qaidam, and East Kunlun blocks, constituted a unified block in the early Neoproterozoic and occupied a periphery position of the Rodinia supercontinent with a close paleogeographic affinity to South China and Northwest India.

The Mount Distin assemblage: Neoproterozoic metasedimentary rocks in the Nome Complex of Seward Peninsula, Alaska, USA

Proterozoic to Paleozoic rocks involved in Jurassic and earliest Cretaceous (Brookian) orogenesis and subsequently extended, metamorphosed at high temperature and intruded by Cretaceous plutons, are widespread on the Seward Peninsula, Alaska, USA. These blueschist and greenschist facies metasedimentary and metaigneous rocks make up the highly deformed Nome Complex. We describe and bracket the age of a distinct Precambrian succession in the Nome Complex, the Mount Distin assemblage (informal). The Mount Distin assemblage consists of marble, impure marble, calc-schist, quartz mica schist, and lesser quartzite that was originally a shelfal succession. Metamafic bodies, originally dikes and/or sills, are minor but common components. Three new U-Pb detrital zircon (DZ) samples are characterized by numerous peaks between 1.5 Ga and 1.0 Ga, with minor ages of 1000−900 Ma and 2000−1500 Ma and only 1−2 grains 3.0−2.5 Ga, indicating maximum depositional ages of 1000−900 Ma. A new U-Pb zircon age for an orthogneiss lens in marble is 661 ± 3 Ma like others previously dated in the Nome Complex. Orthogneiss ages provide an upper age limit for the Mount Distin assemblage of ca. 687 Ma, the oldest reported date. Zircons in three other orthogneiss bodies are interpreted as inherited as they have a range of U-Pb ages like those in their country rocks. The Mount Distin assemblage DZ ages are like those from schist-bearing carbonate sequences in the Central and Schist belts of the Brooks Range and inherited zircon populations in Neoproterozoic plutons on Wrangel Island, Russia. The discovery and documentation of the Mount Distin assemblage explains the previously reported enigmatic lack of country rocks to Neoproterozoic orthogneiss bodies, establishes the continuity of older rocks across the entire extent of the Arctic Alaska−Chukotka microplate, and further confirms this microplate’s Baltica affinities.

2.13 Ga Lawsonite/Barroisite-Bearing E-Morb Signature Metagabbro Associated with Spinel Metaperidotite from Itaguara (São Francisco Craton, Brazil): Oldest Blueschist-Facies Fragment of Oceanic Moho?

In close association with Paleoproterozoic retroeclogite and accretionary prism-related mica-quartz schist, a 2.13 Ga (metamorphic titanite U-Pb age) lawsonite/barroisite-bearing E-MORB signature metagabbro associated with spinel metaperidotite is found in the Itaguara Sequence from southern São Francisco craton, Brazil. Petrography and pressure-temperature equilibrium phase diagrams suggest that the metagabbro experienced blueschist-facies metamorphism, attaining peak metamorphic conditions at ~16 kbar and ~450 °C during subduction. The retrograde metamorphic path crossed epidote amphibolite-facies, in which the mineral assemblage found in metaperidotite (olivine, clinopyroxene, spinel, serpentine, chlorite, talc, and tremolite) was stable during a ca. 2.1 Ga continental collision-related exhumation that occurred between the Archean Campo Belo/Bonfim and Divinópolis complexes. This geological framework suggests that the metagabbro and adjacent spinel metaperidotite represent a subducted and exhumed blueschist-facies fragment of a Paleoproterozoic oceanic Mohorovičić (Moho) discontinuity, thus establishing the Itaguara metagabbro as the oldest-known occurrence of retrogressed blueschist and providing evidence for the activity of the modern-style plate tectonics more than 2 Gyr ago.

Sulfide Remobilization in the Metamorphosed Kayad Sedimentary Exhalative Zn-Pb Deposit, Western India: Evidence from Mode of Occurrence, Texture, Hydrothermal Alteration Features, and Trace Element Chemistry

Abstract The Kayad Zn-Pb deposit, situated within the Proterozoic Aravalli-Delhi fold belt in western India, is primarily characterized by sphalerite and galena along with pyrrhotite and chalcopyrite. The mineralization occurs as disseminated ores in quartzite, disseminated/laminated and massive ores in quartz-mica schist, and in pegmatite and quartz veins. The laminated ores conform to the regional schistosity and folding, whereas the massive Zn-Pb ores postdate the pervasive tectonic fabric, accumulating at the fold hinges. The massive ore is characterized by durchbewegung texture, discrete blebs of galena and chalcopyrite in a sphalerite matrix with low interfacial angles, and discrete intergrowths of sulfides and sulfosalts such as pyrargyrite, gudmundite, Ag-tetrahedrite, and breithauptite. Geochemical analyses of sulfides reveal microinclusions of sulfosalts comprising Ag, Sb, Cu, Tl, and As, which are regarded as low-melting chalcophile elements (LMCEs). Hydrothermal alteration is insignificant in the laminated and massive ores but prominent around Fe-Cu ± Zn-Pb and Zn-Pb ± Fe-Cu veins. The alteration assemblages in these veins evince a pervasive K + Na ± Fe alteration, later overprinted by a subsidiary Ca ± Na alteration. We interpret the laminated/disseminated ores to be of syndiagenetic sedimentary-exhalative (SedEx) origin formed within an euxinic basin. Conversely, the textural features, mineralogical composition, lack of associated hydrothermal alterations, and evident structural influence on the emplacement of the massive ores suggest they have been remobilized both via plastic flow and by sulfide partial melting. Temperature estimates of up to 650°C, derived from Ti-in-biotite geothermometry of the metamorphosed host rocks, indicate lower-middle amphibolite facies conditions during regional metamorphism. The initiation of melting at these temperatures was promoted by the desulfurization of pyrite to pyrrhotite in quartz-mica schist, aided by melting point depression due to the presence of LMCEs like Ag, Sb, and As.

Provenance of the lower Cretaceous Lumshiwal Formation, Surghar Range, northwestern Indian Plate, Pakistan: Insights from new petrographical and geochemical analysis

This paper documents the provenance and palaeoclimatic conditions of the Cretaceous Lumshiwal Formation near the western margin of the Indian plate in the Surghar Range, northwest Pakistan. The combined techniques of petrography, X-ray diffraction (XRD), and bulk rock geochemistry were utilized to reveal the source and mineral-geochemical composition and sandstone type. The petrographic analysis of the sandstones confirms the dominance of quartz, feldspar, and rock fragments, with subordinate occurrences of muscovite, magnetite, and hematite. Heavy minerals consist of tourmaline, titanite (sphene), rutile, cassiterite, monazite, and zircon. The cementing material includes ferruginous clays, jarosite, glauconite, calcite, minor dolomite, gypsum, and silica. The modal composition plot of the sandstones falls into arkose to sub-arkose, with a few lithic arkose varieties. Lithic fragments mainly include granite, with a minor occurrence of granitic gneiss, chert, phyllite, and quartz mica schist. The discriminatory provenance diagram of the sandstones suggests a transitional continental provenance. The bulk rock geochemistry of the sandstones reveals the presence of SiO2, TiO2, Al2O3, Fe2O3, FeO, MnO, CaO, MgO, Na2O, K2O and P2O5. The petrographical mineral findings were corroborated with XRD, SEM, and bulk rock geochemistry analysis (major element concentrations and their ratios), which collectively all confirm a felsic igneous source. The tectonic discrimination diagram (SiO2-log K2O/Na2O wt %) implies a dominant influx of sediment sourced from the passive continental margin of the uplifted Gondwana Indian plate. Terrigenous sediments found in the Lumshiwal Formation are interpreted to have been derived from granites and granitic gneisses of the Indian Shield. The palaeo-weathering index, including the chemical index of alteration (CIA) and the chemical index of weathering (CIW) of the Lumshiwal Formation confirms a low to moderately weathered source area. The climate discrimination plot (SiO2 versus Al2O3 + Na2O + K2O) shows that humid to semi-humid climatic conditions during the deposition of the Lumshiwal Formation.

The Kuching Formation: A deep marine equivalent of the Sadong Formation, and its implications for the Early Mesozoic tectonic evolution of western and southern Borneo

The pre-Cretaceous history of Borneo remains relatively poorly studied. Limited exposures of Palaeozoic and lower Mesozoic rocks are located in NW Kalimantan and in West Sarawak, an area interpreted as the West Borneo basement. Lower Mesozoic sedimentary rocks in West Sarawak were analysed to study their depositional environments and implications for the tectonic evolution. Upper Triassic turbidites in West Sarawak, exposed in the northern part of Kuching city, informally named the Kuching Formation, are the deep marine equivalent to the more widespread, shallow marine Sadong Formation. The Kuching Formation comprises thinly-bedded stacked turbidites, consisting of incomplete Bouma sequences, with multiple, erosive channel sandstone bodies deposited under upper flow regime waning flows. Thin debrites with abundant coaly-material are interbedded with the channel sandstones. The Kuching and Sadong formations both contain volcaniclastic detritus that was derived from the westward-subducting Palaeo-Pacific plate, forming a Triassic Andean-type arc which extended from West Borneo in the south to southern China, Taiwan and Japan in the north. Palaeoproterozoic to Archean detrital zircons in the Kuching and Sadong formations reveal a Cathaysian basement source, providing insights into the nature of the West Borneo basement. Quartz-mica schists (Kerait Schist, Tuang Formation) in fault-contact with the two sedimentary successions may have formed during accretion.

A Study on the Geological Characteristics and Genetic Types of Dashipo Andalusite Deposit in Yingjiang County, Yunnan Province

The Dashipo andalusite deposit in Yingjiang County, Yunnan Province is taken as an example in this article to discuss the geological characteristics of andalusite ore occurrence and to analyze the genesis of the deposit. The ore body is mainly found in the middle strata of the Upper segment of the Gaoligongshan Group in the Middle Proterozoic (Pt2gl2), with the ore-bearing layers consisting of Andalusite mica schist, Andalusite mica quartz schist, and Andalusite mica quartz schist. The main features of the deposit include its super-large scale, the medium to stable distribution of the ore layer, and the uniform grade changes. Most of the red feldspar in the deposit is composed of self-shaped to semi-self-shaped long columnar metamorphic crystals that are distributed along the schistosity of the ore layer. The ore material has a simple composition with relatively low content of harmful components, making it rare in China. Based on the location of the deposit, characteristics of the ore body, structural features of the ore, mineral associations, and chemical composition of the ore, it is preliminarily believed that the deposit belongs to the regional metamorphic type, which holds great significance for searching for similar types of deposits.

Hydrogeochemical Assessment of Groundwater Quality and Geological Influence in Igarra and environs, Southwestern Nigeria

The impact of Geology on groundwater is not fully appreciated in many Nigerian groundwater quality literature. This study investigates the influence of Geology on the hydrogeochemical makeup of groundwater in Igarra and environs, Nigeria. Igarra and environs is underlain by metasediments intruded by Pan African Granites. Ten water samples were collected and analyzed in the laboratory to determine their chemical composition. The results revealed that the pH of most samples was slightly acidic to mainly alkaline, with high electrical conductivity (EC) and total dissolved solids (TDS) values. Correlation and regression analyses showed that the TDS, EC, salinity, chemical oxygen demand, dissolved oxygen, and major and minor constituents positively influenced the pH of the groundwater. Hierarchical cluster analysis demonstrated that the water samples had different compositions and concentrations based on local geological influences. The water samples from Granite, Quartzites, Migmatites and Gneiss rock types shared similar characteristics and had a lower concentration of minerals than the water samples taken from the Quartz Mica Schists and Metaconglomerates. The water in Igarra was predominantly Magnesium Bicarbonate type. However, some of the water samples exceeded the drinking standards for TDS, EC, Cl, Fe, Cr, Cd, and Pb. The study recommends the inclusion of biological parameters to gain a clearer picture of the water quality, particularly from the anthropogenic point of view.

Anisotropic mechanical properties of quartz mica schist subjected to true triaxial compression

Anisotropic mechanical properties of quartz mica schist subjected to true triaxial compression

A detailed study of the CHN-BQ rock mass classification method and its correlations with RMR and Q system and Hoek-Brown criterion

A CHN-BQ method is firstly defined to present the system and connotation of the current Chinese national standard “Standards for Engineering Classification of Rock Mass” GB/T 50,218. The core idea and content of the CHN-BQ method are studied in detail. Based on a qualitative classification of rock masses at the sites of in situ rock deformation and shear strength tests with a total number of 1439 test sets in nearly 90 projects, the statistical characteristics of in situ test results of different grades of rock mass are analyzed; Thus, the mechanical parameters corresponding to each grade of rock mass basic quality are proposed. Based on 997 groups of various rock mass classification data in 10 projects, the comprehensive CHN-BQ method verifies, and some essential remarks are obtained. Firstly, the 312 sets of parallelly measured data show that the consistency of less than one-grade discrepancy of the qualitative and quantitative classification in the CHN-BQ method is up to 71% in percentage. Secondly, a highly linear correlativity of the CHN-BQ method with the RMR method is found, and a linear regression equation is proposed. Thirdly, a logarithmic regression equation between the CHN-BQ method and the Q system is obtained, and equivalent grading divisions of the Q system from 9-level intervals towards traditional 5-level intervals are proposed. Finally, the research shows that the GSI concept in the Hoek-Brown criterion and the qualitative classification of rock mass structure in the CHN-BQ method are essentially coincident. Based on the measured data in quartz mica schist rock of an arch dam project, a linear regression equation of the Kv index in the CHN-BQ method and GSI index in the Hoek-Brown criterion is obtained, and the comparison of the strength parameters of the CHN-BQ method and Hoek-Brown criterion is discussed.

Characterizing a weathering profile over quartz-mica schists in undulating terrain in Peninsular Malaysia

The weathering profile can be differentiated into an upper, 4.8 m thick, pedological soil (zone I) and a lower, &gt;16.2 m thick, saprock (zone II). Zone I comprises thin IA and IB soil horizons of firm, clayey sand with lateritic concretions, and a IC soil horizon of stiff, clayey silt with quartz clasts and lateritized core-stones. Zone II comprises steeply dipping to vertical, bands of pinkish to grey, stiff silt with distinct relict foliation (highly weathered schist) inter-fingering with bands of reddish yellow, firm clayey silt with indistinct foliation (completely weathered schist) towards its top, and bands of white to light grey, hard silt with distinct foliation (moderately weathered schist) towards its bottom. Lateral variations in abundance of differently weathered schist and preservation of fracture planes allow zone II to be separated into IIA, IIB and IIC sub-zones. The pedological soil (zone I) can be correlated with Class VI of standard rock mass weathering classifications, whilst the saprock sub-zones IIA, IIB and IIC are correlated with Classes V, IV and III, respectively. Silt fractions in the profile consist predominantly of sericite flakes, whilst the sand fractions are mostly of quartz grains and the clay fractions of mainly illite and kaolinite. Decreasing densities, unit weights and silt contents up the profile, but increasing porosities and clay contents, indicate increasing in situ alteration of the schist bedrock. Lowering of an unconfined groundwater table as a result of down-cutting by rivers in adjacent valleys is considered responsible for development of the weathering profile.

The formation and architecture of Penglai granite intrusion reservoir along the Tanlu strike-slip fault: Implications for basement exploration in the offshore Bohai Bay Basin, North China

The hydrocarbon in the basinal basement mostly occurs in the topmost of buried hills along the unconformity, while we present a special play in architecture with the oil-bearing in the lower geomorphic position at the Penglai buried hill. Based on the cores, thin sections, whole rock X-ray, physical property, well logging, and seismic data, we investigated the characteristics of the reservoirs of the Penglai oilfield and discussed the controlling of strike-slip activity, weathering, and lithology on the reservoir in this paper. The results show that the Penglai buried hill reservoirs were mainly distributed in the fractured and weathered granites. The quality of the reservoir is related to mechanics and weathering dissolution behavior among different rocks. The strong dextral strike-slip activity of the Tanlu strike-slip fault zone during the Paleogene resulted in the strong uplift of the Penglai buried hill and also provided the stress condition for tectonic fractures to develop. The dissolution of atmospheric water along the tectonic fractures further improved the reservoir’s physical properties during the nearly 30Ma exposure interval. Compared to granite rocks, mica quartz schist, with higher content of the femic mineral and lower content of feldspar, presents lower brittleness and less soluble minerals. Therefore, the relatively stronger of weathering resistance of mica quartz schist resulted in a higher ring-landform in buried hill geomorphology which surrounds the granite intrusion, controlling the special oil play in architecture with hydrocarbon accumulated in the lower-seated granite reservoir underlying the unconformity.

Early neoproterozoic supracrustal successions in the central Korean Peninsula: Implications for the paleotectonic history of East Asia

The Early Neoproterozoic supracrustal metasedimentary succession from the Paju–Yangju–Dongducheon area in the central Korean Peninsula is distributed along the northwestern margin of the basement gneisses in the Middle Paleoproterozoic Gyeonggi Massif. The metasedimentary succession includes quartzite, quartz–mica schist, mica schist, calc schist, marble, and calc-silicate, showing alternating layering and large-scale isoclinal folds with Middle Paleoproterozoic gneisses. The basement gneisses yield zircon LA–MC–ICPMS U-Pb ages of 1.87–1.86 Ga. Detrital zircon U-Pb ages of eight quartzites, seven quartz–mica schists and four calc schists suggest the following features. (1) Early Neoproterozoic (ca. 0.92 Ga) sedimentation, (2) prominent age peaks in the Late Paleoproterozoic to Mesoproterozoic range, (3) sandy proximal and muddy to calcic distal provenances, and (4) age population under extensional and trailing edge settings. The detritus of the quartzites were mainly derived from the peripheral Middle Paleoproterozoic basement. In contrast, quartz–mica schists and calc schists show detritus derived from distal Late Paleoproterozoic to Mesoproterozoic clastic sources in the southeastern North China Craton and central Korean Peninsula where magmatic rocks related to the extensional tectonics associated with the disruption of the Columbia supercontinent occur. The detrital zircon records and litho-tectonic features indicate that the Early Neoproterozoic rocks in the Paju–Yangju–Dongducheon area, as well as the central Korean Peninsula, show similarities with the southeastern North China Craton. We therefore interpret that the Early Neoproterozoic supracrustal metasedimentary successions were deposited in marginal shallow marine to fluvial environments from the marginal part of the linked central Korean Peninsula and the southeastern North China Craton which were located at the southwestern margin of western part of the Columbia supercontinent during the Early Neoproterozoic (ca. 0.92 Ga). However, metamorphic overgrowths on zircons and large-scale isoclinal folding in the alternation of the Early Neoproterozoic metasedimentary and the Middle Paleoproterozoic rocks in the Paju–Yangju–Dongducheon area are related to Late Permian to Triassic compressional collision tectonics in the central Korean Peninsula after the Early Neoproterozoic sedimentation.

Revisiting the Late Paleozoic–Mesozoic tectonic evolution of epicontinental eastern Central Asian Orogenic Belt on the basis of detrital zircon

The eastern Central Asian Orogenic Belt (CAOB) is a natural laboratory for studying and interpreting the evolution of accretionary collages. The CAOB contains several micro-landmasses whose tectonic evolution during the Late Paleozoic–Mesozoic is a matter of debate. Here, we revisited detrital zircon data in relevant areas and present new detrital zircon U–Pb age data from the Hulin Complex and Wandashan Accretionary Complex (consisting of the Raohe and Yuejinshan complexes) in the eastern CAOB. The youngest zircon peak age of mica-quartz schist from the Hulin Complex constrains the timing of deposition to after ∼153.5 Ma. Sandy slate and fine sandstone from the Wandashan Accretionary Complex have youngest ages of ∼135.7 and ∼254.7 Ma, respectively. These data, together with detrital zircon data in the epicontinental eastern CAOB, suggest that there was a transformation from an extensional to convergent tectonic setting in the eastern CAOB around the Late Permian–Early Triassic. The Khanka Massif may have been adjacent to the Songnen and Jiamusi massifs to the west and north respectively, during the Late Paleozoic–Mesozoic. Between the Songnen and Jiamusi massifs, the Mudanjiang Ocean initially opened in the Late Paleozoic and closed after the Late Jurassic (∼153.5 Ma) and produced the Heilongjiang Complex. The Paleo-Yuejinshan back-arc basin underwent extension in the Permian and finally closed after ∼216 Ma, forming the Yuejinshan Complex at ∼210–180 Ma. The Raohe Complex was accreted at ∼169–133 Ma and emplaced at ∼133–131 Ma. The large-scale sinistral strike-slip movement of the Dunmi Fault started later than ∼153.5 Ma and partially displaced the Heilongjiang Complex from the Mudanjiang area to the present-day Hulin Complex. The eastern CAOB was under a superimposed tectonic regime of the Paleo-Pacific Ocean and Paleo-Asian Ocean in the Late Paleozoic.

Morphological attributes, petro chemistry and origin of quartzite units in Ekiti, South-Western Nigeria

This study presents lithologic and petrogenetic investigation of bedded quartzite from Okemesi and massive quartzites from Ado-Ekiti in southwestern Nigeria. Okemesi quartzite is extensive, thickly bedded and steeply dipping while quartzite from Ado-Ekiti is hummocky, ferruginous, fractured, and non-bedded. Analytical results reveal average SiO2 Okemesi (94.74 %) and Ado-Ekiti quartzite (93.88%). Similarly, average Rb/Sr are 0.74 and 1.22 while Sr/Ba are 0.89 and 0.69, respectively. These parameters portray them as supracrustal rocks of continental origin. Implying quartzites in Ekiti are non-schistose pelitic metasediments. Na2O/Al2O3 versus K2O/Al2O3 diagram revealed the quartzite units are sedimentary in origin and are compositionally similar to the Scottish metapelite and Igarra quartz mica-schist. Chemical Index of Alteration (CIA) of Okemesi quartzite (88 %) and Ado-Ekiti quartzite (91 %) which are relatively high signifies intense chemical weathering of their source rocks. Index of compositional variability (ICV) of Okemesi quartzite (0.83) and Ado-Ekiti quartzite (0.74) indicate the quartzites are immature pelite.

Geophysical assessment for gold mineralization potential over the southern part of Kebbi State using aeromagnetic data

The magnetic signatures over the southern part of Kebbi State and its environs were analyzed together with the geological settings of the area to delineate the structures that may host gold mineralization. The aeromagnetic data used was the survey carried out by Fugro airborne surveys between 2005 and 2010 on behalf of the Federal Government of Nigeria. The reduction to equator (RTE), first and second vertical derivatives (FVD and SVD), Centre for Exploration Targeting (CET), analytic signal (AS), source parameter imaging (SPI) and tilt derivative (TDR) techniques were applied to the magnetic data covering the area. The results of the AS technique revealed that the study area is characterized with high amplitudes of magnetic anomalies (above 0.048 nT/m) and these could be of ferromagnetic minerals such as gold. The FVD, SVD, CET and TDR techniques also helped in delineating the lineaments (such as faults, fractures or shears zones) believed to be associated with alteration zones which play an important role in determining gold mineralized zones. The direction of the orientation of these features/lineaments trended in the NE-SW direction. The faults, fractures or shears zones delineated represent veins of possible mineralization. The depth of occurrence to the causative bodies using SPI algorithms was found to be below 137 m. Structures delineated within the area, when compared with the geological setting of the area, correspond to quartz-mica schist, granite, biotite, gneiss, diorite, medium coarse-grained and biotite hornblende granite. Results from these techniques revealed alteration zones that may host gold. These regions correspond to the following areas: SE parts of Yauri and Shanga, Fakai, Ngaski, Zuru, Magama, Rijau, and the eastern part of Wasagu/Danko and Bukkuyum.

Geology and Structural Studies of Precambrian Basement Rocks Around Mahuta, Zuru Schist Belt, Northwestern Nigeria

The study of geology and structures in part of Zuru schist belt northwestern Nigeria was aimed at understanding the rock units, mineralogy, structural configuration, distribution and deformation. This was achieved through lineament analysis, petrographic study and structural analysis (geometric, kinematic and dynamic). Lineament analysis revealed the distribution, relative abundance and orientations of linear-curvilinear features. Three (3) main lithologic units were revealed; medium-grained granite, quartz-mica schist, and quartzite while minor ones are quartz vein, quartzofeldspathic pegmatite and aplitic dyke; this was arrived at because of minerals assemblages like quartz, feldspars, biotite, and muscovite. Structural analysis revealed the presence of normal fault, strike-slip fault and systematic joint (orthogonal). The joints trend is dominantly NE-SW, N-S, E-W. The normal faults reveal maximum principal stress (σ1) orientation in 087, the intermediate stress (σ2) was oriented in 222 while the minimum stress (σ3) was oriented in 312 directions. The kinematic axes revealed from the fault data are P-axis (Compressional) is 87/087; B-axis (Tensional) is 02/222 while T-axis (Transpressional) is 02/312. The component of deformation of the normal fault is elongated by 10-30 cm, while the vertical deformation effect is neutral. The area experienced multiple phases of deformation. The study will aid in mineral exploration.

Influence of Elevation on Slake Durability Index of Quartz Mica Schist: A Case Study of East Slope of Manjiazhai Open Pit

In order to study the influence of elevation on the slake durability index of the quartz mica schist, the quartz mica schist with different elevations on the east slope of the Manjiazhai open-pit mine is taken as the research object, and based on laboratory tests and statistical analysis, the variation of negative correlation between the slake durability index and elevation is obtained. The disintegration mechanism of quartz mica schist at different elevations is also discussed. The test results show that the disintegration characteristics of quartz mica schist at different elevations are related to its mineral composition, fissure channel size, and rock damage effect. As the slope height increases, the ratio of mica to quartz in the rock increases, and the greater the porosity of the rock, the more fissures in the rock, the greater the permeability coefficient, and the more obvious the change of effective stress of rock under osmotic pressure. At the same time, the higher the slope elevation of open-pit mine, the longer the weathering time of rock, the higher the cumulative damage of rock, and the lower the rock slake durability index. This study provides a new idea for guiding the research on the disintegration characteristics of similar soft rock slopes in the elevation direction.

УЛАМКИ ЕКЗОТИЧНИХ МЕТАМОРФІЧНИХ СЛАНЦІВ В ОЛІГОЦЕНОВИХ ВІДКЛАДАХ СІЛЕЗЬКОГО ПОКРИВУ (УКРАЇНСЬКІ КАРПАТИ)

The study aims at analyzing the petrographic composition of exotic metamorphic schist clasts in the Oligocene deposits filling the Silesian Nappe in the south-western part of the Ukrainian Carpathians and reconstructing their possible source area. The methodology includes petrographic, sedimentological and comparative geological methods. To achieve this goal, field research was carried out along the first right tributary of the Hysnyi Stream (the village of Uzhok, Velykobereznyanskyi district, Transcarpathian region) and petrographic analysis of the selected samples of the exotic metamorphic schist clasts included in the Oligocene debris-flow deposits was performed. The results of microscopic studies showed that these exotic rocks are represented by mica-quartz schist and garnet-muscovitebiotite-plagioclase-quartz schist with a low content of chlorite, carbonate and epidote. Mineral composition and structure/texture features suggest the rocks were metamorphosed under green schist and epidote-amphibolite facies. Similar exotic rock fragments were identified by Polish scientists in the south-eastern part of the Polish Carpathians in the Silesian Nappe, where possible source area of the exotic rocks is related to the Bukowiec Paleo-Ridge, which had been located between the Dukla and Silesian basins of the Carpathian sedimentary realm. Scientific novelty. For the first time, the petrographic composition and textural and structural features of the exotic schists fragments included in the Oligocene deposits of the Silesian Nappe in the Ukrainian Carpathians (area of the village of Uzhok, Ukrainian Carpathians) are described. These schists are similar to the exotic rocks included in the Oligocene deposits of the Silesian Nappe in the Polish Carpathians, which may indicate the same source area.