Quartz Schist Research Articles

Variation of some soil properties along two toposequences on quartzite schist and banded gneiss in Southwestern Nigeria

Samples were taken at 0–15 cm, 15–30 cm and 60–90 cm at 15 m interval from the crest to the valley bottom of two toposequences, one on quartzite schist and the other on banded gneiss within the same microclimate. Variations in pH, colour, (hue, value and chroma) particle size fractions, gravimetric moisture, gravel and CEC were examined. Soil pH was the least variable (cv = 3–5%) irrespective of depth or toposequence. The highly variable properties were silt (cv = 34–106%), CEC (cv = 22–101%), moisture (cv = 33–67%), clay (cv = 30–66%) and colour chroma (cv = 26–62%). Some of the properties (eg subsoil clay) show distinct regions while many properties show no discernible pattern along the toposequence (eg coarse sand). The quartz schist toposequence showed higher variation than the banded gneiss. The two toposequences were more similar near the soil surface (0–30cm) than in the subsoil (60–90cm). Clustering of points by property values along the toposequence and using the clusters that are common to the highest number of soil properties produced 3–4, and 4 homogeneous regions at 0–30cm and 60–90cm respectively along the toposequences.

The Petrophysics, Geophysics and Structure of the Koongarra Site, Northern Territory

This paper reports on part of a natural analogue study on the migration of radionuclides in the weathered zone at the Koongarra site in the Northern Territory of Australia. The unmined but intensively drilled Koongarra uranium deposit in the Northern Territory of Australia has been studied to evaluate the processes and mechanisms involved in the alteration of the primary uranium mineralisation and to model the formation of the secondary uranium orezone and the dispersion fan. The work has resulted in solid phase and groundwater databases, and hydrological data from field and laboratory measurements. These are being used to test a range of geochemical, hydrological and transport models. The Koongarra uranium deposit is situated in the Alligator Rivers Uranium Province of the Northern Territory of Australia, about 200 km east of Darwin. The uranium ore is located in steeply dipping, physically anisotropic, quartz chlorite Cahill Formation schists of early Proterozoic age and is near the base of a prominent southeast-facing sandstone escarpment. The upper 25 m of the schist is weathered. An upper clayey zone of intense weathering separates deeper partly weathered schist from the overlying Quaternary sands, silts and ferricretes. Directly to the northwest of the ore deposit, a major reverse fault, the Koongarra Fault, has upfaulted the schist against the middle Proterozoic Kombolgie Sandstone. Hydraulic properties of the fault zone have not been tested directly, but the fault was previously considered to be a barrier or partial barrier to lateral flow of groundwater. The site is currently undisturbed by mining, but the steel casings of over 100 exploratory drillholes proved to be a source of noise in magnetic and electrical surveys and the condition of the holes precluded the use of drillhole and cross-hole geophysics in the site studies. A number of different approaches have been made to characterise the site and to try to understand: how groundwater has moved and is moving through the orezone region; the source of the water ? natural recharge or flow across the fault; how the groundwater drains out of the site; whether fluid flow is through fractured or porous media or both; and in particular, how this has influenced the transport of uranium and the formation of a prominent dispersion fan.

Sedimentational, structural and migmatitic history of the Archaean Dharwar tectonic province, southern India

The earliest decipherable record of the Dharwar tectonic province is left in the 3.3 Ga old gneissic pebbles in some conglomerates of the Dharwar Group, in addition to the 3.3–3.4 Ga old gneisses in some areas. A sialic crust as the basement for Dharwar sedimentation is also indicated by the presence of quartz schists and quartzites throughout the Dharwar succession. Clean quartzites and orthoquartzite-carbonate association in the lower part of the Dharwar sequence point to relatively stable platform and shelf conditions. This is succeeded by sedimentation in a rapidly subsiding trough as indicated by the turbidite-volcanic rock association. Although conglomerates in some places point to an erosional surface at the contact between the gneisses and the Dharwar supracrustal rocks, extensive remobilization of the basement during the deformation of the cover rocks has largely blurred this interface. This has also resulted in accordant style and sequence of structures in the basement and cover rocks in a major part of the Dharwar tectonic province. Isoclinal folds with attendant axial planar schistosity, coaxial open folds, followed in turn by non-coaxial upright folds on axial planes striking nearly N-S, are decipherable both in the “basement” gneisses and the schistose cover rocks. The imprint of this sequence of superposed deformation is registered in some of the charnockitic terranes also, particularly in the Biligirirangan Hills, Shivasamudram and Arakalgud areas. The Closepet Granite, with alignment of feldspar megacrysts parallel to the axial planes of the latest folds in the adjacent schistose rocks, together with discrete veins of Closepet Granite affinity emplaced parallel to the axial planes of late folds in the Peninsular Gneiss enclaves, suggest that this granite is late-tectonic with reference to the last deformation in the Dharwar tectonic province.

Consolidation and Permeability of Two Compacted Schist Saprolites

Saprolites derived from a mica schist and a quartz schist from southwestern Nigeria are compacted at three energy levels, namely 0.6 MNm/m3, 1.1 MNm/m3, and 2.7 MNm/m3, and subjected to consolidation and permeability tests. Despite their high mica contents—25% and 30%, respectively—the saprolites attained fairly high maximum dry densities (1.68–2.04 t/m3). For each saprolite, increased compaction energy reduced compressibility appreciably but caused virtually no difference in permeability; the quartz schist saprolite being less compressible and less permeable than the mica schist saprolite. The compressibilities varied from low to very low while the saprolites have very low permeability for all the compaction energies. Comparison of the results of these tests on this mica schist saprolite with those of mica schist saprolites obtained from high horizons shows that the mica schist saprolite used in this study is better suited for use as subbase and fill material.

Development of microboudinage: an estimate of changing differential stress with increasing strain

Microboudin structure has so far been used in structural analysis as a reliable measure of plastic strain, and recently it has been proposed to use it as a measure of relative differential stress. This paper demonstrates that stress and strain can be simultaneously deduced if the stress and strain analyses are carried out in combination. The analysed samples are quartz schists from four localities of different high P/ low T type metamorphic belts in Japan. The samples include microboudinaged competent piedmontite grains within a ductile quartz matrix. The analyses strongly suggest that the estimated differential stresses tend to increase with increasing strain and that, at the final stage of the microboudinage, they reach a maximum.

Mn-rich amphiboles from quartz schists of the Iimori district Sambagawa terrane, Wakayama.

Calcic to sodic amphiboles rich in Mn have been found in association with Mn-rich sodic pyroxenes and spessartine garnets in quartzose schists of the Sambagawa terrane of the limori district, Wakayama Prefecture, Southwest Japan. The amphiboles range in composition from subcalcic tremolite through winchite to crossite. One of the amphiboles is tirodite, as it has considerably high content of MnO (14.27 wt. %).

Microboudin structure of piedmontite in quartz schists: a proposal for a new indicator of relative palaeodifferential stress

This paper proposes a new method to infer the relative differential stress for the rock body (bulk differential stress) from microboundinage. The method is applied to four piedmontite-bearing quartz schists collected from the high-pressure/low-temperature metamorphic belts in Japan (Nuporomaporo, Yamagami, Asemi and Matsunosako). In the samples, brittle piedmontite grains are broken and subsequently pulled apart within the flowing quartz matrix. The method consists of (1) statistical measurement of the fraction of microboudinaged grains (2) theoretical prediction of this fraction as a function of bulk differential stress and (3) inference of bulk differential stress by comparing the measured with the theoretical fraction. The theoretical prediction has two aspects: one is the model connecting bulk differential stress acting on a whole rock (quartz schist) with the tensile stress generated in the competent material (piedmontite), and the other is the model for the fracture strength of the competent material. We use a fibre-loading theory for the stress and a weakest-link theory for the fracture strength. The theoretical analysis is found to explain successfully the measured data by a chi-squared test, and we can obtain relative estimates of bulk differential stress (the B value); they are 1.0, 0.7, 0.4 and 0.2 for Nuporomaporo, Yamagami, Matsunosako and Asemi, respectively.

Offshore continuation of Meguma Terrane, southwestern Nova Scotia

Eight short drill cores have been examined from the continental shelf southwest of Nova Scotia. Four cores recovered granitoid rocks of two types. Ilmenite-bearing granitoid rocks petrographically and geochemically resemble granodiorites of the South Mountain Batholith and granites of the Seal Island Pluton. Magnetite-bearing granitoid rocks are also peraluminous but have no exact analogues onshore in Nova Scotia. Two cores recovered metamorphic rocks in a small area 50 km south of Seal Island. One consits of chlorite–muscovite–quartz schist, geochemically similar to rocks of the Halifax Formation. The second sampled epidote–chlorite–quartz schist similar to metavolcanic rocks of the White Rock Formation. One further core sampled quartzite, and another sampled a metavolcanic rock (possibly erratic).The regional extent of these lithotypes can be inferred from gravity and aeromagnetic data. Regional gravity data suggest the presence of a large granite body off southwestern Nova Scotia. In this area, magnetic anomalies are irregular, apparently reflecting the presence of magnetite-bearing granites. The layer-stripping method of analyzing the magnetic field shows that the area is underlain at depth by high magnetic anomalies. Large near-surface linear magnetic anomalies are used to map the extent of the volcanic rocks of the White Rock Formation. The area is cut by several northwest-trending faults that postdate Acadian folding but predate the earliest Jurassic magmatism of the Shelburne Dyke and North Mountain basalt. The unusual magnetic signature of the area off southwestern Nova Scotia may reflect a different basement; it is possible that Meguma rocks are thrust over the Avalon Terrane. Alternatively, it may be solely the result of magnetite-bearing granites. These granites may be related to a Permian thermal event in southwest Nova Scotia, and they have some petrographic similarity to young granites of the Piedmont Zone of South Carolina.

Successive “mid-point” fracturing during microboudinage: an estimate of the stress-strain relation during a natural deformation

This paper describes a piedmontite microboudinage during plastic flow of surrounding quartz in a quartz schist, collected from the high pressure/low temperature Sambagawa metamorphic belt in southwest Japan. Nine microboudins originated from a single grain by successive “mid-point” fracturing and subsequent “pull apart”. Such features strongly indicate a fibre-loading mechanism for the microboudinage. The strain history inferred by successive use of the strain reversal method and stress data quantitatively calculated by a formula of the fibre-loading theory provide us with an estimate of the stress-strain relation during the microboudinage. It apparently proceeded with increasing bulk stress during the last stage of metamorphism.

Basic geotechnical properties, chemistry and mineralogy of some laterite soils from S.W. Nigeria

Laterite soils derived from four basement complex rocks and a sedimentary formation from Southwestern Nigeria are analysed for their basic geotechnical properties, chemistry and mineralogy. Results obtained show that the granite gneiss derived and the sedimentary laterite soils are good engineering materials. The amphibolite derived laterite soil has a linear shrinkage of 10% and contains SO42− ions. The quartz schist derived and the micaschist derived laterite soils contain rather high amounts of muscovite −30% and 25% respectively.

四国三波川帯変成マンガン鉱床からのアルデン石とソーサ石の産出

Ardennite and sursassite have been found in the outcrop of the Hakuryu mine, Tokushima Prefecture, being a metamorphic manganese deposit of the Muramatsu type, and also as boulders in the Kamogawa river, Ehime Prefecture. They are embedded in piemontite bearing quartz schists in the Sanbagawa belt. The ardennite and the sursassite show two different occurrences. One is observed in layers of fine crystal aggregates, with quartz, spessartine, chlorite, piemontite and braunite, and the other is in veinlets cutting a quartz-braunite-piemontite ore. Both minerals associate with each other and sometimes show parallel intergrowths. The ardennite is yellowish brown or golden yellow and the sursassite is reddish brown in color. They are subhedral, or euhedral crystals up to 5 mm in length and are chemically heterogeneous. The ardennites are characterized either by high V or As contents, and also by high SiO2 content. The Hakuryu sursassite is rich in manganese in comparison with that of Kamogawa, and shows extensive substitution of Mn and Fe for Al, and of Ca for Mn.

Ardennite in a quartz schist from the Asemi-gawa area in the Sanbagawa metamorphic terrain, central Shikoku, Japan.

Ardennite is found to occur in a piemontite-bearing quartz schist from the Asemigawa area in the Sanbagawa metamorphic terrain, central Shikoku. The ardennite-bearing quartz schist contains quartz, piemontite and garnet as major constituents with subordinate amounts of talc, chlorite, albite, calcite, hematite, braunite, rutile and apatite, together with ardennite. Ardennite is pale golden yellow and occurs as subhedral and prismatic crystals up to 1 mm in length. It is optically positive with 2VZ=57±3°. It is orthorhombic and unit cell parameters are a=5.828(2) A, b=18.540(8) A, c=8.692(3) A and V=939.1(6) A3. As2O5 and V2O5 contents of ardennite reach 10.8 and 1.3 wt.% in maximum, respectively. The empirical formula of the ardennite is (Ca0.53Mn3.67)(Mg1.02Cu0.03Fe0.203+Al4.47Ti0.01)(As0.80V0.09) Si5.25O22 (OH)6. It is slightly poor in (As + V) and rich in Si compared with the ideal formula of ardennite. Piemontite contains SrO of 0.7wt.% in maximum.

Gandhara sculptural schist: Proposed source

Previously suggested source localities for the chloritoid-paragonite-muscovite quartz schist, the most widely used Gandharan rock, have been examined and rejected. However, an ancient disused quarry near Sakhakot, south of Dargai, in northern Pakistan, has been located and sampled. Chemical and mineralogical comparisons between two quarry samples and a specimen of artifact schist are very close, leading to the proposal that the quarry is one definite source of Gandhara sculptural schist.

General geology and petrography of the precambrian basement around Zalingei town, Darfur Province, Sudan

Abstract The exposed Precambrian rocks of the greater Zalingei area consisted originally of a thick succession of psammites and semipelites. The upper exposed part of this succession included some probable bituminous intercalations that are now represented by graphitic quartz schists. The succession also contained few carbonate beds and minor intrusions of dolerite. The entire succession had later suffered a major protracted cycle of tectonic deformation, regional metamorphism and migmatism. The metasediments were open-folded into synforms and antiforms that now have ENE-WSW axial trends. The migmatites around Zalingei town display repeated events of deformation and recrystallization, as well as partial melting. Earlier metamorphic assemblages point to granulite facies conditions (sillimanite, orthorhombic pyroxene) but these assemblages were largely replaced by later amphibolite facies minerals (kyanite, staurolite, almandite, hornblende). Partial melting accompanied by extensive flow-folding on all scales affected the more susceptible semipelites and produced a wide variety of migmatitic gneisses. At first these migmatites were oligoclasic and produced melt segregates and small syntectonic injections of trondhjemite, tonalite or granodiorite. Later, more potassic migmatites evolved, mainly through microclinization of the earlier migmatites. A monzogranitic intrusion with very large porphyritic potash feldspars was also mobilized from a lower crustal level. A further episode of some strong deformation followed and left a variable foliate and rather erratic imprint on the different rocks. This deformation might have accompanied the uprise of intrusive granitoid diapirs mantled from outside by diverse concentrically foliated gneisses with boudinaged minor pegmatite intrusions. The diapirs have inner massive central cores of leucocratic monzogranites and their intrusion ended the major plutonic activities. Quartz—tourmaline veinlets and massive dyke-like bodies accompanied and survived the diapir intrusions and represented the terminal penumatolytic and hydrothermal stages. The large quartz dykes, the master-joints and other late lineaments are crudely oriented in a NW-SE trend. From apparently similar lithologies and geologic events in the adjacent basement rocks of Eastern Chad and the Central African Republic, the original age of the Zalingei sedimentary succession is provisionally assigned to Precambrian D (older than 2500 Ma). The migmatitic to late diapiric activities, however, represented reactivation (rejuvenation) of the basement rocks as the Zalingei basement falls within the broad NE-SW mobilized belt running between the West African and Congo cratons in Pan-African times (500–600 Ma).

A Microstructural sequence of quartz schists in central Shikoku, south-west Japan

This paper describes a microstructural sequence of quartz schists (metamorphosed chert) in the Asemi river region of the Sambagawa metamorphic terrain in central Shikoku, southwest Japan. The Asemi river region is divided into three areas on the basis of characteristics of microstructures of quartz schists observed under the optical microscope: areas I, II and III, in ascending order of metamorphic grade. Microstructures in area I consist of finer, equant, equidimensional and polygonal quartz grains free from internal deformation features. Microstructures in area II are characterized by oblate or elliptical grains with remarkable undulatory extinction surrounded by serrated grain boundaries. Microstructures in area III consist mainly of coarser and equant grains without distinct internal deformation features. The formation conditions of these microstructures are discussed in the light of recent experimental results.

Provenance and Depositional Mode of Upper Cretaceous Chatsworth Formation Conglomerates, Simi Hills, California: ABSTRACT

Conglomerates of the Upper Cretaceous Chatsworth Formation occur as lenses of concentrated clasts in channels and as clasts dispersed at the base of thick, coarse-grained, graded sandstone beds. The matrix of the conglomerates consists of grains ranging from silt to granule size (4 mm) and comprises between 20 and 78% of any one conglomerate unit. The matrix composition ranges from 30 to 80% quartz, 25 to 60% feldspar, and 5 to 20% lithic fragments, with accessory biotite up to 5%. The conglomerate clast population is composed principally of clasts in the pebble size range. Five distinct rock types are recognized within the conglomerate clast population: blue-black argillite, 4 to 20%; felsic volcanites, 4 to 28%; felsic plutonites, 16 to 24%; arkosic sandstones and silts one, 0 to 12%; and a group of genetically related quartz-rich clasts, 17 to 46%. The quartz-rich clasts include sandstones and siltstones with continuous textural gradation from well-preserved sandstone through partially recrystallized sandstone with sutured grains, into metamorphosed, foliated quartz sandstone and quartz schist types. In addition, a conglomerate unit may contain between 0 and 14% authigenic rip-up clasts. The Chatsworth Formation, as a whole, is recognized to be a deep-sea fan complex upon which the primary depositional agent for sand was turbidity currents. Lenses of concentrated pebble conglomerates originated as debris flow, whereas beds of dispersed pebble clasts are of turbidity current origin. Paleocurrent data and the conglomerate clast composition for the Chatsworth Formation indicate that its detritus was derived from a source terrane to the south of the Simi Hills. The Santa Monica Mountains basement complex contains a large mass of argillite and felsic plutonite, but contains no felsic volcanite or quartz-rich suite of rocks. The basement in the northern Peninsular Ranges includes representatives of the principal rock types recognized in the clasts of the Chatsworth Formation conglomerates and, therefore, it is the best possible choice for the provenance. Extensive Franciscan terrane also lies south of the Chatsworth conglomerates, but no Franciscan detritus is recognized in the Chatsworth Formation. End_of_Article - Last_Page 1686------------

Geology and Soil of Dhankuta area eastern Nepal

A geological map of 200 sq. km of Dhankuta area is presented. Mapped geological formations recognized include Dhankuta and Mulghat formations of Precambrian- Lower Paleozoic age. The Dhaukuta Formation comprises of garnet- biotite- muscovite- quartz schist and gneiss with conspicuous beds of grey and white quartzite. The Mulghat Formation is differentiable into three members and includes schistose phyllite and actinolite schist with carbonates, garnetiferous phyllite with sills of amphibolite, and phyllite and quartzite. The general strike of the formation is east west and dips northerly in order of 20° to 60°. The east- west trending Tamar fault passes to the south of Dhankuta Bazar. The nature of the soil present in Dhankuta Bazar is non-plastic and is formed by insitu weathering of the parent rock. The deep gullies are prominent feature caused by an intensive erosion and denudation of the soil and the instability of the surface could largely be attributed to this factor. A few stone quarries can be operated around Dhankuta Bazar for the supply of building and dimension stones to minimise the immediate brick problem.

WEATHERING IN TERTIARY GRAVELS IN N.E. SCOTLAND

SummaryThe weathering of highly quartzose flint‐containing gravels, believed to be the remnants of Tertiary beach deposits in N.E. Scotland, has been studied in detail. The deposits also contain infrequent boulders of granite, quartz schists and granulites which are largely kaolinised, but the kaolin varies in crystallinity between the two sites investigated. Quartz, alkali feldspars, muscovite and biotite‐like mica have been variously altered, and the weathering products include fine grained silica and leucoxene.

Notes on petrography and rock-forming mineralogy. 2. Find of a paragonite-bearing quartz schist from the Kotu district, eastern Shikoku.

Notes on petrography and rock-forming mineralogy. 2. Find of a paragonite-bearing quartz schist from the Kotu district, eastern Shikoku.

Kanonaite, (Mn 0.76 3+ Al0.23Fe 0.02 3+ )[6]Al[5][O�SiO4], a new mineral isotypic with andalusite

Kanonaite forms rare porphyroblasts up to 12mm long in a gahnite— Mg-chlorite — coronadite — quartz schist occurring near Kanona, Zambia. The composition is (microprobe analysis): SiO2 32.2, Al2O3 33.9, Mn as Mn2O3 32.2, Fe2O3 0.66, ZnO 0.13, MgO 0.04, BaO 0.04, TiO2 0.01, CaO 0.01, PbO 0.01, CuO 0.01, total 99.21, corresponding to $$\left( {{\text{Mn}}_{{\text{0}}{\text{.76}}}^{{\text{3 + }}} {\text{Al}}_{{\text{0}}{\text{.23}}} {\text{Fe}}_{{\text{0}}{\text{.015}}}^{{\text{3 + }}} } \right)_{1.005}^{\left[ 6 \right]} {\text{AL}}_{1.00}^{\left[ 5 \right]} \left[ {{\text{O}}_{{\text{1}}{\text{.00}}} |{\text{Si}}_{{\text{0}}{\text{.99}}} {\text{O}}_{{\text{4}}{\text{.00}}} } \right]$$ The mineral is greenish black, strongly pleochroic with X(∥a) yellow green, Y(∥b) bluish green, Z(∥c) deep golden yellow, biaxial positive, with 2V = 53°(3°), α = 1.702, β = 1.730, γ = 1.823. Vickers microhardness (100 gram load) ranges between 906 and 1017kp/mm2. The structure is orthorhombic, isotypic with andalusite, space group Pnnm, a = 0.7953(2), b = 0.8038(2), c = 0.5619(2) nm, V = 0.3592(1) nm3, a/b = 0.9895(3), c/b = 0.6990(3), S.G.(x) = 3.395 g/cm3, Z = 4. The strongest X-ray powder lines are (d in nm, I, hkl):0.5669, 100, 110; 0.4590, 75, 011 and 101; 0.3577, 90, 120 and 210; 0.2827, 94, 220; 0.2517, 90, 310 and 112; 0.2212, 83, 320, 122 and 212. Comparison of the intensities of 373 observed X-ray reflections with those calculated for several models of Mn3+-distribution indicates octahedral coordination of all or most of the manganese present. Interpretation of magnetic measurements (μeff = 3.15B.M. per Mn atom at 25 ° C) indirectly supports octahedral coordination of Mn3+. The name of the mineral is for Kanona, a town near the type locality. The name is proposed for the end member Mn3+[6]Al[5][O¦SiO4] and for members of the solid-solution series towards andalusite with octahedral Mn3+>Al. The presently described mineral may be referred to as aluminian kanonaite.