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.

New Insights into Pre-to-Post Ediacaran Zircon Fingerprinting of the Mamfe PanAfrican Basement, SW Cameroon: A Possible Link with Rocks in SE Nigeria and the Borborema Province of NE Brazil

The pre- to post-Late Neoproterozoic geological histories in the south to southwestern part of Mamfe Basin (SW Cameroon) were reported following analysis of the zircon crystals from their host rocks. A genetic model was developed for the zircon host rocks’ formation conditions, and the registered post-emplacement events were presented. The obtained ages were correlated with the data available for rocks in the Cameroon Mobile Belt, SE Nigeria, and the Borborema Province of NE Brazil. Separated zircons from Araru black to whitish gneiss, Araru whitish-grey gneiss, and Mboifong migmatite were analyzed for their morphology and texture U-Th-Pb composition, and U-Pb ages. Published U-Pb zircon ages for Otu granitic pegmatite, Babi mica schist, and Nkogho I-type anatectic granite were updated. Zircon ages in Araru black to whitish gneiss; Araru whitish-grey, Mboifong migmatite, Babi mica schist, Nkogho I-type anatectic granite, and Otu granitic pegmatite date the Eburnean tectono-magmatic/metamorphic event in Cameroon and SE Nigeria. The Late Paleoproterozoic to Early Mesoproterozoic ages record extensional (continental rift) settings and anorogenic magmatism in the Borborema Province in the NE of Brazil. These ages date collisional phases between the São Francisco–Congo and West African cratons and the Saharan metacraton with metamorphism and magmatism in Cameroon. They also date the Kibarian tectono-magmatic/metamorphism and PanAfrican tectono-magmatic/metamorphism in SE Nigeria. The Late Paleoproterozoic to Early Mesoproterozoic ages date the Cariris Velhos orogeny in the Borborema Province in NE Brazil, with Early Tonian crustal rifting, magmatism, and metamorphism and the collisional phase of the Brasiliano orogeny with syn-collisional plutons and extensive shear zoning and post-collisional granite intrusions.

Tabun Khara Obo impact crater, Mongolia: Geophysics, geology, petrography, and geochemistry

ABSTRACT Tabun Khara Obo is the only currently known impact crater in Mongolia. The crater is centered at 44°07′50″N and 109°39′20″E in southeastern Mongolia. Tabun Khara Obo is a 1.3-km-diameter, simple bowl-shaped structure that is well visible in topography and clearly visible on remote-sensing images. The crater is located on a flat, elevated plateau composed of Carboniferous arc-related volcanic and volcanosedimentary rocks metamorphosed to upper amphibolite to greenschist facies (volcaniclastic sandstones, metagraywacke, quartz-feldspar–mica schist, and other schistose sedimentary rocks). Some geophysical data exist for the Tabun Khara Obo structure. The gravity data correlate well with topography. The −2.5–3 mGal anomaly is similar to that of other, similarly sized impact craters. A weak magnetic low over the crater area may be attributed to impact disruption of the regional trend. The Tabun Khara Obo crater is slightly oval in shape and is elongated perpendicular to the regional lithological and foliation trend in a northeasterly direction. This may be a result of crater modification, when rocks of the crater rim preferentially slumped along fracture planes parallel to the regional structural trend. Radial and tangential faults and fractures occur abundantly along the periphery of the crater. Breccias occur along the crater periphery as well, mostly in the E-NE parts of the structure. Monomict breccias form narrow (<1 m) lenses, and polymict breccias cover the outer flank of the eastern crater rim. While geophysical and morphological data are consistent with expectations for an impact crater, no diagnostic evidence for shock metamorphism, such as planar deformation features or shatter cones, was demonstrated by earlier authors. As it is commonly difficult to find convincing impact evidence at small craters, we carried out further geological and geophysical work in 2005–2007 and drilling in 2007–2008. Surface mapping and sampling did not reveal structural, mineralogical, or geochemical evidence for an impact origin. In 2008, we drilled into the center of the crater to a maximum depth of 206 m, with 135 m of core recovery. From the top, the core consists of 3 m of eolian sand, 137 m of lake deposits (mud, evaporites), 34 m of lake deposits (gypsum with carbonate and mud), 11 m of polymict breccia (with greenschist and gneiss clasts), and 19 m of monomict breccia (brecciated quartz-feldspar–mica schist). The breccias start at 174 m depth as polymict breccias with angular clasts of different lithologies and gradually change downward to breccias constituting the dominant lithology, until finally grading into monomict breccia. At the bottom of the borehole, we noted strongly brecciated quartz-feldspar schist. The breccia cement also changes over this interval from gypsum and carbonate cement to fine-grained clastic matrix. Some quartz grains from breccia samples from 192, 194.2, 196.4, 199.3, 201.6, and 204 m depth showed planar deformation features with impact-characteristic orientations. This discovery of unambiguous shock features in drill core samples confirms the impact origin of the Tabun Khara Obo crater. The age of the structure is not yet known. Currently, it is only poorly constrained to post-Cretaceous on stratigraphic grounds.

The use of mica schist from Indonesia as raw material for lithium extraction process using sulfate roasting and acid leaching

Lithium minerals become a sub-economic raw material for lithium production to fulfill the lithium demand. This study is about lithium extraction from mica schist using the roasting and leaching processes. The mica schist located in Kebumen, Indonesia was used to study the phenomena during the lithium extraction process. Sodium sulfate was used as a roasting agent while 0.36 M sulfuric acid was used as a leaching agent. Solid/liquid ratio (1:5, 1:10, 1:15 and 1:20 (g/mL)) and leaching time (30, 60, 90 and 120 minutes) were used as variables in this study. The roasting process was done at 700 °С for 40 minutes while the leaching process was done at 70 °С and 350 rpm. The ratio of additive and mica schist was 1.5:1 (g/g). XRD, ICP-OES, and SEM were used to observe the formed compounds, chemical composition and morphology of the materials. HighScore Plus (HSP) was used to interpret the content of each compound in mica schist, roasted mica schist, and residue. ICP analysis confirmed that the mica schist contains 45.28 ppm of lithium. It is supported by XRD that lithium exists in mica schist as lepidolite (KLi2AlSi4O10(F,OH)2). Sulfate roasting did not affect the type of lepidolite but the lepidolite reactivity against the chemical agent. SEM analysis shows that the roasting process reduced the average particle size from 32.17 to 27.16 µm. ICP analysis of roasted mica schist shows that lithium concentration was reduced from 45.28 to 1.27 ppm. The optimum result from this study was 97.66 % extraction of lithium while solid/liquid ratio was 1:5 (g/ml) and leaching time was 30 minutes. HSP shows that lepidolite contents in initial mica schist, roasted mica schist and residue were 60.6; 24.3 and 18.7 %, respectively. Lithium concentration in the residue according to ICP analysis is 1.06 ppm.

Development of a New Empirical Relation to Assess P-wave Velocity Anisotropy of Rocks

Wave velocity as a simple nondestructive method is used for various applications in geotechnical engineering. Several physical parameters and anisotropy related to rock textural arrangements, schistosity and weakness planes such as cracks and joints affect the P-wave velocity (VP). First, VP anisotropy of quartz-mica schist as a common type of widespread metamorphic rock was compared with VP anisotropy of jointed homogeneous limestone specimens to clarify effect of these two different types of anisotropies. The results showed that the VP anisotropy of quartz-mica schist texture is stronger than the VP anisotropy of jointed limestone, because all body of quartz-mica schist specimens have VP anisotropy behavior. Many rocks are anisotropic and degree of anisotropy varies from one rock to another. Several investigations have been carried out on VP anisotropy but there is not a unique comprehensive relation to represent the influence of different degrees of anisotropy on the VP for different rocks. The relation between VP and angle (θ) between the axis of symmetry (perpendicular to weakness planes) with the wave propagation direction was analyzed for a wide range of anisotropy degree using the results of nine different types of rocks including: Angouran quartz-mica schist, Golgohar mica schist, amphibole schist, mica-quart schist, Marcellus shale, Withby shale WUK47B, WUK70 and WUK2, and Veroia-Polymylos gneiss. A new simple empirical relation fitted to all groups of results was obtained to assess VP for different degrees of anisotropies with a good correlation of determination (R2 = 0.937), low RMSE (RMSE = 320 m/s) and low CV (CV = 7.0%). P wave velocity anisotropy can simply be predicted by the developed relation using only two parameters of VP0 and VP90. A VP anisotropy classification diagram was also developed based on the different values of ε.

Contrasting metamorphic and post-metamorphic evolutions within the Algyő basement high (Tisza Mega-unit, SE Hungary). Consequences for structural history

The Algyő High (AH) is an elevated crystalline block in southeastern Hungary covered by thick Neogene sediments. Although productive hydrocarbon reservoirs are found in these Neogene sequences, numerous fractured reservoirs also occur in the pre-Neogene basement of the Pannonian Basin. Based on these analogies, the rock body of the AH might also play a key role in fluid storage and migration; however, its structure and therefore the reservoir potential is little known. Based on a comprehensive petrologic study in conjunction with analysis of the spatial position of the major lithologies, the AH is considered to have been assembled from blocks with different petrographic features and metamorphic history. The most common lithologies of garnet-kyanite gneiss and mica schist associated with garnetiferous amphibolite are dominant in the northwestern and southeastern parts of the AH. The first regional amphibolite facies metamorphism of the gneiss and mica schist was overprinted by a contact metamorphic (metasomatic) event during decompression in the stability field of kyanite. Garnet-bearing amphibolite experienced amphibolite facies peak conditions comparable with the host gneiss. Regarding the similarities in petrologic features, the northwestern and southeastern parts of the area represent disaggregated blocks of the same rock body. The central part of the AH area is characterized by an epidote gneiss-dominated block metamorphosed along with a greenschist-facies retrograde pathway as well as a chlorite schist-dominated block formed by greenschist-facies progressive metamorphism. The independent evolution of these two blocks is further confirmed by the presence of a propylitic overprint in the chlorite schists. The different metamorphic blocks of the northwestern, southeastern and central parts of the AH probably became juxtaposed along post-metamorphic normal faults developed due to extensional processes. The supposed brittle structural boundaries between the blocks could have provided hydrocarbon migration pathways from the adjacent over-pressured sub-basins, or could even represent suitable reservoirs.

Tectonostratigraphy of the Southernmost Scandinavian Caledonides: testing the Shetland correlation and the Laurentian/Renlandian link

<p>Geological mapping, zircon U–Pb dating of 28 samples, and mica <sup>40</sup>Ar–<sup>39</sup>Ar dating of 7 samples in the Stavanger–Ryfylke region (Stavanger, Suldal, Nedstrand, Randøy) characterizes the tectonostratigraphy of the southernmost nappes in the Scandinavian Caledonides. Four main tectonostratigraphic levels are described. (1) The lowest phyllite/mica schist nappes –Buadalen, Holmasjø, Lower Finse, Synnfjell– represent the Cambro–Ordovician sediment cover of the Baltic margin. (2) The overlying nappes –Madla, Storheia, Dyrskard, Hallingskarvet– consist of felsic metaigneous rocks with a consistent age between c.1525 and 1493 Ma. They host c.1040 Ma intrusives and c.1025 Ma Sveconorwegian metamorphism. They likely represent transported Baltican (Sveconorwegian) basement, widely exposed in S Norway. (3) The overlying nappes –Sola, Boknafjord, Kvitenut, Revseggi– are more diverse and lack counterparts in the exposed Baltican crust. The Sola nappe, near Stavanger, comprises a marine succession –Kolnes succession– of mica schist, metasandstone, marble, amphibolite and felsic metavolcanic rocks. The metavolcanic rocks –Snøda metadacite–rhyolite– are fine-grained mica gneisses, with calc-alkaline composition. Their extrusion age of c.941–934 Ma date deposition of the sequence. Detrital zircons in a metasandstone sample (n=138) yield main age modes at c.1040, 1150 and 1395 Ma, as well as significant Paleoproterozoic and Archaean modes. The Kolnes succession was affected by Taconian/Grampian metamorphism peaking in eclogite-facies conditions between c.471 and 458 Ma (Smit et al., 2010), followed by regional cooling around 445–435 Ma. Leucogranite bodies (c.429 Ma) cut the Grampian fabric. Several <sup>40</sup>Ar–<sup>39</sup>Ar white mica and biotite plateau ages constrain the timing of Scandian top-to-the SE nappe stacking at c.420 Ma. The Boknafjord nappe in Nedstrand comprises a c.932 Ma augen gneiss, overlain successively by amphibolite and mica schist units. Preliminary detrital zircon data (n=11) imply an Ordovician (<459 Ma) deposition for the mica schist. (4) The highest nappes –Karmsund and Hardangerfjord– host the Karmøy and Bømlo ophiolite complexes. These complexes comprise a c.493 Ma supra subduction zone ophiolite, intruded by c.485–466 Ma volcanic arc plutonic rocks, and unconformably overlain by fossiliferous upper Ordovician (<c.445 Ma) clastic sediments (Pedersen and Dunning, 1997).</p><p>We propose that the Iapetan Karmøy–Bømlo ophiolite complexes were accreted onto the Kolnes succession on the Laurentian side of the Iapetus realm, during the Grampian orogeny, before integration of both in the Scandian nappe pile. The age of HP metamorphism in the Kolnes succession (471–458 Ma) matches the inferred timing for obduction of the Karmøy–Bømlo complexes (485–448 Ma). The evidence for a Laurentian margin obduction stems from a conspicuous similarity with Shetland. On Shetland, the c.492 Ma Unst–Fetlar ophiolite complex was obducted during the Grampian orogeny onto Neoproterozoic Laurentian marine sequences (psammite-marble-mica gneiss) of the Westing, Yell Sound and East Mainland successions. The Westing and Yell Sound successions are characterized by a c. 944–925 Ma, Renlandian, high-grade metamorphism, a dominant detrital zircon mode at 1030 Ma, and common Archean detrital zircons. They correlate well with the Kolnes succession and suggest an ancestry along the Neoproterozoic Renlandian active margin of Laurentia and Rodinia, before opening of Iapetus. </p>

Physiological changes in soybean cultivated with soil remineralizer in the Cerrado under variable water regimes

The objective of this work was to evaluate the influence of the soil remineralizer fine-graded mica schist (FMS) on soybean (Glycine max) physiology, yield, and grain quality under different water regimes (WRs) in the Brazilian Cerrado. The experiment was conducted under field conditions for two years, using four WRs and three treatments: mica schist, conventional fertilization, and control. In 2017 and 2018, the following WRs were evaluated: WR1, WR2, WR3, and WR4, corresponding to a mean value of 100, 65, 44, and 28% of crop evapotranspiration replacement, respectively. Photosynthesis, stomatal conductance, transpiration, internal CO2 concentration, effective quantum yield of photosystem II (PSII) (Fv’/Fm’), quantum yield (PSII) (ᶲFSII), and electron transport rate reduced as a function of the advanced phenological stage of soybean and the reduction in WR. Grain quality was only affected by the WR. The mica schist was statistically similar to conventional fertilization and the control in 2017 and 2018. Yield decreased due to the anticipation of soybean phenological age and WR, but there were no differences between the three treatments in 2017 and 2018. The reduction in soybean yield is attributed to stomatal closure, loss of photoprotective capacity, and damage to the photosynthetic machinery caused by drought.