Coupled Microfracturing and Chemical Weathering of Precambrian Quartzite in the Extremely Humid and Tectonically Active Shillong Plateau, NE India: Implications for In Situ Quartz Weathering and Quartz Silt Production

2020 ◽  
Vol 128 (2) ◽  
pp. 201-226
Author(s):  
Sarajit Sensarma ◽  
R. V. S. Shimyaphy ◽  
Tapan Chakraborty
Keyword(s):  
Chemical Weathering ◽  
Shillong Plateau ◽  
Ne India ◽  
Tectonically Active

Dating of chemical weathering processes by in situ measurement of U-series disequilibria in supergene Fe-oxy/hydroxides using LA-MC-ICPMS

2006 ◽  
Vol 235 (1-2) ◽  
pp. 76-94 ◽  
Author(s):  
J.P. Bernal ◽  
S.M. Eggins ◽  
M.T. McCulloch ◽  
R. Grün ◽  
R.A. Eggleton
Keyword(s):  
Chemical Weathering ◽  
In Situ Measurement ◽  
Weathering Processes

Patchy bedrock explained: Tectonic fracture control on landscape evolution patterns in south-Central Chile 

2021 ◽  
Author(s):  
Emma Lodes ◽  
Dirk Scherler ◽  
Hella Wittmann ◽  
Renee Van Dongen
Keyword(s):  
Chemical Weathering ◽  
Landscape Evolution ◽  
Tectonic Deformation ◽  
Fracture Density ◽  
Rock Fracturing ◽  
Central Chile ◽  
Erosion Rates ◽  
Denudation Rates ◽  
South Central

<p>Rock fracturing induced by tectonic deformation is thought to promote faster denudation in more highly fractured areas by lowering grain size and directing the flow of water. That the density and pattern of fractures in a landscape play a role in controlling erosion and landscape evolution has been known for over a century, but not until recently do we have tools, like cosmogenic nuclides, to quantify erosion rates in places with varying fracture densities. In the Nahuelbuta Range in south-central Chile, we observed that >30-m thick regolith exists next to patches of unweathered bedrock. We hypothesize that the density of fractures dictates the pace and patterns of chemical weathering, regolith conversion, and erosion in the Nahuelbuta Range. To test this, we used in situ cosmogenic <sup>10</sup>Be to obtain denudation rates from amalgamated samples of bedrock, corestones and soils, and measured fracture density and orientation, as well as hillslope boulder size in several sites in the Nahuelbuta Range. We found that more highly fractured areas indeed have higher denudation rates than less fractured areas, and that bedrock denudation rates are ~10 m/Myr while soil denudation rates are ~30 m/Myr, suggesting that soil-covered areas may be sites of higher fracture density at depth. Fractures have orientations that match mapped faults across the Nahuelbuta range, and thus are considered to be tectonically-induced. In addition, both fracture and fault orientations match the orientation of streams incising the range, suggesting that fractures control stream channel orientation by weakening bedrock and thus directing flow.</p>

scholarly journals Localization and Surface Characterization by Zhurong Mars Rover at Utopia Planitia

2021 ◽  
Author(s):  
Liang Ding ◽  
Ruyi Zhou ◽  
Tianyi Yu ◽  
Haibo Gao ◽  
Huaiguang Yang ◽  
...  
Keyword(s):  
Surface Characterization ◽  
Chemical Weathering ◽  
Friction Angle ◽  
Parameter Analysis ◽  
Mars Rover ◽  
Slip Ratio ◽  
Physical Weathering ◽  
Weathering Processes ◽  
Primary Localization

Abstract China’s first Mars rover, Zhurong, has successfully touched down on the southern Utopia Planitia of Mars at 109.925° E, 25.066° N, and since performed cooperative multiscale investigations with the Tianwen-1 orbiter. Here we present primary localization and surface characterization results based on complementary data of the first 60 sols. The Zhurong rover has traversed 450.9 m southwards over a flat surface with mild wheel slippage (less than 0.2 in slip ratio). The encountered crescent-shaped sand dune indicates a NE-SW local wind direction, consistent with larger-range remote-sensing observations. Soil parameter analysis based on terramechanics indicates that the topsoil has high bearing strength and cohesion, and its equivalent stiffness and internal friction angle are ~1390-5872 kPa∙m-n and ~21°-34° respectively. Rocks observed strewn with dense pits, or showing layered and flaky structures, are presumed to be involved in physical weathering like severe wind erosion and potential chemical weathering processes. These preliminary observations suggest great potential of in-situ investigations by the scientific payload suite of the Zhurong rover in obtaining new clues of the region’s aeolian and aqueous history. Cooperative investigations using the related payloads on both the rover and the obiter could peek into the habitability evolution of the northern lowlands on Mars.

scholarly journals Evaluation of the Influence of In Situ Stress on the Stability of Mine Pit Walls: A Case Study of Songwe Mine

2021 ◽  
Vol 4 (2) ◽  
pp. p1
Author(s):  
Dyson Moses ◽  
Hideki Shimada ◽  
Takashi Sasaoka ◽  
Akihiro Hamanaka ◽  
Tumelo K. M Dintwe ◽  
...  
Keyword(s):  
Active Regions ◽  
Horizontal Stress ◽  
In Situ Stress ◽  
Slope Instability ◽  
Open Pit ◽  
Stress Regime ◽  
Tectonically Active ◽  
The Stability ◽  
The Impact

The investigation of the influence of in situ stress in Open Pit Mine (OPM) projects has not been accorded a deserved attention despite being a fundamental concern in the design of underground excavations. Hence, its long-term potential adverse impacts on pit slope performance are overly undermined. Nevertheless, in mines located in tectonically active settings with a potential high horizontal stress regime like the Songwe mine, the impact could be considerable. Thus, Using FLAC3D 5.0 software, based on Finite Difference Method (FDM) code, we assessed the role of stress regimes as a potential triggering factor for slope instability in Songwe mine. The results of the evaluated shearing contours and quantified strain rate and displacement values reveal that high horizontal stress can reduce the stability performance of the pit-wall in spite of the minimal change in Factor of Safety (FoS). Since mining projects have a long life span, it would be recommendable to consider “in situ stress-stability analyses” for OPM operations that would be planned to extend to greater depths and those located in tectonically active regions.

scholarly journals Direct measurement of fungal contribution to silicate weathering rates in soil

Geology ◽  
2021 ◽  
Author(s):  
Bastien Wild ◽  
Gwenaël Imfeld ◽  
Damien Daval
Keyword(s):  
Chemical Weathering ◽  
Silicate Weathering ◽  
Nutrient Fluxes ◽  
Weathering Rates ◽  
Relative Contribution ◽  
Quantitative Estimates ◽  
Fungal Hyphae ◽  
Nanoscale Topography ◽  
Natural Settings

Chemical weathering produces solutes that control groundwater chemistry and supply ecosystems with essential nutrients. Although microbial activity influences silicate weathering rates and associated nutrient fluxes, its relative contribution to silicate weathering in natural settings remains largely unknown. We provide the first quantitative estimates of in situ silicate weathering rates that account for microbially induced dissolution and identify microbial actors associated with weathering. Nanoscale topography measurements showed that fungi colonizing olivine [(Mg,Fe)2SiO4] samples in a Mg-deficient forest soil accounted for up to 16% of the weathering flux after 9 mo of incubation. A local increase in olivine weathering rate was measured and attributed to fungal hyphae of Verticillium sp. Altogether, this approach provides quantitative parameters of bioweathering (i.e., rates and actors) and opens new avenues to improve elemental budgets in natural settings.

scholarly journals In Situ Stress and Stress Regime in the Onshore Part of the Northeast Java Basin

2021 ◽  
Vol 44 (2) ◽  
pp. 95-105
Author(s):  
Agus M. Ramdhan
Keyword(s):  
Petroleum Industry ◽  
Horizontal Stress ◽  
In Situ Stress ◽  
Vertical Stress ◽  
Stress Regime ◽  
Severe Erosion ◽  
Tectonically Active ◽  
Minimum Horizontal Stress ◽  
Maximum Horizontal Stress

In situ stress is importance in the petroleum industry because it will significantly enhance our understanding of present-day deformation in a sedimentary basin. The Northeast Java Basin is an example of a tectonically active basin in Indonesia. However, the in situ stress in this basin is still little known. This study attempts to analyze the regional in situ stress (i.e., vertical stress, minimum and maximum horizontal stresses) magnitude and orientation, and stress regime in the onshore part of the Northeast Java Basin based on twelve wells data, consist of density log, direct/indirect pressure test, and leak-off test (LOT) data. The magnitude of vertical (  and minimum horizontal (  stresses were determined using density log and LOT data, respectively. Meanwhile, the orientation of maximum horizontal stress  (  was determined using image log data, while its magnitude was determined based on pore pressure, mudweight, and the vertical and minimum horizontal stresses. The stress regime was simply analyzed based on the magnitude of in situ stress using Anderson’s faulting theory. The results show that the vertical stress ( ) in wells that experienced less erosion can be determined using the following equation: , where  is in psi, and z is in ft. However, wells that experienced severe erosion have vertical stress gradients higher than one psi/ft ( . The minimum horizontal stress ( ) in the hydrostatic zone can be estimated as, while in the overpressured zone, . The maximum horizontal stress ( ) in the shallow and deep hydrostatic zones can be estimated using equations: and , respectively. While in the overpressured zone, . The orientation of  is ~NE-SW, with a strike-slip faulting stress regime.

scholarly journals Datation de surfaces geomorphologiques reperes par le 10 Be produit in-situ; implications tectoniques et climatiques

2001 ◽  
Vol 172 (2) ◽  
pp. 223-236 ◽  
Author(s):  
Lionel L. Siame ◽  
Regis Braucher ◽  
Didier L. Bourles ◽  
Olivier Bellier ◽  
Michel Sebrier
Keyword(s):  
Cosmic Rays ◽  
Nuclear Physics ◽  
Active Faults ◽  
Active Regions ◽  
Cosmic Ray ◽  
Tectonic Activity ◽  
Slip Rates ◽  
Tectonically Active ◽  
The Impact

Abstract The evolution of continental landforms is mainly modulated by the impact of climatic and tectonic processes. Because of their distinctive morphology and the periodicity of their deposition, climatically induced landforms such as alluvial fans or terraces are well suited to infer rates of tectonic and continental climatic processes. Within tectonically active regions, an important step consists in dating displaced geomorphic features to calculate slip rates on active faults. Dating is probably the most critical tool because it is generally much more simpler to measure deformation resulting from tectonic activity than it is to accurately date when that deformation occurred. Recent advances in analytical chemistry and nuclear physics (accelerator mass spectrometry) now allow quantitative abundance measurements of the extremely rare isotopes produced by the interaction of cosmic rays with surface rocks and soils, the so-called in situ-produced cosmogenic nuclides ( 3 He, 10 Be, 21 Ne, 26 Al, 36 Cl), and allow to directly date the duration that a landform has been exposed to cosmic rays at the Earth's surface [Lal, 1991; Nishiizumi et al., 1993; Cerling and Craig, 1994; Clark et al., 1995]. In fact, the abundance of these cosmonuclides is proportional to landscape stability and, under favorable circumstances, their abundance within surface rocks can be used as a proxy for erosion rate or exposure age. These cosmonuclides thus provide geomorphologists with the opportunity to constrain rates of landscape evolution. This paper presents a new approach that combines cosmic ray exposure (CRE) dating using in situ-produced 10 Be and geomorphic as well as structural analyses. This approach has been applied on two active strike-slip and reverse faults located in the Andean foreland of western Argentina. These two case studies illustrate how CRE dating using in situ-produced 10 Be is particularly well suited for geomorphic studies that aim to estimate the respective control of climate and tectonics on morphogenesis.

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