The Exploration of Metallic Deposits Using Satellite Image Processing in the Parwan-Panjsher Area, Afghanistan

Unique tectonic features have resulted in diverse metallic and non-metallic mineralization in Afghanistan. Hence, this paper is focused on the development of exploration and mineral resource data in Afghanistan. The study area is located in the western Hindu Kush tract and on the northern verge of the Hari Rud–Panjsher fault, Afghanistan, which mainly associates with the western Hindu Kush and Badakhshan plutonic belts. The rock units include crystalline limestones and diabase formed during the Paleozoic era and Triassic period. The aim of this study was to employ Remote Sensing (RS) methods by using the Landsat-8 satellite and ASTER sensor to spot iron and copper mineralization zones in the Parwan-Panjsher area. Therefore, Band Composition, Principal Component Analysis (PCA), and Band Ratio were applied to identify the iron oxide minerals. The detected area provided by satellite images had very good conformability with the results of field studies. Furthermore, mineralization of carbonate host-rock iron and Fe–Cu–(Au) skarn were observed during the field surveys. Hematite–Magnetite, Chalcopyrite, and pyrite mineralization have resulted from the injection of various diabase subvolcanic into carbonate units. Additionally, high heat flow has caused widespread marble formation in the area. The results were supported by microscopic and geochemical studies.

Bat guano minerals and mineralization processes in Chameau Cave, Eastern Morocco

The decay of bat guano deposits in caves produces mineral accumulations, mainly phosphates and secondary sulfates. Chameau Cave, Eastern Morocco, is located in the semi-arid Bni Snassen Mountains. It is composed of semi-active and dry passages, and is featured by strong condensation-corrosion on the walls, presence of fluvial sediments, and old corroded flowstones. Due to forced and convective airflow, the cave is generally very dry, with some damp sites related to condensation. Samples collected on the surface of different passages and along two sediment profiles yielded minerals related to bat guano decay. On recent or fresh guano, precursor minerals correspond to sulfate (gypsum), phosphate-sulfate (ardealite) and phosphate (brushite). Phosphates (hydroxylapatite, fluorapatite) occur at the interface with host rock or carbonate speleothems. At the contact of phyllosilicates contained in allogenic fluvial deposits or shale partings, or with pyrite-rich sediments, various phosphates occur (Al-rich strengite, Fe-rich variscite, phosphosiderite, leucophosphite, spheniscidite, crandallite, minyulite, variscite, and strengite), the latter two minerals being the stable end-members. Black seams of oxyhydroxides (goethite, hematite, birnessite) line the contact between carbonate host rock and weathered fluvial deposits. After “digestion” by acidic guano leachates, fluvial deposits only display the most resistant minerals (quartz, muscovite, K-feldspars and Na-plagioclases) and weathering byproducts (kaolinite). We discuss the origin of a pure gypsum particle cone, possibly related to evaporation at the edge of a wet cupola and subsequent detachment of sulfate particles. Among environmental conditions, humidity is required for decay. In this dry cave, most of the damp originates from either permanent or seasonal condensation. Dust particle advection seems to be essential in providing compounds that are not present on fresh guano (quartz, clay minerals). Bat guano phosphatization has probably occurred since >100 ka. The Chameau Cave appears as an outstanding site for bat guano-related minerals (n = 12), including rare phosphates (spheniscidite and minyulite).

Polished slickensides preserved in the Obir Caves (Austria) close to the Periadriatic Fault System

<p>We studied polished slickensides, which are perfectly preserved in the Obir Caves (Northern Karavanke Mountains, Austria) situated in the Middle Triassic Wetterstein limestone of the Hochobir massif. The investigated area is located close to the seismogenic ESE-trending Periadriatic Fault System, which is the border between the Eastern and Southern Alps. The polished slickensides observed on a block between two major left-lateral NE-SW trending slickensides record a range of polishing from none to highly-reflective fault surfaces. A classification of the different polishing grades of the fault surfaces inside the cave compared with their spatial orientation shows that there is no relationship between the degree of polishing and fault orientation. Associated cataclastically deformed brittle fault zones and partly polished slickensides at the cave entrance and on the Eastern slope of the Hochobir massif where the fault zone localizes in shattered dolomitic rocks, show similar kinematics and spatial orientation to the faults inside the Obir Caves.</p><p>Thin section analysis identified the smooth fault mirror surfaces as principal slip surfaces. Cataclastic grains are truncated along the principal slip surfaces and along secondary Riedel faults. Five different stages of cataclastic deformation can be distinguished: I) Undeformed carbonate host rock. II) Isolated fractures in the host rock with injected ultracataclastic material. III) Dilation cataclasites containing jigsaw breccia. IV) Ultracataclasite with angular-to-rounded host rock fragments and jigsaw breccia. V) Ultracataclasite with isolated clasts and truncated grains close to the mirror surfaces.</p><p>The microstructures including polished slickensides, injected cataclasites and truncated grains along principal slip surfaces as well as the geological position close to the seismogenic Periadriatic Fault System suggest that the investigated fault surfaces in the Obir Caves formed during seismic slip.</p>

Understanding the deglacial relationship between carbon isotopes and temperature in stalagmites from Western Europe

<p>The last deglaciation was a period of rapid and profound climatic change in Western Europe. Speleothem carbon isotope (δ<sup>13</sup>C) records from mid-latitude Western Europe have consistently shown large and reproducible excursions over this time period, strikingly similar to available temperature reconstructions from other archives. The mechanism behind the temperature sensitivity of speleothem δ<sup>13</sup>C, however, remains poorly constrained, due to the complex interplay of multiple processes affecting this proxy.</p><p>Here we use a multi-proxy approach and forward modelling of karst processes to investigate what drives the response of speleothem δ<sup>13</sup>C to the last deglaciation in Western Europe. We present new proxy data (<sup>14</sup>C and δ<sup>44</sup>Ca) from speleothem Candela from El Pindal Cave, northern Spain, which covers the period from the Last Glacial Maximum (25 ka BP) to the Early Holocene (8 ka BP). Previously published stable isotope data (Moreno et al., 2010) revealed a pronounced decrease in δ<sup>13</sup>C over the deglaciation (~8‰ VPDB) which closely tracks regional temperature records from the Iberian Margin. We make use of the different sensitivities of ancillary proxies (<sup>14</sup>C, Mg/Ca, and δ<sup>44</sup>Ca) to processes in soil and karst to quantify their relative importance on the δ<sup>13</sup>C shift. For this, we use the forward modelling software CaveCalc (Owen et al., 2018) to generate a large ensemble of possible solutions, from which the ones closest matching the data are chosen and evaluated.</p><p>Our preliminary results suggest that in-cave and karst processes (carbonate host rock dissolution and reprecipitation) cannot explain the full amplitude of the δ<sup>13</sup>C shift over the deglaciation, and that changes in soil δ<sup>13</sup>C are to some extent translated to the speleothem carbonate δ<sup>13</sup>C. The possibility of quantitatively disentangling processes in the soil from other karst processes could allow the reconstruction of past soil activity from speleothems.</p><p> </p><p>References:</p><p>Moreno, A., Stoll, H., Jiménez-Sánchez, M., Cacho, I., Valero-Garcés, B., Ito, E., Edwards, R.L., 2010. A speleothem record of glacial (25-11.6 kyr BP) rapid climatic changes from northern Iberian Peninsula. Glob. Planet. Change 71, 218–231. doi:10.1016/j.gloplacha.2009.10.002</p><p>Owen, R.A., Day, C.C., Henderson, G.M., 2018. CaveCalc: A new model for speleothem chemistry & isotopes. Comput. Geosci. doi:10.1016/J.CAGEO.2018.06.011</p>

Ferroan Dolomitization by Seawater Interaction with Mafic Igneous Dikes and Carbonate Host Rock at the Latemar Platform, Dolomites, Italy: Numerical Modeling of Spatial, Temporal, and Temperature Data

Numerous publications address the petrogenesis of the partially dolomitized Latemar carbonate platform, Italy. A common factor is interpretation of geochemical data in terms of heating via regional igneous activity that provided kinetically favorable conditions for replacement dolomitization. New field, petrographic, XRD, and geochemical data demonstrate a spatial, temporal, and geochemical link between replacement dolomite and local mafic igneous dikes that pervasively intrude the platform. Dikes are dominated by strongly altered plagioclase and clinopyroxene. Significantly, where ferroan dolomite is present, it borders dikes. We hypothesize that seawater interacted with mafic minerals, causing Fe enrichment in the fluid that subsequently participated in dolomitization. This hypothesis was tested numerically through thermodynamic (MELTS, Arxim-GEM) and reactive flow (Arxim-LMA) simulations. Results confirm that seawater becomes Fe-enriched during interaction with clinopyroxene (diopside-hedenbergite) and plagioclase (anorthite-albite-orthoclase) solid solutions. Reaction of modified seawater with limestone causes ferroan and nonferroan replacement dolomitization. Dolomite quantities are strongly influenced by temperature. At 40 to 80°C, ferroan dolomite proportions decrease with increasing temperature, indicating that Latemar dolomitization likely occurred at lower temperatures. This relationship between igneous dikes and dolomitization may have general significance due to the widespread association of carbonates with rifting-related igneous environments.

Diagenesis, regular growth and records of seasonality in inoceramid bivalve shells from mid-Maastrichtian hemipelagic beds of the Bay of Biscay

Inoceramid bivalve shells from outcrops of mid-Maastrichtian deep-water carbonate, hemipelagic beds in the Bay of Biscay exhibit post-depositional diagenetic alteration. New data from isotopic analysis (carbon and oxygen), together with observations of the inoceramid shells and carbonate host-rock using cathodoluminescence (CL) and scanning electron microscopy (SEM), confirm a lateral, westerly increase in the degree of diagenesis, without any substantial textural changes in the alternating dark and clear growth lines of the shell microstructure. Under CL, a bright yellowish to red colour is observed in the most diagenetically altered inoceramid samples. Non-luminescent areas are restricted to the central parts of the less altered shells. A detailed geochemical analysis by electron microprobe, along intrashell profiles of the non-luminescent and luminescent zones has revealed that Mg/Ca, Sr/Ca, Na/Ca, Fe/Ca and Mn/Ca ratios show oscillatory curves but behave differently. Fe/Ca, Mn/Ca and Na/Ca ratios are well correlated but usually show an opposite relationship when compared with the Mg/Ca and Sr/Ca ratios of both luminescent and non-luminescent shell areas. Our findings have palaeoenvironmental implications in that the geochemistry of the regular, alternating dark and clear growth lines seems to be related to the input of seasonally controlled phytodetritus to the basin floor.