Aynak is the largest known copper deposit in Afghanistan, with indicated resources of 240 Mt grading 2.3% Cu placing it in the 'giant' category. Host rocks are Neoproterozoic metasediments comprising dolomitic marble, carbonaceous quartz schist and quartz-biotite-dolomite schist containing garnet, scapolite and apatite. Chalcopyrite and bornite dominate the hypogene ore with lesser pyrite, pyrrhotite, cobaltite and chalcocite, and rare sphalerite, molybdenite, uraninite and barite. Sulphides occur as bedding-parallel laminae, disseminations, metamorphic segregations and crosscutting veins. Sulphide δ34S ratios range –14.5 to +17.3‰ in bedded and disseminated sulphides (n = 34). This broad range favours biogenic reduction of seawater sulphate as a major source of sulphur, although thermochemical reduction processes are not precluded. The narrower δ34S range of –6 to +12.2‰ in vein and segregation sulphides (n = 21) suggests localized redistribution and partial homogenization during metamorphism. Geochemical associations suggest that Al, P, Ca, Ti and Fe were primary sedimentary constituents whereas Cu, Mg, S, Se, As, Co and Bi were introduced subsequently. We infer that Aynak originated as a shale- and carbonate-hosted stratabound replacement deposit, resembling orebodies of the Central African Copperbelt, although underlying red-beds are absent at Aynak and mafic volcanics were the probable copper source. These giant deposits formed worldwide in the Cryogenian probably due to marine enrichment in copper, magnesium and sulphate coincident with profuse basaltic volcanism and ocean oxidation.
On June 21th, a Mw6.2 earthquake struck the Afghan-Pakistan-border-region, an area dominated by partitioned deformation related to the India-Asia collision. Despite its moderate size, 1150 deaths were reported, making the event the deadliest earthquake of 2022 so far. We investigate the event’s rupture processes, aiming to understand what made it that fatal. Our InSAR-constrained slip model and regional moment-tensor inversion reveal a sinistral rupture with maximum slip of 1.8 m at 5 km depth on a N20°E striking, sub-vertical fault. Field observations confirm fault location and slip-sense. Based on our analysis and a global comparison, we suggest that not only external factors (e.g. time of the event and building stock) but also fault-specific factors made the event excessively destructive. Surface rupture was favored by the local rock anisotropy (foliation), coinciding with the fault strike. The distribution of Peak Ground Velocity was governed by the sub-vertical fault. The maximum slip was large compared to other events globally and might have resulted in peak-frequencies coinciding with the resonance-frequency of the local one-story buildings. More generally, our study demonstrates the devastating impact of moderate earthquakes, being small enough to be accommodated by many tectonic structures but large enough to cause significant damage.
Abstract On June 21st, a Mw6.2 earthquake struck the Afghan‐Pakistan‐border‐region, situated within the India‐Asia collision. Thousand thirty‐nine deaths were reported, making the earthquake the deadliest of 2022. We investigate the event's rupture processes by combining seismological and geodetic observations, aiming to understand what made it that fatal. Our Interferometric Synthetic Aperture Radar‐constrained slip‐model and regional moment‐tensor inversion, confirmed through field observations, reveal a sinistral rupture with maximum slip of 1.8 m at 5 km depth on a N20°E striking, sub‐vertical fault. We suggest that not only external factors (event‐time, building stock) but fault‐specific factors made the event excessively destructive. Surface rupture was favored by the rock foliation, coinciding with the fault strike. The distribution of Peak‐Ground‐Velocity was governed by the sub‐vertical fault. Maximum slip was large compared to other events globally and might have resulted in peak‐frequencies coinciding with resonance‐frequencies of the local buildings and demonstrates the devastating impact of moderate‐size earthquakes.
Abstract On June 21th, a Mw6.2 earthquake struck the Afghan-Pakistan-border-region, an area dominated by partitioned deformation related to the India-Asia collision. Despite its moderate size, 1150 deaths were reported, making the event the deadliest earthquake of 2022 so far. We investigate the event’s rupture processes, aiming to understand what made it that fatal. Our InSAR-constrained slip model and regional moment-tensor inversion reveal a sinistral rupture with maximum slip of 1.8 m at 5 km depth on a N20°E striking, sub-vertical fault. Field observations confirm fault location and slip-sense. Based on our analysis and a global comparison, we suggest that not only external factors (e.g. time of the event and building stock) but also fault-specific factors made the event excessively destructive. Surface rupture was favored by the local rock anisotropy (foliation), coinciding with the fault strike. The distribution of Peak Ground Velocity was governed by the sub-vertical fault. The maximum slip was large compared to other events globally and might have resulted in peak-frequencies coinciding with the resonance-frequency of the local one-story buildings. More generally, our study demonstrates the devastating impact of moderate earthquakes, being small enough to be accommodated by many tectonic structures but large enough to cause significant damage.
Afghanistan comprises a collage of many lithotectonic domains sutured together as block terranes on the southern Eurasian Plate by collisional tectonics throughout the Proterozoic and Phanerozoic. Kabul basement rocks are fragments of an Archaean block stabilized in early Precambrian with two later metamorphic events correlating well with global-scale orogenies related to assembly of the Paleoproterozoic Columbia and Neoproterozoic Rodinia supercontinents. These collisional tectonics were followed by igneous episodes and production of multiple ophiolite suites divided into three orogenic episodes of the later Palaeozoic (Devonian – Permian) Variscan (Hercynian) Orogeny, the Mesozoic (Triassic – Early Cretaceous) Cimmerian Orogeny, and the dominantly Cenozoic (Late Cretaceous – Quaternary) Himalayan (Alpine) Orogeny. Variscan, Cimmerian, and Himalayan accreted blocks are separated by prominent suture and fault zones, several of which are active and a source of considerable seismic hazard, especially in eastern Afghanistan. This resulting mélange of small exotic blocks was brought about by a rifting series of narrow ribbon terranes from the Gondwana coast of the Paleotethys and Neotethys seaways. Recent revival of Afghan-led geological lithologic and geochemical assessments has led to new interpretations of tectonic history, as well as of vital surface and groundwater, and other natural resources. Recurrent droughts have decreased water supplies, which have undergone extensive contamination, along with uncontrolled over-pumping of aquifers. Increasing attention to the rich mineral resource base in the country offers solutions to chronic budgetary shortfalls.
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