Mineralogy and Geochemistry of Nephrite from Wolay Deposited, Kunar, East Afghanistan
This research deals with the study of geochemical, petrographic and mineralogical properties of Wolay Nephrite Occurrences in Kunar Province. Nephrite is a relatively silicate mineral, Cyclosilicate, with a chemical composition of Ca2(Mg,Fe)5Si8O22(OH)2 and has a monocline crystal shape. It is found in metamorphic rocks in many parts of the world. Wolay nephrite area is related to the tectonic zone of Jalalabad. Jalalabad zone is located in the eastern part of Afghanistan and south-east of the Nuristan zone. Correspondingly, this zone is related to the upper Cambrian or younger Cambrian. In this area, the age of rocks is related to Archean- Middle Proterozoic AR-PR2. This contribution presents the first systematic mineralogical and geochemical studies on the Wolay nephrite deposit. Electron probe microanalysis, X-ray fluorescence (XRF) spectrometry, inductively coupled plasma mass spectrometry (ICP-MS), and isotope ratio mass spectrometry was used to measure the mineralogy, bulk-rock chemistry, and stable (O and H) isotopes characteristics of samples from Kunar. Field investigation shows that the Kunar nephrite ore body occurs in the dolomitic marble near the intruding granitoids. Petrographic studies indicate that the nephrite is mainly composed of fine-grained actinolite with Schist and dolomite. Geochemical studies show that all nephrite samples have low bulk-rock Fe/(FeO + MgO) values (4.72–21.34%), as well as SiO2 (72.75%), Al2O3 (2.01), CaO (14.58%) and NiO (0.05%) contents. The chemical data analysis and interpretation of F=Mg/Mg+Fe percentages show that the Nephrites type is actinolite. The deposit of nephrite mineral has been formed in hydrothermally veins and lens shape in contact with serpentinite and carbonate (dolomite marble) rock in the under study area. The color and its clarity have a direct effect on the economy and its price. The Nephrite from the Khas Konur district is found in green color due to the existence of iron elements.