Petrography, Temperature Measurement, and Economic Evaluation of Granitoid Pluton of Qohrud-Kashan Using EPMA, XRD, and XRF Analysis

Abstract

The area which is being studied is located in northwest of Isfahan, 30 kilometers south of Kashan, and southern section of Qmasar. The longitude of the area of study is 51°19'13"E to 51°26'26"E and its latitude is 33°34'24"N to 33°44'24"N. Based on microscopic observations, modal analysis, and also based on their location in the Streckeisen [QAPF], both the stones of the Qohrud batholitic mass themselves and its enclaves are more in quartz monzonite ranges. Granitoid also have quartz monzonite enclaves. These enclaves are from both microgranular mafic and Autolith types which indicate the mixing of two magmas. At the center of the pluton, there are indications of existence of main magma reservoir and magma mixing. In terms of mineralogy, the granitoid rocks of the area very much resemble I-type. The zoning of the plagioclases is both the normal kind and variation invert and has andesine general composition. The probed biotite sample contains iron and belongs to a granitic sample from the center of the mass. Also, the ranking graph indicates biotite as the source of recrystallization for the analyzed points. The probed biotite sample of the Qohrud area showed formation temperature of 730 degrees centigrade. According to the Rb and Sr contents, the source of the rocks is at depths of 20 to 30 kilometers from the earth’s surface that are depending on the subduction zone. The formation temperature of the specimens of the Qohrud batholithic mass is mostly between 900 to 1000 degrees centigrade. [At] the center of the mass (around Qahrud), the amount of molybdenum is higher than the economic limit.