جستجوی مقالات مرتبط با کلیدواژه « ماهورا » در نشریات گروه « زمین شناسی »

The Mahura placer magnetite deposit is located in the eastern part of the Miqan Arak sedimentary basin on the border between Urmia Dokhtar and Sanandaj Sirjan structural zones in Quaternary alluvial sediments. Magnetite grains have micron to milimeter in form free grains and also inside the minerals of volcanic rocks found in the alluviums. Based on petrography and mineralogy studies, these mafic volcanic rocks are named , andesite, andesite basalt to basalt, and tiny grains of magnetite are observed inside amphibole and pyroxene mineral grains and at the border between them. According to the microprobe Analysis data of the magnetite ,, this mineral has high TiO2 and is located as a titanomagnetite or a solid solution mineral between magnetite and ilmenite, and according to the diagrams, it is placed in the group of Fe-Ti-V magnetites. The evidence obtained from the chemistry of existing clinoproxen minerals indicates that the source rock of these placers has a calc-alkaline composition and is formed in a continental arc environment , campatible with tectonic setting of Urmia Dokhtar , pressure about 2-5 kilobars and a temperature of 1100 degrees Celsius and depth between 7 to 10 km are condition to form this rocks. High content of iron-titanium, high amount of water about 10%, high fugacity of oxygen according to FMQ+1.5 system, are among the most important factors that caused immicibility and partial crystallization of magma oxide liquids and the formation of magnetite grains in the source rock of this deposit.