Genesis and Eruptive Environment of Basalts from the Shaikh-Ali Coloured Melange ,Southteast Dowlat-Abad, Baft
In direction of geological studies on existing copper mineralization in Shaikh-Aali colored melange, the study of pillow lavas of this colored melange was taken in to consideration.
Out of the most important characteristic of these pillows, the variability of diameters from 10 centimeters to more than 1.5 meters, glass skin and increasing the crystallization from margins to the center. Pillow structures show the sub oceanic eruptions in great depth which is rolled and circulated with the semi-solid stage. Mineral assemblages in this basalts including: plagioclase, pyroxene, olivine and secondary minerals are such as chlorite, calcite, epidote, quartz, opaque minerals and etc Due to the seafloor alteration (metamorphic) and also burial metamorphism alteration has taken place in the primary minerals of these basalts that which makes some changes in ratio of major oxides and minor elements (mobile elements during alteration). According to the geochemical diagrams, (major and minor elements) of investigated pillow lavas region mostly has basaltic composition and it is related to the tholeitic series, but due to seawater alteration and depilation or enrichment of some elements, some of the samples in related diagrams show the rocks out of basalt boundaries and in the determination of magmatic series they are lying between tholeitic and calc- alkaline series. The Y/Nb ratio and also minor elements diagrams show that the colored basalts of Shaikh-Aali are exactly the same as T-MORB basalts.