ترکیب شیمیایی کانی ها و پیدایش برونبومهای ریزدانه مافیکی در سنگهای پلوتونیکی حد واسط - اسیدی منطقه کوه زر در جنوب - شرقی سمنان

The Kub-e- Zar area is located about 75 Km in southeast of Semnan. Electron microprobe analyses of plagioclases of mafic microgranular enclaves and plutonic host rocks from Kuh-e-Zar area display that they have normal, oscillatory and reverse zoning, so that plagioclase cores of reverse zoning in enclaves have oligoclase and andesine compositions and their rims have andesine and laboradorite compositions, respectively. Investigation of biotite compositions in host rocks show that in the host granodiorite rocks, there are two types of biotites. The first type has high Ti02 (mean 4.8%), Alz03 mean 12.84%), MgO (meanI5.38%) and low Si02 (36.89%), which are similar to mafic microgranular enclaves (mean Ti02 4.67%, Alz03 13.03%, MgO 15.19% and Si02 37.23%). the second type is depleted in Ti02 (mean 0.04%) and MgO (mean 0.02%) and enriched in Al20 3 (mean 18.09%) and Si02 (mean 64.5%). Contents of these elements in the biotites of host monzodiorite rocks are similar to enclaves. Chemical compositions of pyroxenes in enclaves are similar in compositions to those of host rocks. These features, in addition to the patterns and aboundances of trace elements in enclaves, the presence of inclusions of fine grain biotite and hornblende in feldspares, synplutonic dykes, the nature of the plagioclase zoning and etc. display magma mixing and mingling origin for generation of these enclaves.