https://scholars.lib.ntu.edu.tw/handle/123456789/633316
標題: | Mineral chemistry, Thermobarometry, Geochemistry and tectonic setting of Tertiary andesitic lavas in the Shourestan area (west of Sarbisheh), Southern Khorasan | 作者: | Mohammadi, Seyyed Saeid SUN-LIN CHUNG Nakhaei, Malihe Islamipanah, Arash |
關鍵字: | active continental margin | lithospheric mantle | Lut | Pyroxene andesite | Shourestan | spinel lherzolite | thermobarometry | 公開日期: | 1-一月-2022 | 卷: | 14 | 期: | 4 | 起(迄)頁: | 175 | 來源出版物: | Journal of Economic Geology | 摘要: | In the Shourestan area, 14 kilometers west of Sarbisheh city, in South Khorasan province, volcanic rocks with pyroxene-andesite composition belonging to Eocene-Oligocene are exposed. The constituent minerals of these rocks include plagioclase and pyroxene. The composition of plagioclases have range from Ab32, An68 to Ab58, An42 and are andesine-labradorite type. Clinopyroxene and orthopyroxene have diopside-like augite and enstatite composition, respectively. The crystallization temperature for clinopyroxene and orthopyroxene were about 1175 and 1200 °C respectively and the pressure (for both types) was 2 to 5 kb. The geochemical data of whole rocks show that the andesitic lavas of Shourestan have high potassium calc-alkaline nature and the amount of Mg# in them varies from 40.97 to 60.97, which indicates the role of mantle components in their formation. These rocks show signs of differentiation including LREE/HREE ((La/Yb)N) between 9.95 to 12.42, LREE/MREE ((La/Sm)N) between 3.53 to 6.55, MREE/HREE ((Sm/Yb)N) between 1.89 to 2.99. High ratios of Zr/Nb (9.81-22.10), Th/Nb (0.68-1.79), Th/Ta (7.29-24), and Nb/Ta (9.69-15.66) along with the pattern of LIL elements, support the possibility of different degrees of crustal contamination-assimilation of magma during its ascent to the earth's surface. The studied rocks have low ratios of Ce/Y (2.44-3.48), (Tb/Yb)N (1.17-1.39), Sm/Yb (1.92-2.78), and relatively flat MREE-HREE pattern that confirms the melting of the subcontinental lithospheric mantle in the field of spinel stability and at a depth of fewer than 75 kilometers. |
URI: | https://scholars.lib.ntu.edu.tw/handle/123456789/633316 | ISSN: | 20087306 | DOI: | 10.22067/econg.2023.80746.1065 |
顯示於: | 地質科學系 |
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