کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
8911622 | 1638619 | 2018 | 36 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Oxygen isotope and trace element compositions of platiniferous dunite pipes of the Bushveld Complex, South Africa - Signals from a recycled mantle component?
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
علوم زمین و سیارات
ژئوشیمی و پترولوژی
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چکیده انگلیسی
Platiniferous dunite pipes occur in the lower mafic/ultramafic portion of the Rustenburg Layered Suite of the Bushveld large igneous province (LIP). Olivine compositions in these pipes range from forsterite (Fo) 80 to 35â¯mol% and suggest crystallization from variably evolved magmas at high temperatures (~1200â¯Â°C). The most primitive olivines are from a stock unit and have the highest contents of Ni (>0.15â¯wt%) and lowest contents of Mn (<0.3â¯wt%). Fractional crystallization and partial melting of pyroxenite host rock play a significant role in the formation of the fayalitic olivines with its high Mn contents (>0.3â¯wt%). High δ18O values of olivine (5.7-7.0â°) and pyroxene (6.7-7.4â°) are akin to those of the Lower and Critical Zone of the Bushveld intrusion suggesting a common origin. The constant high O isotope ratios with variable Fo contents in the olivines are unlike trends observed in olivine phenocrysts in magmas forming by assimilation-fractional crystallization. We suggest that the high δ18O in the most primitive dunites reflect that of the primary melt of the Bushveld pipes, indicating either a bulk assimilation of crust prior to pipe formation or a contribution from recycled oceanic crust in the sub-continental lithospheric mantle (SCLM). The latter scenario is supported by the high Ni/Mn ratios in primitive pipe olivine that might be inherited from melting of a pyroxene-rich mantle source.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Lithos - Volumes 310â311, June 2018, Pages 332-341
Journal: Lithos - Volumes 310â311, June 2018, Pages 332-341
نویسندگان
T. Günther, K.M. Haase, M. Junge, T. Oberthür, D. Woelki, S. Krumm,