کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5784337 1638637 2017 51 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Iron isotopic fractionation and origin of chromitites in the paleo-Moho transition zone of the Kop ophiolite, NE Turkey
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات ژئوشیمی و پترولوژی
پیش نمایش صفحه اول مقاله
Iron isotopic fractionation and origin of chromitites in the paleo-Moho transition zone of the Kop ophiolite, NE Turkey
چکیده انگلیسی
The paleo-Moho transition zone (MTZ) of the Kop ophiolite in NE Turkey is mainly composed of dunites, which are locally interlayered with chromitites and contain minor relics of harzburgites. Large Fe isotopic variations were observed for magnesiochromite (− 0.14 to 0.06‰) and olivine (− 0.12 to 0.14‰) from the MTZ rocks. In individual samples, magnesiochromite has lighter Fe isotopic compositions than olivine, which was probably caused by subsolidus Mg-Fe exchange between them. Both magnesiochromite and olivine display an increasing trend of δ56Fe along a profile from chromitite to dunite. This trend reflects continuous fractional crystallization in a magma chamber, which resulted in heavier Fe isotopes concentrated in the evolved magmas. In each cumulate cycle of chromitite and dunite, dunite was formed from relatively evolved melts after massive precipitation of magnesiochromite. Mixing of more primitive and evolved melts in the magma chamber was a potential mechanism for triggering the crystallization of magnesiochromite, generating chromitite layers in the cumulate pile. Before mixing happened, the primitive melts had reacted with mantle harzburgites during their ascendance; whereas the evolved melts may lie on the olivine-chromite cotectic near the liquidus field of pyroxene. Variable degrees of magma mixing and differentiation are expected to generate melts with different δ56Fe values, accounting for the Fe isotopic variations of the Kop MTZ.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Lithos - Volumes 268–271, January 2017, Pages 65-75
نویسندگان
, , , , , , ,