کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4679427 1634881 2009 8 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Melting of enriched mantle beneath Pitcairn seamounts: Unusual U-Th-Ra systematics provide insights into melt extraction processes
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات علوم زمین و سیاره ای (عمومی)
پیش نمایش صفحه اول مقاله
Melting of enriched mantle beneath Pitcairn seamounts: Unusual U-Th-Ra systematics provide insights into melt extraction processes
چکیده انگلیسی
U-series systematics as well as Sr isotopes were measured on young seamount lavas from the Pitcairn hotspot collected during the Polynaut cruise. The combined U-series and Sr isotope data reveal typical mixing relationships between two endmembers. One typical 'plume' endmember with radiogenic 87Sr/86Sr and relatively low 230Th/238U and a 'lithosphere' endmember with less radiogenic 87Sr/86Sr and relatively larger 230Th/238U. Remarkably, all the lavas, except for a few arguably older samples, are characterized by 226Ra deficits relative to 230Th. On the basis of water content and trace element systematics, we argue that this is due to melting in the presence of phlogopite, which is only stable at lithosphere temperatures. A melting model including the diffusive exchange of elements among phlogopite, garnet and melt is used to constrain melting conditions of the lithosphere. These unusual 226Ra-230Th signatures can be explained by relatively slow melting rates at low matrix porosity. Our model also demonstrates that the effective partitioning behavior is dependent on the melting rate. A simple thermal model for lithosphere heating and melting is in good agreement with predicted melting rates.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Earth and Planetary Science Letters - Volume 277, Issues 3–4, 30 January 2009, Pages 474-481
نویسندگان
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