K-rich glass-bearing wehrlite xenoliths from Yitong, Northeastern China: petrological and chemical evidence for mantle metasomatism

Melting temperatures of the assemblage pyroxene + garnet on the enstatite‐pyrope join were experimentally determined at 11 different pressures between 80 and 152 kbar with a split‐sphere anvil apparatus (USSA‐2000). The compositions of pyroxene, garnet, and melt coexisting along the solidus were also determined. Comparison with previous data at lower temperatures revealed a large temperature dependence of the compositions of garnet coexisting with pyroxene. It is proposed that the observed variation in the garnet composition is caused by disorder in garnet. The obtained alumina contents of orthopyroxene coexisting with garnet on the solidus at 80–110 kbar contributed to an improvement of the garnet peridotite thermobarometry. An internally consistent set of thermodynamic parameters was derived, which allows calculation of the temperature‐pressure phase diagram for the enstatite‐pyrope join at 20–260 kbar.

Pyrope

Enstatite

Solidus

Pyroxene

Peridotite

Diopside

Grossular

10.1029/92jb01465

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Citations (50)

Melting experiments on the enstatite-diopside join at 70-224 kbar, including the melting of diopside

Contributions to Mineralogy and Petrology (1996)

Tibor Gasparik

Diopside

Enstatite

Solidus

Wollastonite

10.1007/s004100050181

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Citations (88)

System Enstatite–Diopside–Jadeite

Springer eBooks (2013)

Tibor Gasparik

Diopside

Enstatite

10.1007/978-1-4614-5776-3_9

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Citations (1)

A unique enstatite megacryst with coexisting CR-poor and CR-rich garnet, Weltevreden Floors, South Africa

American Geophysical Union eBooks (1979)

Henry O. A. Meyer Hsiao-ming Tsai John Gurney

A large (17 cm) single crystal of enstatite (En88) contains Mg-ilmenite (MgO ∼ 12 wt%) and inclusions of polyphase garnets. The major garnet is orange in color and is predominantly pyrope-almandine (Py71Al21Gr8) whereas inside this garnet is a second one that is pink in color, and Cr-rich (Cr-Py33Py28Al19Gr20). This Cr-rich garnet itself contians inclusions of Cr-diopside, chromite and ilmenite. The enclosing orange almandine garnet at the boundary with the pink Cr-rich garnet contain rounded Mg-ilmenites together with a string of elongated olivines (Fo86) that are in optical continuity. Also present in the same zone is diopside. Within the enstatite host and in close association with the polyphase garnet assemblage are calcite, Ti-phlogopite and serpentine. Although it is conceivable the Cr-rich garnet and related phases represent the remnant of an earlier pre-existing rock that underwent considerable partial melting it must also be considered that the second garnet may be metamorphic in origin. However, irrespective of the origin, based on orthopyroxene geothermometry and A12O3 content possible P and T of equilibration are in the region of 60kb and 1200°C.

Enstatite

Diopside

Almandine

Pyrope

Ilmenite

Phlogopite

Chromite

10.1029/sp016p0279

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Citations (12)

The system enstatite-wollastonite at high pressures and temperatures, with emphasis on diopside

Physics of The Earth and Planetary Interiors (1979)