Ferropericlase, (Mg,Fe)O, is the second-most abundant mineral of Earth's lower mantle. With increasing pressure, the Fe ions in the material begin to collapse from a magnetic to nonmagnetic spin state. We present a finite-temperature first-principles phase diagram of this spin crossover, finding a broad pressure range with coexisting magnetic and nonmagnetic ions due to favorable enthalpy of mi...

Paragonite has been found in two chloritoid-chlorite-mica schists from the Dalradian, north of Stonehaven. The principal bulk-chemical constraints on the occurrence of this mineral within the chloritoid zone appear to be the ratios of soda to potash and the A1203 contents of the rock. The composition of paragonite coexisting with muscovite indicates a crystallization temperature of 550 ~ for ro...

Multigrain X-ray diffraction (XRD) can be used to accurately calculate the unit cell parameters of individual mineral phases in a mineral assemblage contained in a diamond anvil cell (DAC). Coexisting post-perovskite (ppv) and H-phase were synthesized at 119 GPa and 2500 K from (Mg0.85Fe0.15)SiO3 in a laser-heated DAC. The unit cell parameters of the ppv and coexisting H-phase were determined u...

This experimental study examines the mineral/ melt partitioning of incompatible trace elements among high-Ca clinopyroxene, garnet, and hydrous silicate melt at upper mantle pressure and temperature conditions. Experiments were performed at pressures of 1.2 and 1.6 GPa and temperatures of 1,185 to 1,370 C. Experimentally produced silicate melts contain up to 6.3 wt% dissolved H2O, and are satur...

Oxygen isotopic compositions of silicate inclusions in IVA iron meteorites have been measured with an in situ UV laser microprobe technique. The homogeneity of oxygen isotopic compositions within and among individual mineral grains has also been examined. Oxygen isotope fractionations between coexisting mineral pairs were utilized in oxygen isotope thermometry. Our measured O values, ranging fr...

Remote observation by the reflectance spectrometers onboard the Japanese lunar explorer Kaguya (SELENE) showed the purest anorthosite (PAN) spots (>98% plagioclase) at some large craters. Mineralogical and petrologic investigations on the feldspathic lunar meteorites, Dhofar 489 and Dhofar 911, revealed the presence of several pure anorthosite clasts. A comparison with Apollo nearside samples o...