Loss of isotopic (Nd,O) and chemical (REE) memory during metamorphism of komatiites: new evidence from eastern Finland

Article Abstract:

An analysis of isotopic and chemical memory in the process of komatiite metamorphism is presented. Although komatiites are traditionally considered forisotopic and chemical composition as source rocks, they exhibit a weakness in tracing original compositional heterogeneity of the mantle. This weakness is attributed to the presence of metamorphic recrystallization. REE evaluation shows the inability of major or trace elements from being identified with olivinee and pyroxene fractionation.

Finland, Composition, Komatiite

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"Pseudosinhalite," a new hydrous MgAl-borate: synthesis, phase characterization, crystal structure, and PT-stability

Article Abstract:

The new synthetic phase Mg(sub2)Al(sub3)O[BO(sub4)](sub2)(OH) called pseudosinhalite is analyzed. It is argued that the structure and chemical composition of pseudosinhalite is similar to the mineral sinhalite MgAl[BO(sub4)]. It also grows hydrothermally from appropriate bulk compositions ranging from 4-40 kbar and temperatures that increase with pressure and breaks down to sinhalite + corundum + water at high temperatures.

Rocks, Metamorphic, Metamorphic rocks

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The stability of merwinite in the system CaO-MgO-SiO(2)-H(2)O-CO(2) with CO(2)-poor fluids

Article Abstract:

The stability of merwinite in the binary H(2)O-CO(2) fluids is analyzed. Results show that in a H(2)o-CO(2) fluid mixture, merwinite is stable at low pressure (0.5-1.0 kbar), low carbon dioxide content (0.02-0.1) and high temperature (greater than 700 degrees Celsius). Moreover, the metasomatic fluid involved in the formation of the contact aureole at Crestmore, CA appears to have had a carbon dioxide content of 0.1.

California

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