The causes and petrological significance of cathodoluminescence emissions from alkali feldspars

Article Abstract:

The causes and petrological significance of cathodoluminescence (CL) in a variety of alkali feldspars from South Greenland were examined using CL spectroscopy, secondary ion mass spectrometry and electron paramagnetic resonance. Results showed that blue CL relates to the presence of electron holes on bridging oxygens and that some blue luminescent feldspars have an emission in the infra-red. Moreover, the difference between the red and infra-red CL emissions were observed to relate to the state of Fe3+ order across the tetrahedral sits.

Petrology, Alkalic igneous rocks, Cathodoluminescence

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Fractional crystallization and zoning in igneous feldspars: ideal water-buffered liquid fractionation lines and feldspar zoning paths

Article Abstract:

An analysis of fractionation paths and liquid fractionation lines is presented. The analysis tests these variables by setting diagrams which are based on ideal water-buffered fractional crystallization in the ternary feldspar system. It is shown that solidus or solvus paths exhibit preservation qualities either as overgrowth zones or as a crystal fraction series. In addition, the two-feldspar boundary line conditions line and path topology.

Crystallization, Fractionation, Fractional distillation

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Origin of mantled (rapakivi) feldspars: experimental evidence of a dissolution- and diffusion-controlled mechanism

Article Abstract:

An analysis describing the origin of rapakivi feldspars is presented. The analysis was based on experiments which simulated alkali feldspar dissolution in the process of magma mixing. It is shown that such a process generates plagioclase mantles with similar texture and composition as hybrid volcanic rocks. Diffusional control was exhibited by orthoclase dissolution with a rate proportional to run duration's square root.

Rapakivi

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