• Ntaflos, Theodoros
• Lee, Eun Young
• Kiraly, Franz
• Knierzinger, Wolfgang
• Wagreich, Michael

Abstract

This paper presents a new interactive MATLAB-based visualization and calculation tool (TETGAR_C) for assessing the<br/>provenance of detrital garnets in a four-component (tetrahedral) plot system (almandine–pyrope–grossular–spessartine).<br/>Based on a freely-accessible database and additional electron-microprobe data, the chemistry of more than 2,600 garnet<br/>samples was evaluated and used to create various subfields in the tetrahedron that correspond to calc-silicate rocks, felsic<br/>igneous rocks (granites and pegmatites) as well as metasedimentary and metaigneous rocks of various metamorphic<br/>grades. These subfields act as reference structures facilitating assignments of garnet chemistries to source lithologies.<br/>An integrated function calculates whether a point is located in a subfield or not. Moreover, TETGAR_C determines<br/>the distance to the closest subfield’s mean value. Compared with conventional ternary garnet discrimination diagrams,<br/>this provenance tool enables a more accurate assessment of potential source rocks by reducing the overlap of specific<br/>subfields and offering quantitative testing of garnet compositions. In particular, a much clearer distinction between<br/>garnets from greenschist-facies rocks, amphibolite-facies rocks, blueschist-facies rocks and felsic igneous rocks is<br/>achieved. Moreover, TETGAR_C enables a distinction between garnet grains with metaigneous and metasedimentary<br/>provenance. In general, metaigneous garnet tends to have higher grossular content than metasedimentary garnet formed<br/>under similar P–T conditions.

Topics

• impedance spectroscopy
• grain