A preliminary study of the structure, stratigraphy and metamorphism of some contact rocks of the western Andes, near the Quebrada Venado Muerto, Peru

Abstract

The sequence and structure of the volcanic rocks of a small area lying within the main belt of plutons of the Peruvian Andes were mapped and are here described. Metamorphic zoning of the calcareous aureole minerals was shown to be similar to that described elsewhere, e.g. wollastonite. diopside, hornblende with increasing distance from the contact. The mineral assemblages and their spatial and textural character indicate rapid heating of the aureole, with only a short time at maximum temperatures. The complex mineralogy in individual rocks is interpreted in terms of changing physical conditions during the thermal event. The sequential assemblages are the result of changes in activity of CO,, H,O and Fea+ in particular.

The origin of trapiche-like inclusion patterns in quartz from Inner Mongolia, China

“…A comprehensive review of trapiche emeralds and a detailed formational model is given by Pignatelli et al (2015). The trapiche morphology and specific internal textural characteristics, including distinct sector boundaries within coherent single crystals resulting from a high density of inclusions along those boundaries, has been observed in other minerals including andalusite (chiastolite variety; Rice and Mitchell, 1991;Rice, 1993), garnets (Harker, 1950;Atherton and Brenchley, 1972;Wilbur and Ague, 2006), corundum (Müllenmeister and Zang, 1995;Schmetzer et al, 1996Schmetzer et al, , 1998Sunagawa, 1999;Garnier et al, 2002aGarnier et al, , 2002b, and tourmaline (Hainschwang et al, 2007;Schmetzer et al, 2011).…”