May 9, 2023 · Propylitic alteration is a type of hydrothermal alteration that occurs in volcanic and plutonic rocks. It is characterized by the alteration of primary minerals, such as feldspar and quartz, to secondary minerals, such as chlorite, epidote, and sericite. Propylitic alteration typically occurs at lower temperatures (less than 200°C) and ...

sericite-chlorite, quartz-chlorite, and finally quartz-sulfide (Zierenberg and others, 1988). The completely silicified rocks were originally mapped as “chert exhalite,” but careful mineralogical, geochemical, and isotopic studies showed the presence of relict igneous chromium spinel, proving massive hydrothermal replacement.

Microprobe analyses for sericite, chlorite, and epidote are recalculated to structural formulas by the method employing oxygen anion equivalents. The sericite has the general composition of muscovite, but is moderately phengitic, and two samples have …

The early stage of the hydrothermal activity has produced extensive propylitisation and potassic alteration (orthoclase, biotite, sericite) associated with the central part of the quartz-micromonzodioritic porphyry stock.

Sericite is grungy-looking fine-grained stuff that commonly replaces feldspars. Close examination of sericite reveals that at least some of it is fine-grained white mica. Because it is generally made up of very small crystals, its birefringence is irregular and generally low.

section. The replacement of plagioclase by sericite is associated with alteration of biotite to chlorite, and both alterations are associated with development of epidote. In the plagioclase, the sericitization is generally unevenly developed within individual crystals, and is

Jan 8, 2018 · The sericite phyllic alteration zone has extended in the porphyry quartz–monzonite and granodiorite intrusive bodies of the Kerver and Bagh-e-Golan deposits. In this alteration, K-feldspar and plagioclase minerals were replaced by sericite. Sericite, hydrothermal quartz, and pyrite are the major products of this alteration.

Alteration zones in Onzon-Kanbani area can be generally described as three types of alterations: silicic (banded and crustiform banding), sericite-illite and porpylitic alteration (Fig.6) on the...

Clinozoisite and epidote form a solid solution series related by substitution of Fe 3+ for Al. Clinozoisite has composition close to Ca 2 Al 3 Si 3 O 12 (OH). Epidote has general formula Ca 2 (Al,Fe 3+) 3 Si 3 O 12 (OH). The most Fe-rich epidotes have about 35% of …

Dec 1, 2023 · In this study, comprehensive petrographic analysis reveals that in the propylitic zone, epidote mainly replaced hornblende (Ep1a) and plagioclase phenocrysts (Ep1b), coexisting with chlorite, apatite and titanite.