Porosity evolution and mineral paragenesis during low-grade metamorphism of basaltic lavas at Teigarhorn

• Main Authors: Philip S. Neuhoff, Dennis K. Bird
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1999
• Subjects: Teigarhorn; Iceland
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.530.5769; http://earth.geology.yale.edu/~ajs/1999/06.1999.02Neuhoff.pdf

ABSTRACT. Low-grade alteration of basaltic lavas at Teigarhorn, eastern Iceland, resulted in three distinct stages of mineral paragenesis that correlate to events in the burial and intrusive history of Icelandic crust. Metasomatism and brittle deformation during the paragenetic stages dramatically affected the paleo-hydrology of the lavas and formed temporally distinct mineral assemblages. The lavas initially contained up to 22 percent total porosity concentrated near the tops and bottoms of individual lava flows. Celadonite and silica (Stage I) precipi-tated along the walls of primary pores prior to deep burial of the lavas and occluded 8 percent of the initial porosity. During burial (Stage II), hydrolysis of olivine and basaltic glass led to the formation of mixed-layer chlorite/smectite clays in the matrix of the lavas and as rims filling 40 percent of the volume of primary pores. Chlorite contents in Stage II mixed-layer clay rims increased from 20 to 80 percent during the infilling of individual vesicles, reflecting increas-ing temperatures with time as the lavas were buried. The end of Stage II occurred after burial and is represented by filling of 40 percent of total primary porosity