Using a titanium-in-quartz geothermometer for crystallization temperature estimation of the Palaeoproterozoic Suursaari quartz porphyry

• Published in: Estonian Journal of Earth Sciences
• Main Authors: Kairi Ehrlich, Evelin Verš, Juho Kirs, Alvar Soesoo
• Format: Article in Journal/Newspaper
• Language: English
• Published: Estonian Academy Publishers 2012
• Subjects: volcanics; quartz porphyry; crystallization temperature; Ti-in-quartz geothermometer; laser ablation inductively coupled plasma mass spectrometry; Suursaari; Geology; QE1-996.5; Fennoscandian
• Online Access: https://doi.org/10.3176/earth.2012.4.01; https://doaj.org/article/212a23e745d9412bb0683ab9cbe5d044

The Suursaari volcanic sequence represents volcanic activity related to Wiborg Batholith rapakivi intrusions in the southern part of the Fennoscandian Shield. The estimated pressure conditions for batholith granitic rocks are 1–5 kbar and crystallization temperatures range from 670 to 890 °C. To describe the temperature regime of the Suursaari volcanic system, a rock sample was taken from the Mäkiinpäällys Mountain outcrop and analysed with laser ablation inductively coupled plasma mass spectrometry. Sample spots were selected from quartz phenocrysts and groundmass. Quartz crystallization temperatures were calculated by the Ti-in-quartz method that takes into account rutile equilibrium and Ti activity in each phase. The calculated crystallization temperatures of the Suursaari quartz porphyry are in the range of 647–738 °C. The results show that the Suursaari quartz porphyry contains two generations of quartz which can be distinguished on the basis of crystallization temperatures: phenocrysts crystallized at higher and groundmass quartz at lower temperature.