Date of Award
5-12-2024
Degree Type
Thesis
Degree Name
Master of Science (MS)
Department
Earth & Environmental Sciences
Advisor(s)
Scott Samson
Keywords
Adirondack Mountains;Geochemistry;Grenville Province;Mesoproterozoic;Temperature;Zircon
Subject Categories
Earth Sciences | Geochemistry | Physical Sciences and Mathematics
Abstract
The Grenville Province (1200-980 Ma) is known to consist of many rocks which are abundant in zircon. This is seen by the large size of Grenville-age zircons and their abundance in the detrital record. A possible explanation for this is the temperature at which these rocks formed. This hypothesis states that the melts which formed the zircon-rich Grenville lithologies were exceptionally high temperature, enabling them to incorporate a significant amount of zirconium. As it is believed that most zirconium in a melt is incorporated into zircon, a high concentration of zirconium in a magma would crystallize an abundance of zircon. To test this hypothesis, we performed four types of thermometry (calculation of liquidus temperatures, thermodynamic calculation of zircon onset temperatures, zircon saturation temperatures, and Ti-in-zircon temperatures) on nine samples from the Adirondack Mountains, NY. Trace element analyses of zircon crystals were performed with both SHRIMP and LA-SF-ICPMS methods, while whole-rock geochemistry was obtained through XRF. Calculated liquidus temperatures ranged from 1050-1300°C, while temperatures from zircon onset and zircon saturation thermometry ranged from 973-1024°C and 822-964°C respectively. The highest calculated temperatures for each sample using Ti-in-zircon thermometry ranged from 803-921°C. Comparing these Grenville temperatures with published thermometry results, these temperatures are among the highest for granitic bodies. This suggests that the zircon-rich rocks of the Grenville Province formed from high temperature magmas, supporting our hypothesis that the abundance of Grenville-age zircons is a result of the temperature of the melts these rocks formed from. The reason these magmas were high temperature may be related to basaltic magmas which pooled beneath the crust, causing partial melting during Grenville orogenesis. Further research will be required to determine the validity of this possibility.
Access
Open Access
Recommended Citation
St. Denny, John, "Investigating the Formation of the Zirconium-Rich Lithologies of the Grenville Province Using Zircon Thermometry of Granitoids from the Adirondack Mountains" (2024). Theses - ALL. 889.
https://surface.syr.edu/thesis/889
