Abstract
In order to improve understanding of how accessory garnet crystallizes in igneous rocks, and evaluate it as a mineral recorder of magma history, we analyzed δ 18 O of garnets from the Hallowell and Togus plutons in south-central Maine (United States) by laser fluorination, and in situ by ion microprobe. Two types of garnet are recognized, magmatic and locally derived peritectic. Traverses of some single crystals show both gradual and abrupt changes of δ 18 O(garnet), commonly >1‰, while other garnet grains are isotopically homogeneous. Rimward increase of δ 18 O in many crystals indicates that garnet grew while high δ 18 O metamorphic wall rocks were assimilated. Peritectic grains have a complementary record of the transfer of high δ 18 O melts to the plutons. In some rocks, δ 18 O varies among neighboring grains, evidence that crystals grew episodically or were juxtaposed from different sources during magma mixing. Garnet faithfully records changing magmatic δ 18 O, and is a valuable tool to decipher magma petrogenesis.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
