Abstract
Chemical and structural zoning in plagioclase can develop in response to a number of different magmatic processes. We examine plagioclase zonation formed during the transfer of plagioclase from a granodioritic host to a monzodioritic enclave to understand the development of different zonation patterns caused by this relatively simple magma mixing process. The transferred plagioclase records two stages of evolution: crystallization of oscillatory plagioclase in the host granodioritic magma and crystallization of high An zones and low An rims in the hybrid enclave magma. High An zones (up to An72) are formed only in the hybrid enclaves after plagioclase transfer. Plagioclase from a primitive enclave, showing no or only minimal interaction with the host, is An30–43. The implication is that high An zones crystallize only from the hybrid magma and not from the primitive one, probably because of an increase in water content in the hybrid magma. Complex interactions between the two magmas are also recorded in Sr content in plagioclase, which indicates an initial increase in Sr concentration in the melt upon transfer. This is contrary to what is expected from the mixing of low Sr enclave magma with a high Sr granodiorite one. Such Sr distribution in the plagioclase implies that the transfer of the plagioclase took place before the onset of plagioclase crystallization in the enclave magma. Therefore, the mixing between high Sr granodiorite magma and low Sr enclave magma was recorded only in plagioclase rims and not in the high An zones.
Highlights
Resorption surfaces in plagioclase are common in both volcanic and plutonic rocks and resorption is commonly followed by crystallization of plagioclase with higher anorthite content
Two types of mafic microgranular enclaves occur in the granodioritic host in the Kośmin Intrusion: primitive enclaves that were not affected by magma mixing and porphyritic enclaves that were hybridized with granodioritic magma
The plagioclase from the porphyritic enclaves analyzed in this study records magma mixing processes between granodioritic host and monzodioritic magmas
Summary
Resorption surfaces in plagioclase are common in both volcanic and plutonic rocks and resorption is commonly followed by crystallization of plagioclase with higher anorthite content. Major resorption surfaces and the following increase in An content are attributed to changes in conditions of crystallization such as increase in temperature, increase of water concentration in the melt, decrease in pressure, or changes in magma composition. Such changes are commonly induced by injection of more mafic magma into the magma chamber in which plagioclase crystallizes (Ginibre et al 2002; Ginibre and Wörner 2007; Kocak et al 2011; Shcherbakov et al 2011; Viccaro et al 2010).
Sign-in/Register to view highlights & summary 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.
