Abstract
It is generally accepted that pegmatites are derived from large masses of granite but, even in areas where complete mineralogical, chemical and isotopic datasets are available, the relation between pegmatites and host granitic rocks or nearby plutons is usually not simple to address. The Pavia pluton, located in the Ossa-Morena Zone (Iberian Massif), is a multiphase intrusive body constructed over ∼11m.y. by the amalgamation of several batches of magma. At the first glance, pegmatites seem to constitute a very homogeneous pegmatite field. They are mainly “intragranitic” thin tabular dikes, unzoned, layered, or with simple internal structure and are composed by the ordinary minerals that constitute the different classes of igneous rocks. They also present identical whole rock major and trace elements geochemistry and isotopic signature [(87Sr/86Sr)i=0.70434–0.70581, ɛNdt=−1.3 to −3.7 and δ18O=8.2–9.6‰] but, based on previously published geochronological data, three generations of pegmatites were identified. Two of these are coeval with the emplacement of the host granites (s.l.) at 328Ma and ca. 324Ma. The other is related to a later magmatic event at 319–317Ma. A similar and rather juvenile source is suggested for host granites (s.l.) and pegmatites but a simple and continuous process of intra-chamber magmatic differentiation is not supported by our data. It is suggested that pegmatites derived from slightly evolved batches of magma that interacted with fresh, newly emplaced, batches (from the same or from a similar source) with limited interaction with the crust. Therefore, the Pavia pegmatites do not represent the final products of magmatism at this level of the crust but slightly differentiated products of different batches of magma. This study demonstrates how long-lived magmatic systems can potentially affect the recognition of granite–pegmatite genetic relationships.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
More From: Chemie der Erde - Geochemistry - Interdisciplinary Journal for Chemical Problems of the Geosciences and Geoecology
Disclaimer: 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.