The geochemistry of the Connemara gneiss complex, Co. Galway, Ireland

Keeling, Barry Edward (1981) The geochemistry of the Connemara gneiss complex, Co. Galway, Ireland. PhD thesis, University of Glasgow.

Abstract

An area of about 100 sq.km. immediately north of the Galway granite has been studied. The area encompasses the central part of the Connemara Gneiss complex, a syntectonic suite of basic, intermediate and acidic intrusives and migmatised Dalradian sediments. 50 rock samples from the complex have been analysed by X-Ray fluorescence methods for all major elements and up to 13 trace elements (Cr, Co, Ni, Rb, Sr, Y, Zr, Nb, Ba, La, Ce, Pb, Th). In addition, 41 of these rock samples have been analysed by neutron activation methods for up to 9 trace elements (La, Ce, Nd, Sm, Eu, Tb, Yb, Lu, Sc).These data together with microprobe analyses of 60 mineral grains from the samples,3re presented and used to deduce the petrogenesis of the Gneiss complex. The orthomagmatic rocks were intruded into the pelites, semipelites, and quartzites of the Dalradian Cashel Formation, during the period between the onset of the D2 deformation and the completion of the D3 deformation. The initial intrusions were basaltic in composition and they were intruded during D2 mainly as thick sheets and masses, which are conformable to the F2 foliation in the country rocks. These intrusions were then fragmented and, the rocks amphibolitised during the combined D3 deformation and M3 metamorphism. The cause of the M3 event was the intrusion of the intermediate magmas, which solidified to form the tonalitic orthogneisses. High degrees of partial melting occurred in the aureole zone of these intermediate magmas, forming the paragneiss. There is field evidence for large scale assimilation of paragneiss by the magma. The intrusion of small amounts of granitic magma, during the latter stages of D3, completed the magmatic phase.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > QE Geology
• Colleges/Schools: College of Science and Engineering
• Supervisor's Name: Leake, Professor B.E.
• Date of Award: 1981
• Depositing User: Enlighten Team
• Unique ID: glathesis:1981-84194
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 13 Mar 2024 11:40
• Last Modified: 14 Mar 2024 14:13
• Thesis DOI: 10.5525/gla.thesis.84194
• URI: https://theses.gla.ac.uk/id/eprint/84194