Identifying E-type and N-type morb picrites from Paallavvik Island, Baffin Island, Canada

Mooney, Ryan (2025) Identifying E-type and N-type morb picrites from Paallavvik Island, Baffin Island, Canada. MSc(R) thesis, University of Glasgow.

Abstract

A new suite of 27 igneous rocks were collected during a 2021 expedition to Paallavvik Island, funded by Red Bull. Picrites from Baffin Island have been previously investigated due to their high MgO of up to 22 wt.%, high 3He/4He ratio of 49.5Ra and the two geochemical distinct types of N-type and E-type MORB (Francis, 1985; Robillard et al., 1992; Fitton et al.; 1997; Mahoney et al., 2002; Stuart et al., 2003; Yaxley et al., 2004; Starkey, 2009; Maisonneuve, 2012). Within this study, the geochemistry and mineralogy of the new suite of igneous rocks were investigated and compared to previously published data.

Using XRF and LA-ICP-MS, the samples were analysed and then split into the two groups, N type and E-type MORB. The conditions of separation used were K/Ti </> 0.2 and (La/Sm)N </> 0.8, where less than for both conditions meant N-type MORB and more than meant E-type MORB (Robillard et al., 1992; Mahoney et al, 2002; Stuart et al., 2003; Starkey, 2009; Starkey et al., 2009; Maisonneuve, 2012). Using SEM, EMPA and LA-ICP-MS, the mineralogy and geochemistry of the minerals were investigated.

The major and trace element relationships against MgO were found to agree with previously published results (Francis, 1985; Robillard et al., 1992; Holm et al., 1993; Larsen and Pedersen, 2000; Yaxley et al., 2004; Starkey, 2009; Starkey et al., 2009). Using the conditions of separation, samples were split into 3 categories – N-type MORB, E-type MORB and those that failed one condition but not the other. N-type MORB samples were found to be 1, 4, 6, 7, 9, 13, 15, 16, 24 and 25. E-type MORB samples were 3, 5, 10, 12, 14, 20, 21, 23 and 26.

Contamination by mantle metasomatism was investigated after it was found that the Na2O/TiO2 ratio agrees with other studies at ~1.48 (σ = 0.31) for these samples, meaning that the lavas erupted through thick lithosphere and so have the potential to be contaminated (Su, 2003; Jackson and Dasgupta, 2008; Starkey, 2009). However, the investigation was inconclusive due to poor quality of data.

The olivine minerals analysed had a forsterite range of Fo34 to Fo79. In comparison to previously published studies, this is around 10% less, which may have been down to the standards used (Francis, 1985; Larsen and Pedersen, 2000; Starkey, 2009; Maisonneuve, 2012). Continuous trends of CaO, NiO and Fo% against Cr2O3, as well as no difference in Fo% for different sizes of olivines showed that the olivines are all sampling the same source (Starkey, 2009; Starkey et al., 2012).

Further work is advised for the study of the samples. By measuring 3He/4He of the melt inclusions and comparing it with previously published studies – e.g. Stuart et. al. , 2003. This will show whether the samples have a relationship with a primitive undegassed mantle reservoir. Furthermore, SIMS should also be used to investigate hydrogen and nitrogen isotopes within the melt inclusions and surrounding minerals. Hydrogen and nitrogen isotopes can help determine how the Earth became rich in volatiles and offer more information about the geochemistry of the deep mantle.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Subjects: G Geography. Anthropology. Recreation > GB Physical geography; Q Science > QD Chemistry; Q Science > QE Geology
• Colleges/Schools: College of Science and Engineering > School of Geographical and Earth Sciences
• Supervisor's Name: Hallis, Dr. Lydia and Neill, Dr. Iain
• Date of Award: 2025
• Depositing User: Theses Team
• Unique ID: glathesis:2025-85431
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 03 Sep 2025 12:38
• Last Modified: 03 Sep 2025 12:41
• Thesis DOI: 10.5525/gla.thesis.85431
• URI: https://theses.gla.ac.uk/id/eprint/85431