Physico-chemical alteration of pyroxene in coastal environments: Empirical constraints from New Zealand and the Azores
- Author
- Juan J. Kasper-Zubillaga, David M. Buchs, Duncan D. Muir, Lizeth Carlos-Delgado, Elsa Arellano-Torres, León Felipe Álvarez-Sánchez
- Year
- 2024
- Journal / Source
- Sedimentary Geology
- Volume
- 465
- Number
- 106632
- Keywords
- Muriwai
- Summary
- Developing approaches to determine the modes of transport and weathering of mafic detrital minerals in natural sedimentary environments is critical to our understanding of sediment production, dispersal and provenance, as well as carbon capture under natural and enhanced weathering regimes. We integrated the characterisation of morphological and surface textures with the surface composition of recent detrital clinopyroxene grains concentrated in a sandy coastal area from the western North Island of New Zealand and a rocky shore area of Santa Maria Island in the Azores Archipelago. Using the compactness shape descriptor, 341 grains were subdivided into elongated, elongated angular, euhedral, angular and subangular groups, with each group further characterised using morphological and microtextural indicators of abrasion, breakage and dissolution/chemical weathering. In both studied environments, the clinopyroxenes are dominated by elongated to angular shapes with flat cleavage surfaces and conchoidal fractures. This is consistent with dominant subaqueous transport by rivers and longshore currents for New Zealand, and dominant wave action with limited sediment supply by rivers along the rocky shore of Santa Maria.