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The geology and geochemistry of the area west of Loch Killin, Inverness-shire

The geology and geochemistry of the area west of Loch Killin, Inverness-shire Thumbnail


Abstract

The area under study, which lies west of Loch Killin, Inverness-shire, was mapped during the years 1975-1978.
The continuous sequence of pelitic and psammitic metasediments comprises four formations and each is characterised by dominant lithotypes and distinctive minor metased- imentary facies. Lithotypes are described for each formation. Sedimentary structures are described in some detail, allowing an insight into the depositional environment.
The area has been subjected to polyphase folding and four phases (F1-F4) are determinable. Morphology and distribution are considered for each fold phase. Geometrical analysis is applied to selected folds. Production of the regional foliation (S1) accompanied F1 with later fabrics forming with subsequent deformational episodes. The S1 fabric is analysed graphically (using selected smaller areas)thus elucidating trends and the influence of later phases of folding.
All lithotypes are described petrographically and the petrology of both white and green calc-silicates is discussed in some detail, with reactions postulated to account for mineral assemblages. The white calc-silicates are further used to establish metamorphic zones which aid in assessing the metamorphic grade in the absence of a full sequence of Barrovian zonal index minerals. Timing of metamorphism is related to deformational episodes using textural information and two major metamorphic peaks (M1 and M2) are isolated.
Minor intrusive bodies of the Newer Granites and two ' petrographically distinct suites of granophyres occur in the area. Selected samples are described and compared. Small suites of amphibolites and meta-appinites are also studied.
Chemical analyses of 115 samples are presented and the geochemical study appraises the results from various suites in order to link chemical and mineralogical variations, to discover the chemical bases for differences between groups and to compare Killin rock types with similar lithologies from other regions.

Publicly Available Date Mar 28, 2024

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