The igneous rocks of the Boganclogh area, N.E. Scotland

Busrewil, M. T.; Pankhurst, R. J.; Wadsworth, W. J.

doi:10.1144/sjg09030165

Cited by 9 publications

(6 citation statements)

References 17 publications

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“…However, the QBN rocks define a reasonably coherent, if limited, fractionation trend, so that some degree of differentiation was achieved. They are similar in many respects to norites from both the Haddo Arnage, and Morven-Cabrach intrusions, and the group as a whole is believed to represent a sample of the regional basic magma which crystallized under relatively hydrous conditions (Gribble, 1967;Busrewil et al, 1973). This could account for the slight but significant differences in mineralogical signature between the QBN rocks of the Boganclogh area and the other Insch units, as shown by Figs.…”

Section: Discussionmentioning

confidence: 76%

“…The quartz-biotite norites, which form most of (Busrewil et al, 1973) are broadly similar in grain size to the MZ cumulates, but are characterized mineralogically by the relative abundance of biotite and the occurrence of interstitial quartz (associated with minor apatite and zircon). Texturally they do not appear to be cumulates, being dominated by randomly orientated and strongly zoned plagioclase crystals, interlocked with subhedral pyroxenes and poikilitic biotite, amphibole, and Fe-Ti oxides.…”

Section: Petrologymentioning

confidence: 99%

“…In addition, the MZ rocks are compared with another group of broadly similar olivine-free gabbroic rocks from the Boganclogh intrusion (believed to be a westward extension of the Main Insch mass), where they occupy a geographically intermediate position between possible equivalents of the Insch LZ and UZ. These are generally referred to as quartzbiotite norites (Busrewil et al, 1973), and similar rocks also occur in the Morven-Cabrach and Haddo House/Arnage intrusions (Wadsworth, 1982). In the interests of brevity the following abbrevia-tions are used.…”

Section: Introductionmentioning

confidence: 99%

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Silicate Mineralogy of the Middle Zone Cumulates and Associated Gabbroic Rocks from the Insch Intrusion, NE Scotland

Wadsworth

1988

Mineral. mag.

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The Middle Zone (MZ) of the Insch intrusion lies in a geographically intermediate position between the Lower Zone (LZ) and Upper Zone (UZ) cumulate sequences, but is more complicated than either in comprising two intricately associated, but texturally distinct, components, the MZ cumulates and the fine-grained granular gabbros (FGG). In addition, there is a minor group of porphyritic granular gabbros (PGG), containing abundant plagioclase phenocrysts. A further variety of gabbroic rock, namely quartz-biotite norite (QBN) occupies a similarly intermediate position in the Boganclogh extension of the main Insch mass. These principal components (MZ cumulates, FGG, and QBN) show considerable mineralogical overlap with each other and with the lower part of the UZ succession (UZa). Unlike the UZ rocks, they are essentially olivine-free (apart from the most basic granular gabbros) and consist mainly of plagioclase, orthopyroxene, and Ca-rich clinopyroxene, with accessory Fe-Ti oxides and minor interstitial biotite and/or hornblende. Mineral compositions are in the range Anv0_ss (plagioclase), Enva_44 (opx), and Caa6Mg42Fe12 to CagsMgaoF%5 (cpx), but in detail each rock group can be characterized mineralogically as well as texturally. It is concluded that the MZ cumulates and FGG (including PGG) are essentially complementary, formed in different locations, and under slightly different conditions, but in the same magma chamber. The complex relationships between them, and the apparently haphazard geographical variations in mineral compositions, may be the combined results of the magmatic events, possibly including the movement of large xenolithic fragments, and later block faulting. The substantial compositional overlap of the more evolved MZ cumulates by UZa is explained in terms of replenishment by magma of slightly more primitive (and potentially olivine-bearing) composition after the deposition of the MZ. The Boganclogh QBN is believed to represent a more hydrous fraction of the Insch MZ magma.

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Section: Discussionmentioning

confidence: 76%

Section: Petrologymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Silicate Mineralogy of the Middle Zone Cumulates and Associated Gabbroic Rocks from the Insch Intrusion, NE Scotland

Wadsworth

1988

Mineral. mag.

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“…As such, the basin is a half-graben. The basement lithology is the Ordovician Boganclogh intrusion (Busrewil et al 1973), which primarily comprises quartz-biotite-norite (an orthopyroxene-dominated gabbro) with minor serpentinite. This is intruded into the upper Proterozoic Dalradian metaturbidites of the Southern Highland Group.…”

Section: Geological Settingmentioning

confidence: 99%

An introduction to the Rhynie chert

Garwood

Oliver²,

Spencer

2019

Geol. Mag.

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The terrestrialization of life has profoundly affected the biosphere, geosphere and atmosphere, and the Geological Magazine has published key works charting the development of our understanding of this process. Integral to this understanding – and featuring in one of the Geological Magazine publications – is the Devonian Rhynie chert Konservat-Lagerstätte located in Aberdeenshire, Scotland. Here we provide a review of the work on this important early terrestrial deposit to date. We begin by highlighting contributions of note in the Geological Magazine improving understanding of terrestrialization and Palaeozoic terrestrial ecosystems. We then introduce the Rhynie chert. The review highlights its geological setting: the Caledonian context of the Rhynie Basin and its nature at the time of deposition of the cherts which host its famous fossils. There follows an introduction to the development of the half-graben in which the cherts and host sediments were deposited, the palaeoenvironment this represented and the taphonomy of the fossils themselves. We subsequently provide an overview of the mineralization and geochemistry of the deposit, and then the fossils found within the Rhynie chert. These include: six plant genera, which continue to provide significant insights into the evolution of life on land; a range of different fungi, with recent work starting to probe plant–fungus interactions; lichens, amoebae and a range of unicellular eukaryotes and prokaryotes (algae and cyanobacteria); and finally a range of both aquatic and terrestrial arthropods. Through continued study coupled with methodological advances, Rhynie fossils will continue to provide unique insights into early life on land.

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“…The Rhynie basin overlies basement rocks consisting of the Boganclough and Insch intrusions, which are comprised mainly of Ordovician quartz-biotite norites and minor serpentinites (Busrewil et al 1973), emplaced in Dalradian metamorphic rocks. The Boganclough intrusion is cut by a number of basic dykes, granites and syenites of uncertain age (Rice et al 1995).…”

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Fluids and hydrothermal alteration assemblages in a Devonian gold-bearing hot-spring system, Rhynie, Scotland

Baron

Hillier²,

Rice

et al. 2003

Transactions of the Royal Society of Edinburgh: Earth Sciences

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Hydrothermal alteration at Rhynie, Aberdeenshire, Scotland, is concentrated along a fault zone, which juxtaposes surface deposits and the mineralised feeder zone to the Rhynie hotspring system. Mineralisation consists of breccias and veins filled with quartz, chert, calcite, K-feldspar and pyrite. Associated pervasive alteration comprises a high-temperature K-feldsparquartz-illite facies (formed at 250–350°C), a medium-temperature mixed layered illite/smectitequartz-K-feldspar-chlorite-calcite facies (formed at 150–200°C) and a low-temperature mixed layered illite/smectite-chlorite-calcite facies (formed at 100 to +150°C). The fluids responsible for mineralisation were mainly moderate- to high-temperature (Th =91–360°C), low-salinity (<0·2 to 2·9 wt.% NaCl eq.) H2O-NaCl-heated meteoric fluids comparable to modern and ancient hot-spring systems. The migration of these fluids was mainly restricted to a major fault zone bounding the Devonian basin. Fluids responsible for mineralisation, alteration and cementation elsewhere in the basin were low-temperature (Th 57 to 161°C), low- to high-salinity (<0·2 to 18 wt.% NaCl eq.) H2O-NaCl fluids, which resemble basinal brines.

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The igneous rocks of the Boganclogh area, N.E. Scotland

Abstract: SYNOPSISThe Boganclogh intrusion, which appears to be a westerly extension of the Insch mass, is chemically and petrologically subdivided into three principal units which occupy roughly east-west belts.

Cited by 9 publications

References 17 publications

Silicate Mineralogy of the Middle Zone Cumulates and Associated Gabbroic Rocks from the Insch Intrusion, NE Scotland

Silicate Mineralogy of the Middle Zone Cumulates and Associated Gabbroic Rocks from the Insch Intrusion, NE Scotland

An introduction to the Rhynie chert

Fluids and hydrothermal alteration assemblages in a Devonian gold-bearing hot-spring system, Rhynie, Scotland

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