The Igneous Rocks of the Stanner-Hanter District, Radnorshire

Holgate, Norman; Hallowes, K. A. Knight

doi:10.1017/s0016756800071971

Cited by 17 publications

(7 citation statements)

References 9 publications

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“…It is contained within splays of the Church Stretton Fault, part of the Welsh Borderland Fault System (WBFS), and was considered an exposure of the basement to the Wrekin Terrane by Pharaoh et al (1987). Although contacts are poorly exposed, the inlier is interpreted to be overstepped by strata of Silurian age on its southern Holgate & Hallowes, 1941;Woodcock, 1988). Filled triangles indicate the summits of Hanter Hill (HH) and Stanner Hill (SH).…”

Section: Geology Of the Stanner Hanter Complexmentioning

confidence: 99%

“…Co-ordinates are British National Grid. and eastern margin, but faulted along its northern contact (Holgate & Hallowes, 1941;Fig. 2).…”

Section: Geology Of the Stanner Hanter Complexmentioning

confidence: 99%

“…(1987). Although contacts are poorly exposed, the inlier is interpreted to be overstepped by strata of Silurian age on its southern and eastern margin, but faulted along its northern contact (Holgate & Hallowes, 1941; Fig. 2).…”

Section: Geology Of the Stanner Hanter Complexmentioning

confidence: 99%

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A new, high precision U–Pb date from the oldest known rocks in southern Britain

Schofield

Millar²,

Wilby

et al. 2009

Geol. Mag.

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A new high precision U-Pb zircon age of 710.8 ± 1.5 Ma for granophyric granitic rock from the Stanner Hanter Complex of the Welsh Borderland lies just within error of an older Rb-Sr isochron age. εNd values of −0.3 and −1.2 combined with T DM of 1394 Ma and 1468 Ma indicate that the magma incorporated an older crustal source component. The Nd data highlight differences with western Avalonia, the widely considered Late Neoproterozoic north American counterpart to southern Britain, and point toward a closer similarity with other Peri-Gondwanan terranes that incorporate older, cratonic source material.

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Section: Geology Of the Stanner Hanter Complexmentioning

confidence: 99%

“…Co-ordinates are British National Grid. and eastern margin, but faulted along its northern contact (Holgate & Hallowes, 1941;Fig. 2).…”

Section: Geology Of the Stanner Hanter Complexmentioning

confidence: 99%

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A new, high precision U–Pb date from the oldest known rocks in southern Britain

Schofield

Millar²,

Wilby

et al. 2009

Geol. Mag.

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“…Accordingly, we are reluctant to make any correlations with such other Precambrian successions solely on the basis of lithological resemblance. In addition, the igneous rocks of Old Radnor represent an intrusive complex, principally of gabbros and dolerites, but also with granites and granophyres (Holgate & Hallowes, 1941). There appears little ground for correlation, therefore, with rocks of the Llangynog area.…”

Section: Comparison With Other Southern British Precambrian Rocksmentioning

confidence: 99%

The stratigraphy and setting of the Precambrian rocks of the Llangynog Inlier, Dyfed, South Wales

Cope

Bevins

1993

Geol. Mag.

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Detailed mapping of the Precambrian rocks of the Llangynog Inlier, made possible by a series of new exposures, has allowed the establishment for the first time of the 1100 m thick succession within the Precambrian rocks of the area. All boundaries of the Precambrian rocks with younger strata in the area are either faults or unconformities. Some 350–400 m of rhyolitic lavas form the oldest rocks seen in the area; they are extensively silicified and devitrified and show little of their original texture, although flow-banding is visible in some outcrops and the presence of perlitic and snowflake textures imply that originally they were glassy in part. These lavas are succeeded by a varied succession dominated by volcaniclastic siltstones showing evidence of shallow water deposition and containing medusoids and trace fossils of Ediacaran age. Interbedded in the sediments are basaltic lavas, autobreccias and rare hyaloclastites displaying textural features characteristic of submarine eruption, and rhyolitic pumiceous and shardic ash-flow tuffs. The name Coomb Volcanic Formation is proposed for this succession, within which are recognized two members, a lower Castell Cogan Rhyolite Member succeeded by the Coed Cochion Volcaniclastic Member. In association are varied intrusions, comprising both dolerites and dacites. A palaeoenvironmental model, built on evidence of petrography, palaeontology and sedimentology is that of shallow water to emergent volcanic islands.

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“…Pharaoh et al (1987) described the geochemistry of Uriconian volcanic rocks as bimodal, identifying a within-plate character and a minor subduction component and concluding that they were erupted in an ensialic basin at the margin of Gondwana. These comprise chiefly dolerites and gabbros, but have been little studied since their description by Holgate & Hallowes (1941). Further to the southwest along the Welsh Borderland Fault System, two small outcrops of Neoproterozoic rocks make up the Stanner-Hanter Complex in the vicinity of Stanner Rocks.…”

Section: Introductionmentioning

confidence: 98%

Geochemical character of Neoproterozoic volcanic rocks in southwest Wales

et al. 1995

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Volcanic rocks of Neoproterozoic age form several fault-related inliers in Wales and the Welsh Borderland. Those in North Wales and the Borderland have been investigated recently, while those in southwest Wales remain little studied. In southwest Wales, basic to intermediate lavas and related volcaniclastic rocks and silicic tuffs in the St David's area comprise the Pebidian Supergroup, which is intruded by minor basic intrusions, while the Coomb Volcanic Formation, exposed farther east around Llangynog, is composed of basic and silicic lavas and silicic tuffs, intruded by a single dacite sill and numerous dolerite sills. New geochemical data show that both the Pebidian and Coomb basalts have subduction-related characteristics. The Coomb basalts are geochemically similar to those of the Uriconian Group of the Welsh Borderland, while the Pebidian basalts bear a similarity to volcanic rocks recovered from the Bryn-teg Borehole, in the Harlech Dome. Uriconian-type volcanic rocks may underlie much of the Midlands Microcraton, with the Welsh area underlain by volcanic rocks of Pebidian type.

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The Igneous Rocks of the Stanner-Hanter District, Radnorshire

Cited by 17 publications

References 9 publications

A new, high precision U–Pb date from the oldest known rocks in southern Britain

A new, high precision U–Pb date from the oldest known rocks in southern Britain

The stratigraphy and setting of the Precambrian rocks of the Llangynog Inlier, Dyfed, South Wales

Geochemical character of Neoproterozoic volcanic rocks in southwest Wales

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