Palaeomagnetism of Late Precambrian or Cambrian diorites from Leicestershire, U.K.

Duff, B. A.

doi:10.1017/s0016756800028594

Cited by 6 publications

(5 citation statements)

References 7 publications

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“…cleaning, and unblock close to the Curie point of magnetite ( Figure 6). Duff (1980) recognized a somewhat steeper component with similar declination (D = 292O, I = 72') from Old Croft quarry between sites 13 and 16 of this study. A south to southwesterlydirected component is present at site 17 and appears as a higher blocking temperature component in a few other samples (site 15 in Figure 6).…”

Section: Charnwood Plutonssupporting

confidence: 70%

“…The azimuth of this characteristic remanence vanes from EN€ to N. Sometimes this distribution is observed within individual sites and cannot be solely attributed to tectonic effects. The component directions from sites 6 to 8 are similar, but have somewhat more easterly azimuths than results obtained by Duff (1980) from the same locations. (These latter results yielded a mean for three sites of D = 1 8 O , I = 48').…”

Section: A the Charnian Plutonsmentioning

confidence: 50%

“…They do not in general correlate with possible post-Silurian remagnetization events (Figure 11). Hematite is variably developed in some of the volcanic units: in some cases (site 6 in Figure 5) it is recognized by its signature as an unsaturated peak in thermomagnetic determinations (Duff 1979) and in a few sites (12 in Figure 5) it appears to be the sole carrier of the remanence. In most cases however, components carried by hematite comprise only a small fraction of the total remanence and the dominant magnetite-resident components isolated here (whether primary or secondary) must be interpreted in the context of the pre-Silurian history of the region.…”

Section: E Regional Assessment Of the Uriconian Resultsmentioning

confidence: 99%

“…Palaeomagnetic investigations of this basement have aimed to establish an apparent polar wander (APW) record which will enable the region to be related to other comparable terranes, such as the Cadomian and Avalonian, which experienced similar tectonic and magmatic histories during the same interval of Late Precambrian and early Cambrian times. Results from a range of palaeomagnetic studies published by Lomax and Briden (1977), Piper (1979), Duff (1980), Thorpe er al. (1984), andPiper (1982) have contributed towards this general objective.…”

Section: Regional Settingmentioning

confidence: 99%

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A palaeomagnetic study of the Charnian, Caldecote, and Uriconian volcanics and plutons, central England

Piper¹,

Strange²

1989

Geological Journal

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This palaeomagnetic study has investigated intrusive and extrusive calc-alkaline igneous rocks comprising the preOrdovician basement of central England and the Welsh Borderlands and dated ca. 560-530 Ma. Demagnetization studies resolve a range of magnetic components in both the older volcanic successions comprising the eastern Uriconian volcanics, and in the younger intrusive episodes comprising the Charnwood and South Leicestershire outcrops. PostOrdovician overprinting is largely absent and the remanence record dates from ca. 560-420 Ma. Within this time interval field tests are inadequate to confirm a primary origin and some components may be overprints acquired in immediate post-Uriconian (Cadomian) or during late Ordovician (early Caledonian) thermotectonic events. A first order continuity is recognized on a palaeomagnetic scale between the data from the Midlands-Welsh Borderlands and the terranes exposed in Anglesey and Southwest Wales. The British terranes moved through low latitudes during the interval represented by the Uriconian episode; they crossed the palaeoequator during the folding of these rocks and prior to emplacement of the later intrusive suite. Collectively they had rotated through cu. 170' and moved into intermediate latitudes by mid-Lower Cambrian times. Post-Lower Cambrian movements on the Malvernian lineament are a possible explanation for second order differences between the palaeomagnetic records of the English Midlands and the Welsh Borderlands; the largest possible regional rotation here is a ca. 90' movement of the Charnwood block with respect to the other outcrops. Correlation with the Gondwana APW path places the Anglo-Welsh basement in the vicinity of a comparable calc-alkaline volcanic province linked to a subducting plate margin in the Afro-Arabian area. Subsequent continental breakup led to termination of this volcanic activity and establishment of a passive marine shelf environment later in Lower Cambrian times.KEY WORDS Charnian Caldecote Uriconian Palaeomagnetism Cambrian 1. REGIONAL SETTING For the purposes of this paper the Late Precambrian-Lower Cambrian basement of England and Wales is regarded as that part of the geological column south of the Iapetus suture which predates deposition of the Lower Cambrian quartzites in a quiescent shelf environment during the latter part of Lower Cambrian times (ca. 535 Ma). This basement only appears as outcrop at a number of small and scattered locations. The exposed rock units fall into four broad divisions namely: (1) low grade metamorphic rocks, mostly of igneous derivation (the Malvernian, Stanner-Hanter Complex, Rushton schist, and Primrose Hill gneiss); (2) the Charnian sedimentary and volcanoclastic succession; (3) the Charnian, Caldecote, and Unconian volcanics and plutons; and (4) the Longmyndian sedimentary succession. Chemical and isotopic evidence imply a derivation of the igneous and metamorphic suites from crust with an antiquity no greater than ca. lo00 Ma (Thorpe et al. 1984). This terrane clearly contrasts with crust ...

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Section: Charnwood Plutonssupporting

confidence: 70%

Section: A the Charnian Plutonsmentioning

confidence: 50%

Section: E Regional Assessment Of the Uriconian Resultsmentioning

confidence: 99%

Section: Regional Settingmentioning

confidence: 99%

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A palaeomagnetic study of the Charnian, Caldecote, and Uriconian volcanics and plutons, central England

Piper¹,

Strange²

1989

Geological Journal

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“…New data from Jersey (including the results from the Jersey volcanics and dykes described in this paper), the Armorican massif (Duff 1979a), Leicestershire (Duff 1979b), and a minor study in North Wales (Duff 1978b) (1973), McElhinny & Cowley (1977), J. C .…”

Section: Introductionmentioning

confidence: 96%

The palaeomagnetism of Jersey volcanics and dykes, and the Lower Palaeozoic apparent polar wander path for Europe

Duff

1980

Geophys J Int

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Stable natural remanent magnetization (NRM) in the Jersey Volcanics and in a single rhyolite dyke was probably acquired during the Cambrian before folding of the volcanics in the Cadomian Orogeny. After dip correction, the volcanics yield a palaeomagnetic pole at 323" E, 52" N (dp = 33", dm=35"). In Jersey dolerite dykes three groups of stable NRM directions are recognized, with palaeomagnetic poles at 248' E, 26" N (dp = lo", dm = 20°), 339" E, 1" S (dp = 9", dm = 12"), and 336" E, 31" S (dp = 5", dm = 9"). Comparison with the European apparent polar wander path implies that stable NRM in these groups was acquired respectively during Late Precambrian or early Cambrian, Siluro-Devonian and middle Carboniferous time. The stable NRM of the Jersey lamprophyre dykes yields a palaeomagnetic pole at 322" E, 16" N (dp = 31°, dm = 38") and is probably of Silurian or Devonian age.These palaeomagnetic poles and other new data determined by the author for the Armorican Massif can be fitted to a common apparent polar wander path for Europe, and this implies that the basement of Lower Palaeozoic Europe extended from the Baltic Shield at least as far south as the Armorican Massif. The Hercynian Orogeny in these parts of Europe was therefore probably intracratonic. This polar wander path implies that in early Cambrian time the pole did not move significantly relative to Europe, but that this was followed by a large middle to late Cambrian polar shift which corresponded to rapid drift of Europe across the South Pole.

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Palaeomagnetism of late Precambrian-Cambrian volcanics and intrusives from the Armorican Massif, France

Mbipom

Hutton

1983

Geophys J Int

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Results are presented for a magnetotelluric and magnetovariational study in northern Scotland. For nine of the 20 sites at which observations were made the results of the analysis are presented fully together with one-dimensional (1-D) Monte-Carlo inversions for representative sites from the Lewisian Foreland, the North-west Highlands, the Great Glen region and the Grampian Highlands. For the remaining sites, the results are summarized. The 1-D models of all sites situated in a traverse extending from the Lewisian Foreland to the neighbourhood of the Highland Boundary Fault have been used as the basis for preliminary 2-D modelling. Maps of magnetic field induction vectors and transfer functions for an inducing field perpendicular to the average geological strike are presented for periods of 23-819s. The 2-D conductivity models were constrained by both the magnetotelluric and magnetovariational responses. The period range of observation in this study was too limited t o resolve structural differences in the upper crust but adequate to reveal a moderately good conductor at upper mantle/lower crustal depths in the Caledonian metamorphic zone. In contrast the whole of the crust in the Lewisian Foreland is highly resistive and there is no evidence of an intermediate conducting layer between the crust and mantle in this region.

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Palaeomagnetism of Late Precambrian or Cambrian diorites from Leicestershire, U.K.

Cited by 6 publications

References 7 publications

A palaeomagnetic study of the Charnian, Caldecote, and Uriconian volcanics and plutons, central England

A palaeomagnetic study of the Charnian, Caldecote, and Uriconian volcanics and plutons, central England

The palaeomagnetism of Jersey volcanics and dykes, and the Lower Palaeozoic apparent polar wander path for Europe

Palaeomagnetism of late Precambrian-Cambrian volcanics and intrusives from the Armorican Massif, France

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