The petrogenesis of the Early Permian Variscan granites of the Cornubian Batholith: Lower plate post-collisional peraluminous magmatism in the Rhenohercynian Zone of SW England

Simons, Beth; Shail, RK; Andersen, Jens C.Ø.

doi:10.1016/j.lithos.2016.05.010

Cited by 72 publications

(75 citation statements)

References 103 publications

(150 reference statements)

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“…clear trends exist in the Lee Moor samples. All samples display similar major element chemistry to previous studies (e.g., Charoy, 1986;Chappell & Hine, 2006;Simons et al, 2016). Blackenstone BG represent the least evolved of the studied granites, with the lowest SiO 2 , Al 2 O 3 and LOI as well as the highest MgO, FeO, TiO 2 and CaO); this geochemical signature is similar to that reported by Stone (1992; Figure 4b).…”

Section: Accepted Manuscriptsupporting

confidence: 86%

“…As Figure 4 shows the BG at Crownhill has slightly more evolved compositions than the Blackenstone BG, with higher SiO 2 , K 2 O and lower incompatible elements. Biotite granites consistently plot above the zirconium saturation threshold for peraluminous granites at 750°C (>100 ppm) of Watson & Harrison (1983), indicating that saturation concentrations are greater in the BGs (Chappell & Hine, 2006;Simons et al, 2016). Crownhill BG show identical REE trends to the Blackstone BG, which comprises the largest ΣREE contents, the shallowest Eu anomaly (0.54 ± 0.10) and lowest Gd/Yb CN ratio (1.28).…”

Section: Accepted Manuscriptmentioning

confidence: 89%

“…The batholith displays considerably textural and mineralogical variation (e.g., Dangerfield & Hawkes, 1981;Simons et al, 2016;Figure 1). A crustal origin for the granites has been proposed (e.g., Exley & Stone 1982;Jackson et al, 1989;Chappell & Hine, 2006;Simons et al, 2016Simons et al, , 2017, where a feldspathic metagreywacke is suggested as the protolith (Chappell & Hine, 2006;Simons et al, 2016).…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…The oldest granites (300-288 Ma) represent two-mica (e.g., Bodmin and Carnmenellis) and muscovite granites (e.g., Hemerdon and Carn Brea; Figure 2), whereas the younger granites (284-274 Ma) are o posed of o posite iotite a d tour ali e gra ites e.g., Dart oor, "t. Austell a d La d s E d . Simons et al (2016) propose a two-stage emplacement model, where the older granites formed through muscovite dehydration melting (731-806°C, >5 kbar), induced by magmatic underplating during ongoing convergence. Increasing temperatures and declining pressures in the lower crust resulted in the melting of more refractory minerals and biotite (770-850°C, 4 kbar), producing the later biotite-dominated granites, which fractionated to produce tourmaline granites.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

“…Peraluminous granites [Al 2 O 3 > (Na 2 O+K 2 O+CaO)] occur in orogens across the world (e.g., Sylvester, 1998;Yang et al, 2016), often hosting world-class magmatic and magmatic-hydrothermal ore deposits (Čer ŷ et al, 2005;Romer & Kroner, 2016). The Variscan granites of the Cornubian Batholith ( Figure 1) were emplaced during early Permian post-collisional extension (Shail & Wilkinson, 1994;Shail & Leveridge, 2009;Simons et al, 2016). Their diachronous emplacement has governed the distribution of tin-tungsten (Sn-W) mineralisation (Jackson et al, 1989;Chesley et al, 1993;Simons et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Zircon perspectives on the age and origin of evolved S-type granites from the Cornubian Batholith, Southwest England

Smith

Darling

Bullen³

et al. 2019

Lithos

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Granite stocks across southwest England have played a significant role in the genesis of world-class polymetallic mineralisation. This study presents the first geochemical and geochronological dataset for the composite Crownhill stock, placing it into the newly emerging geochronological framework for the Cornubian Batholith. The Crownhill stock comprises kaolinised two-mica granite in the north and variably-grained biotite granite in the south that encloses pods of tourmaline granite. All granites are peraluminous (A/CNK>1) and the biotite (BG) and tourmaline granites (TG) are related by the replacement of biotite by tourmaline and secondary muscovitization. Integrated LA-ICP-MS and CA-ID-TIMS geochronology indicate two-phase magmatism, where zircon cores yield 288.9 ± 5 Ma and 286.4 ± 5 Ma and rims yield 277.74 ± 0.33 Ma and 278.35 ± 0.35 Ma, for BG and TG respectively. The zircon cores crystallised during initial magmatism, that formed the two-mica and muscovite granites (e.g., Carnmenellis, Bodmin, and Hemerdon) exposed in the north of the Crownhill stock. The zircon rims crystallised from the second phase of magmatism the formed the biotite and tourmaline granites (e.g., Dartmoor and St. Austell). This indicates that zircon crystals were assimilated from older twomica and muscovite granites and entrained in the second phase of magmatism. Trace element compositions of zircon grains suggest that the rims crystallised from a more evolved magma, where zircon grains hosted in tourmaline granites are broadly more evolved than those from biotite granites. This is likely a result of elevated volatile concentrations delaying zircon fractionation. Trace cassiterite has been observed within interstitial tourmaline in the tourmaline granites, where crystallisation was likely induced by the removal of boron through tourmaline fractionation, coupled with the addition of Sn sourced from the alteration of biotite. The assimilation and over-printing of older granites by second-stage magmatism suggests that the initial phase of magmatism could be more widespread than initially thought and that tourmalinisation may have been responsible for leaching and remobilising Sn from the biotite-rich granites.

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Section: Accepted Manuscriptsupporting

confidence: 86%