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您的检索式：作者名="Valby van Schijndel"
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| 1 | Evidence for Mesoproterozoic collision,deep burial and rapid exhumation of garbenschiefer in the Namaqua Front,South Africa显示文摘Metamorphic provinces such as the^1 Ga Grenvillian,~400 Ma Caledonide and Triassic Qinling Provinces often contain rocks with high-pressure assemblages such as eclogites,which formed at mantle depths in subduction zones.These are evidence of the accretion of terranes by subduction of oceans and collision to form large tectonostratigraphic provinces.The Mesoproterozoic Namaqua-Natal Province comprises a number of terranes thought to have been assembled by plate-tectonic processes,but they have generally yielded metamorphic pressures below 5 kbar,corresponding to<20 km,crustal depths,lacking evidence for subduction processes.The Kaaien Terrane in the Namaqua Front contains two large garbenschiefer units with the unusual paragenesis garnet-hornblende-epidote-white mica-plagioclase-ilmenite-quartz.Their protoliths are graywackes influenced by andesitic volcanism during their deposition at^1870 Ma,in a passive margin of the Rehoboth Province or Kaapvaal Craton.Prograde garnet growth dated at 11655 Ma culminated in peak metamorphic conditions of 64530C and 10.40.7 kbar,corresponding to 40 km depth.This is attributed to subduction of these rocks before collision between the overriding arc-related Areachap Terrane,the Kaaien Terrane and the Kaapvaal-Rehoboth cratonic block during the Namaqua orogeny.Exhumation of the garbenschiefer slabs was followed by rapid cooling,as the 11435 Ma argon dates of hornblende and white mica,with closure temperatures^540C and^440C respectively,are the same within error.This was probably due to tectonic juxtaposition of the garbenschiefer slab with much cooler rock units.The exhumation was accommodated along the Trooilapspan-Brakbosch Shear Zone due to ongoing transpression.Other components of the Namaqua Front have distinctly different P-T-t paths,exemplified by greenschist metamorphism in the 1300 Ma Wilgenhoutsdrift Group,and medium-pressure metamorphism in the Areachap Terrane.They were juxtaposed by late-tectonic uplift and transpressional movements.The^40 km depth of garbenschiefer peak metamorphism is the deepest yet found in the Namaqua-Natal Province and strengthens the plate tectonic model of accretion by collision of terranes at the end of a Wilson cycle.The high pressure paragenesis of the garbenschiefer was preserved due to its location in the Namaqua Front,whereas most other parts of the Namaqua-Natal Province were overprinted by 1100–1020 Ma thermal events after the collision events. | Valby Van Schijndel David HCornell Robert Anczkiewicz Anders Schersten | 2020 | Geoscience Frontiers2020，11，2： | 2 |
| 2 | Reply to comment by S.H.Büttner on “Evidence for Mesoproterozoic collision,deep burial and rapid exhumation of garbenschiefer in the Namaqua Front,South Africa”显示文摘1.Introduction We thank Prof.Buttner for his comments on our paper(van Schijndel et al.,2020),which allow us to clarify our work and the tectonic model we proposed for the eastern margin of the Namaqua Sector of the Namaqua Natal Metamorphic Province.The Kaaien Terrane forms a tectonic transition between the Kaapvaal Craton,Rehoboth Province,Kheis belt and the Archeachap Terrane of the Namaqua Sector and forms part of a NW-vergent foreland thrust sequence in the Namaqua Front(e.g.Cornell et al.,2006).The exact tectonic extent of the Kaaien Terrane is still unclear and it has recently been proposed to be part of the newly defined Kheis Terrane(Van Niekerk and Beukes,2019). | Valby van Schijndel David H.Cornell Robert Anczkiewicz Anders Schersten | 2020 | Geoscience Frontiers2020，11，5： | 0 |
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