A5020021639- Geological and Geochemical Analysis
- earthquake and tectonic studies
- Geochemistry and Geologic Mapping
- High-pressure geophysics and materials
- Geology and Paleoclimatology Research
- Paleontology and Stratigraphy of Fossils
- Astro and Planetary Science
- Planetary Science and Exploration
- Geological and Geophysical Studies
- Geological formations and processes
- Geomagnetism and Paleomagnetism Studies
- Geochemistry and Elemental Analysis
- Geological Studies and Exploration
- Hydrocarbon exploration and reservoir analysis
- Drilling and Well Engineering
- Mineralogy and Gemology Studies
- Geophysical and Geoelectrical Methods
- Seismic Imaging and Inversion Techniques
- Paleontology and Evolutionary Biology
- Geological Modeling and Analysis
- Geological and Geophysical Studies Worldwide
- Methane Hydrates and Related Phenomena
- Isotope Analysis in Ecology
- Mineral Processing and Grinding
- Global Maritime and Colonial Histories
University of the Witwatersrand
2015-2024
Academy of Science of South Africa
2020
University of the Western Cape
2020
World Health Organization
2020
Stellenbosch University
2020
UNESCO
2020
University of South Africa
2020
University of Pretoria
2020
Government of Newfoundland and Labrador
2015
University of Toronto
2015
Significance Since the Pangea supercontinent formed about 320 million years ago, plumes that sourced large igneous provinces and kimberlites have been derived from edges of two stable thermochemical reservoirs at core–mantle boundary. We test whether it is possible to maintain this remarkable surface-to-deep Earth correlation before through development a new plate reconstruction method find our reconstructions for past 540 comply with known geological tectonic constraints (opening closure...
New U‐Pb zircon ages and Sm‐Nd Rb‐Sr isotopic data are presented for orthogneisses from north‐central Madagascar, including Île Sainte Marie, Alaotra‐Beforona, Maevatanana, Ambatolampy‐Ambatomarina. A migmatite tonalite gneiss Marie is dated precisely at $$3187\pm 2$$ Ma has a model age (TDM) of 3204 Ma, thereby establishing Middle Archean the oldest, juvenile gneisses in northeast Madagascar. Dated orthogneisses, intrusive into schist/paragneiss sequences, range between 2522 2494 have 3207...
The Seychelles islands consist of undeformed and unmetamorphosed, metaluminous monzogranites granodiorites Neoproterozoic age (∼750 Ma). Subsolvus, lesser hypersolvus granitoids are crosscut by coeval dolerite dykes, dominantly olivine tholeiite composition. Field relations suggest that mixing between granitoid doleritic magmas generated a variety minor intermediate rocks occur as irregular masses enclaves; their compositions plot linear arrays those dolerites granitoids. Two groups can be...
The compositions, textures, associated rocks and tectonic environments of anorthosites allow categorization into six different types, some which show distinct age-restrictions in terrestrial planetary history. Primordial, Archean Proterozoic are distinctly restricted time space. Those layered mafic intrusions ophiolites no apparent time-restrictions. Primordial form the bulk lunar crust possibly that Mercury, probably formed response to accretion. No surviving this nature has yet been found...
Significance The Iceland hotspot is widely thought to be the surface expression of a deep mantle plume from core–mantle boundary that can traced back in time at least 62 My. However, some lavas contain continental material, which has previously been proposed have recycled through plume. Here, we argue split off sliver continent Greenland Early Eocene. This now located beneath southeast where it locally contaminates plume-derived magmas.
Kevin Burke’s original and thought-provoking contributions have been published steadily for the past 60 years, more than a decade ago he set out to resolve how plate tectonics mantle plumes interact by proposing simple conceptual model, which we will refer as Burkian Earth. On Earth, take us from deepest sub-lithospheric depths, where partial melting occurs, surface, hotspot lavas erupt today, large igneous provinces kimberlites erupted episodically in past. The arrival of plume head...
Research Article| April 01, 1999 Neoproterozoic continental arc magmatism in west-central Madagascar Michael J. Handke; Handke 1Department of Earth and Planetary Sciences, Washington University, St. Louis, Missouri 63130-4899, USA Search for other works by this author on: GSW Google Scholar Robert D. Tucker; Tucker Lewis Ashwal 2Department Geology, Rand Afrikaans Auckland Park, 2006, South Africa Author Article Information Publisher: Geological Society America First Online: 02 Jun 2017...
A U–Pb zircon age of 91.2 ± 0.2 Myr from western India (St. Mary islands) confidently links with the Late Cretaceous magmatic province in Madagascar (≈ 84–92 Ma), and is within analytical error Analalava gabbro pluton (91.6 0.3 Myr) northeastern Madagascar. Palaeomagnetic data allow us to postulate a new India–Madagascar fit (Euler latitude = 14.24°, longitude 38.8° rotation angle –69.2°). This applicable Cretaceous, directly prior during early phase Madagascar–India separation. In our...
Research Article| May 01, 2003 New way to map old sutures using deformed alkaline rocks and carbonatites Kevin Burke; Burke 1School of Geosciences, University the Witwatersrand, Private Bag 3, Witwatersrand 2050, South Africa Search for other works by this author on: GSW Google Scholar Lewis D. Ashwal; Ashwal Susan J. Webb Author Article Information Publisher: Geological Society America Received: 29 Oct 2002 Revision 06 Jan Accepted: 08 First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print...
Two‐stage diapiric models for lunar ferroan anorthosites and terrestrial massif are examined. The model is developed to explain early differentiation in the absence of a magma ocean. If correct, serves as an analog development anorthositic diapirs. There field textural evidence transport mostly crystalline material within complexes. This evidence, combined with lavas phase equilibrium constraints inhibiting production hyperaluminous magmas, consistent detachment plagioclase‐rich mushes from...
Research Article| September 01, 2005 Magmatic stratigraphy in the Bushveld Northern Lobe: continuous geophysical and mineralogical data from 2950 m Bellevue drillcore Lewis D. Ashwal; Ashwal School of Geosciences, University Witwatersrand, Private Bag 3, WITS, 2050, RSA., e-mail: ashwall@geosciences.wits.ac.za Search for other works by this author on: GSW Google Scholar Susan J. Webb; Webb webbs@geosciences.wits.ac.za Michael W. Knoper Department Geology, Johannesburg, P.O. Box 524, Auckland...
Peninsular India was assembled into a continental block c. 3 million km 2 in area as result of collisions throughout the length 4000 long S-shaped mountain belt that first recognized from continuity strike highly deformed Proterozoic granulites and gneisses. More recently recognition variety tectonic indicators, including occurrences ophiolitic slivers, Andean-margin type rocks, collisional rift foreland basin, well many structural isotopic age studies have helped to clarify history this...