Abstract During the Grenvillian assembly of Rodinia, the Namaqua-Natal Metamorphic Province (NNMP) was formed as a result of the convergence of the Laurentia and Kalahari cratons. A detailed model for this accretion along the south-eastern margin of the Kalahari Craton has been established, but the tectonic history of the NNMP along the western margin of the Kalahari Craton has remained highly controversial. U-Pb SHRIMP zircon age dating of gneiss in the Kakamas Domain of the NNMP, as well as U-Pb SHRIMP age dating of detrital zircons and 40Ar/39Ar dating of metamorphic muscovite from sediments overlying the gneiss, confirms the presence of at least two separate events during the Namaqua-Natal Orogeny at ~1 166 Ma and 1 116 Ma. These events occurred after the Areachap Terrane was accreted onto the western margin of the Proto-Kalahari Craton during the Kheis Orogeny. 40Ar/39Ar ages derived from metamorphic muscovite formed in the metasediments of the Kheis terrane does not provide evidence for the timing of the Kheis Orogeny but suggests that it most likely only occurred after ~1 300 Ma and not at 1 800 Ma as commonly accepted. A U-Pb concordia age of ~1 166 Ma was derived from granitic gneiss in the Kakamas Domain of the Bushmanland Subprovince, possibly reflecting subduction and the initiation of continent-continent collision between the Proto-Kalahari Craton and the Bushmanland Subprovince. This granitic gneiss is nonconformably overlain by the metasediments of the Korannaland Group that contains metamorphic muscovite with 40Ar/39Ar ages of ~1 116 Ma. This age suggest that complete closure of the ocean between the Proto-Kalahari Craton and Bushmanland Subprovince probably occurred about 50 Ma after the intrusion of the ~1 166 Ma granitic gneisses.

Rodinia

Orogeny

Laurentia

Geochronology

10.25131/sajg.123.0042

Cite

Citations (5)

Timing of weathering by 40Ar/39Ar dating of K-Mn oxides from Mary Valley, Gympie, Queensland

Yuexing Feng Paulo Vasconcelos

Source

Cite

Citations (2)

Animated reconstructions of the Late Cretaceous to Cenozoic northward migration of Australia, and implications for the generation of east Australian mafic magmatism

Geosphere (2017)

Isabelle Jones C. Verdel Tracey Crossingham Paulo Vasconcelos

Details of the Late Cretaceous–Cenozoic migration of the Australian continent have been sources of contention since the 1960s. Two types of apparent polar wander paths (APWPs) have emerged from previous paleomagnetic studies: one group based on sedimentary and lateritic data that includes relatively linear northward motion of Australia away from Antarctica, and a second group, based on basaltic and lateritic data, that includes significant longitudinal movement of the Australian continent. This study compares the migration and evolution of the Australian plate over the past 100 m.y. using these two competing paths. Our animated reconstructions illustrate the relative motion of the Australian plate, the formation of Cenozoic volcanic provinces in eastern Australia, the opening of the Coral and Tasman Seas, and the docking of the Ontong Java Plateau with the Solomon Islands. The reconstructions incorporate new 40Ar/39Ar and previously published geochronology data from Late Cretaceous to Cenozoic east Australian mafic to felsic volcanism in order to evaluate potential relationships between volcanism, changes in the motion of the Australian plate, and the opening of the Tasman and Coral Seas. We conclude that the APWP that includes significant longitudinal movement is more compatible than the linear path with both observable geological features (such as volcanic tracks) and the global moving hotspot reference frame. Our reconstructions reveal little correspondence between opening of the Tasman and Coral Seas and eruption of east Australian lava fields. However, the reconstructions and new 40Ar/39Ar geochronology illustrate that the formation of east Australian Late Cretaceous to Cenozoic central volcanoes and lava fields were closely linked, both temporally and spatially, and we suggest that edge-driven convection was an important process in the generation of both types of east Australian volcanic provinces.

Geochronology

Apparent polar wander

10.1130/ges01405.1

Cite

Citations (22)

40Ar/39Ar constraints on pervasive supergene manganese mineralization of the late Cenozoic age throughout South China

Bulletin of Mineralogy Petrology and Geochemistry (2008)

Jianwei Li Dai-Rong Yan Xiao-Dong Deng Lei Chen Paulo Vasconcelos

Supergerne Mn-oxide deposits are widely distributed in Guangxi, Guangdong, Hunan, and Fujian Provinces of southern China and represent the second most important Mn ore types, following the sedimentary Mn-carbonate deposits in China. However, knowledge on the timing of supergene Mn enrichment is very limited due to lack of radiometric dating methods that are applicable to this type of deposit. In the last few years, the authors have performed a comprehensive geochronological study of supergene Mn-oxide deposits by using the Ar/Ar method. Incremental heating analysis of around 110 mineral separates of K-bearing Mn-oxides yielded reliable plateau ages that range from 23.64 ± 0.29 Ma and 0.48 ± 0.17 Ma (2σ). The age data thus indicate that pervasive supergene Mn enrichment in South China commenced at least in the latest Oligocene and persisted into the present time. Given the fact that the uppermost parts of most Mn-oxide deposits have been removed or destroyed by later denudation and/or mining, the supergene mineralization event may date back to early Oligocene or even the Eocene. The age distribution of supergene Mn-oxide deposits in South China shows a spatial trend, with the youngest ages recorded in the west, whereas the oldest ages were preserved in the east. This reflects how tectonic stability has affected the preservation of weathering profiles and Mn-oxides deposits therein. The results from this study also demonstrate that formation of an industrial supergene Mn-oxide deposit may have spanned tens of million years, in great contrast with most hydrothermal deposits that may be formed in only 10s to 100s thousand years. The approaches and procedures employed in this study can be used in the study of geochronology of other weathering-related ore deposits such as lateritic gold and nickel deposits.

Supergene (geology)

Denudation

Source

Cite

Citations (1)

40Ar/39Ar geochronology of the Fernando de Noronha Archipelago and implications for the origin of alkaline volcanism in the NE Brazil

Journal of Volcanology and Geothermal Research (2012)

Gabriela Perlingeiro Paulo Vasconcelos K. M. Knesel D. S. Thiede Umberto G. Cordani

Archipelago

Geochronology

Chronology

K–Ar dating

10.1016/j.jvolgeores.2012.08.017

Cite

Citations (41)