Direct Mesoproterozoic connection of the Congo and Kalahari cratons in proto-Africa: Strange attractors across supercontinental cycles

Abstract

Mobilistic plate-tectonic interpretation of Precambrian orogens requires that two conjoined crustal blocks may derive from distant portions of the globe. Nonetheless, many proposed Precambrian cratonic juxtapositions are broadly similar to those of younger times (socalled "strange attractors"), raising the specter of bias in their construction. We evaluated the possibility that the Congo and Kalahari cratons (Africa) were joined together prior to their amalgamation along the Damara-Lufilian-Zambezi orogen in Cambrian time by studying diabase dikes of the Huila-Epembe swarm and sills in the southern part of the Congo craton in Angola and in Namibia. We present geologic, U-Pb geochronologic, and paleomagnetic evidence showing that these two cratons were directly juxtaposed at ca. 1.1 Ga, but in a slightly modified relative orientation compared to today. Recurring persistence in cratonic connections, with slight variations from one supercontinent to the next, may signify a style of supercontinental transition similar to the northward motion of Gondwana fragments across the Tethys-Indian oceanic tract, reuniting in Eurasia.

Large Igneous Provinces (LIPs) and Anoxia Events in “The Boring Billion”

“…Other mafic magmatic events during this period include the Rincon del Tigre-Huanchaca dolerite sills (dykes) with baddeleyite U-Pb ages of 1,112 ± 2 Ma to 1,110 ± 2 Ma in Amazonia (Teixeira et al, 2015b), the Epembe-Huila Angola gabbro-norite dykes in Congo (baddeleyite U-Pb age of 1,110 ± 3 Ma, Ernst et al, 2013b;1,127 ± 8 Ma to ca. 1,104 Ma;Salminen et al, 2018) and the 1,113 ± 7 Ma (zircon U-Pb age) Mahoba mafic dyke in India (Pradhan et al, 2012). Of similar, but not exactly the same age is the SW Laurentia magmatic province, which consists of diabase sills (dykes) with baddeleyite U-Pb ages from 1,094 ± 2 Ma to 1,080 ± 3 Ma (Bright et al, 2014 (Peng et al, 2011a(Peng et al, , 2011bZhang et al, 2016b).…”

Recording the largest gabbro-anorthositic complex worldwide: The Kunene Complex (KC), SW Angola

“…Large-scale calc-alkaline plutonic masses and scarce metasedimentary sequences of Palaeoproterozoic age are dominant in the area (Carvalho, 1982;Kröner et al, 2010Kröner et al, , 2015McCourt et al, 2013;Pereira et al, 2013aPereira et al, , 2013bJelsma et al, 2018). This crystalline basement was intruded during the Mesoproterozoic by a set of mafic dykes of 1.50 and 1.10 Ga (Ernst et al, 2013;Salminen et al, 2018), and by the large Kunene Complex (1438-1375 Ma; e.g., Mayer et al, 2004;Drüppel et al, 2007;Baxe, 2007;Bybee et al, 2019).…”

“…Distinct Mesoproterozoic mafic intraplate events have been recorded in SW Angola, between 1502 ± 5 Ma (obtained in a dolerite sill intruding into the Chela Group in the Humpata region), 1200 Ma (K-Ar dating in NW-SEtrending dolerite dykes or subhorizontal sills from the Oncocua region; Silva et al, 1973;Carvalho et al, 2000) and 1110 ± 3 Ma (in a gabbronorite dyke below the Chela Group, related to the N-S-trending family of dyke swarms of southern Angola), interpreted as part of the plumbing system of LIPs (Ernst et al, 2013;Salminen et al, 2018). The intrusion of these dolerite dykes probably took place all over Angola favoured by regional fracturing and reactivation of older structures (Andrade, 1962).…”