Some of the most important, rapid, and enigmatic changes in our Earth’s environment and biota occurred during the Neoproterozoic Era (1000540 million years ago; Ma). Paramount among these changes are the rapid evolution of eukaryotes and appearance of metazoa (Knoll 1992, Conway Morris 1993), major episodes of continental glaciation that may have extended to low latitudes (Hambrey & Harland 1985), marked increases in the oxygen concentration of the atmosphere and hydrosphere (Derry et al 1992), the reappearance of sedimentary banded iron formations (BIF; James 1983), and striking temporal variations in the isotopic composition of C and Sr (Asmerom et al 1991, Derry et al 1992). Understanding the causes of and relationships between these changes is a challenging focus of interdisciplinary research, and there are compelling indications that the most important causes were tectonic (Des Marais et al 1992, Veevers 1990). For example, development of ocean basins may have been accompanied by the development of seafloor hydrothermal systems, which lowered the 87Sr/S6Sr of seawater, led to the development of BIF, and formed anoxic basins where organic carbon could be buried, thus leading to an increase in O~. Continental collision and formation of a supercontinent may have led to continental glaciation and an increase in the 87Sr/86Sr of seawater,

http://www.utdallas.edu/~rjstern/egypt/PDFs/General/SternEAO-AREPS94.pdf

ARC Assembly and Continental Collision in the Neoproterozoic East African Orogen: Implications for the Consolidation of Gondwanaland

A synopsis of events related to the assembly of eastern Gondwana

https://www.adelaide.edu.au/directory/alan.collins?dsn=directory.file;field=data;id=2241;m=view

Amalgamating eastern Gondwana: The evolution of the Circum-Indian Orogens

Linking accretionary orogenesis with supercontinent assembly

The East African–Antarctic orogen is one of the largest orogenic
belts on the planet. It resulted from the collision of various parts of
proto–East and West Gondwana during late Neoproterozoic–early
Paleozoic time (between 650 and 500 Ma). We propose that the
southern part of this Himalayan-type orogen can be interpreted in
terms of a lateral-escape tectonic model. Modern Gondwana reconstructions
show that the southern part of the East African–
Antarctic orogen can best be reassembled when a number of microplates
(the Falkland, Ellsworth-Haag, and Filchner blocks) are
positioned between southern Africa and East Antarctica. This microplate
assemblage is unusual. The microplates probably represent
shear-zone–bounded blocks, produced by tectonic translation
during lateral escape, similar to those currently evolving in Southeast
Asia. One of the escape-related shear zones is exposed as the
20-km-wide Heimefront transpression zone in western Dronning
Maud Land. Coats Land, a crustal block within the orogen, probably
represents a block of older crust that was not subjected to
tectonometamorphic reworking ca. 500 Ma by lateral tectonic escape.
The southern part of the orogen is also typified by very large
volumes of late-tectonic A2-type granitoids, intruded ca. 530–490
Ma, probably as a consequence of delamination of the orogenic
root and the subsequent influx of hot asthenospheric mantle during
tectonic escape. Erosional unroofing of the orogen is documented
by the remnants of originally massive areas covered by Cambrian–
Ordovician molasse-type sedimentary rocks throughout Africa,
Arabia, and Antarctica, testifying to the past extent and size of this
largest of orogens.

Himalayan-type indenter-escape tectonics model for the southern part of the late Neoproterozoic–early Paleozoic East African– Antarctic orogen

Two new U-Pb concordia zircon ages are reported for granulite-facies rocks from the Mozambique Orogenic Belt in eastern Tanzania. These rocks are thought to have been generated during collision-related crustal thickening process and exhumed by deep erosion. A two-pyroxene granulite sample from the Pare Mountains has yielded a concordia upper intercept age of 645 ± 10 Ma, whereas a granulite-facies meta-anorthosite sample from the Uluguru Mountains has given an upper intercept age of 695 ± 4 Ma. Evidence for the involvement of older crustal material (pre-Late Proterozoic) was not found. These zircon data indicate crystallization during the peak of granulite-facies metamorphism during the Pan-African orogeny ( c . 950 to c . 550 Ma) consistent with a subduction-collisional environment.

S. Muhongo

Papers

Pan-African granulite-facies metamorphism in the Mozambique Belt of Tanzania: U-Pb zircon geochronology