Terrane

About: Terrane is a research topic. Over the lifetime, 11025 publications have been published within this topic receiving 442596 citations. The topic is also known as: tectonostratigraphic terrane.

The African upper mantle and its relationship to tectonics and surface geology

Abstract: This paper focuses on the upper-mantle velocity structure of the African continent and its relationship to the surface geology. The distribution of seismographs and earthquakes providing seismograms for this study results in good fundamental and higher mode path coverage by a large number of relatively short propagation paths, allowing us to image the SV-wave speed structure, with a horizontal resolution of several hundred kilometres and a vertical resolution of similar to 50 km, to a depth of about 400 km. The difference in mantle structure between the Archean and Pan-African terranes is apparent in our African upper-mantle shear wave model. High-velocity (4-7 per cent) roots exist beneath the cratons. Below the West African, Congo and Tanzanian Cratons, these extend to 225-250 km depth, but beneath the Kalahari Craton, the high wave speed root extends to only similar to 170 km. With the exception of the Damara Belt that separates the Congo and Kalahari Cratons, any high-speed upper-mantle lid below the Pan-African terranes is too thin to be resolved by our long-period surface wave technique. The Damara Belt is underlain by higher wave speeds, similar to those observed beneath the Kalahari Craton. Extremely low SV-wave speeds occur to the bottom of our model beneath the Afar region. The temperature of the African upper mantle is determined from the SV-wave speed model. Large temperature variations occur at 125 km depth with low temperatures beneath west Africa and all of southern Africa and warm mantle beneath the Pan-African terrane of northern Africa. At 175 km depth, cool upper mantle occurs below the West African, Congo, Tanzanian and Kalahari Cratons and anomalously warm mantle occurs below a zone in northcentral Africa and beneath the region surrounding the Red Sea. All of the African volcanic centres are located above regions of warm upper mantle. The temperature profiles were fit to a geotherm to determine the thickness of the African lithosphere. Thick lithosphere exists beneath all of the cratonic areas; independent evidence for this thick lithosphere comes from the locations of diamondiferous kimberlites. Almost all diamond locations occur where the lithosphere is 175-200 km thick, but they are largely absent from the regions of the thickest lithosphere. The lithosphere is thin beneath the Pan-African terranes of northern Africa but appears to be thicker beneath the Pan-African Damara Belt in southern Africa.

A Pan‐African granulite facies metamorphic episode in Prydz Bay, Antarctica: Evidence from Sm‐Nd garnet dating

Abstract: The granulite facies gneisses along the Prydz Bay coastline, Antarctica, have long been regarded as part of an extensive Proterozoic (ca 1000 Ma) terrane, based on correlations with other parts of eastern Antarctica. New Sm‐Nd garnet‐whole rock dates for various rocks indicate that the main metamorphic episode that has affected the rocks in Prydz Bay is of Pan‐African age (515–490 Ma). Only in one locality, in the western part of the area, have older garnet ages been found. On Sostrene Island, where petrographic and analytical work suggests an earlier higher pressure metamorphic event, an age of 990 Ma correlates with some well‐established metamorphic ages from the Northern Prince Charles Mountains to the south, the Rayner Complex, Enderby Land to the southwest and part of the Rauer Group to the east. Evidence for reworking of the rocks on Sostrene is provided by the textures and by the 500 Ma ages which have been determined for interlayered pelitic and felsic gneisses. The notion of a continuous Late Pro...

Jurassic tectonic history of the Otago Schist, New Zealand

Abstract: A regional reanalysis of the Otago Schist shows that ductile mesoscopic structures can be interpreted as elements of a single, progressive, heterogeneous, noncoaxial, Jurassic deformation related to juxtaposition of the Caples and Torlesse terranes. Stretching lineations are parallel, oblique, and perpendicular to the orogen in various parts of Otago, but changes in trend are generally unrelated to the terrane boundary. Structural geometry and rare shear criteria indicate that the Caples terrane overthrust the Torlesse terrane from the south and west, but precise transport directions are not known, being model-dependent. Macroscopic recumbent folds may be present in the schist, but mainly in the form of partially developed nappe structures truncated by zones of retransposed foliation and/or high strain.

Tectonic evolution of Palaeozoic terranes in West Junggar, Xinjiang, NW China

Abstract: Nine separate Cambrian to Carboniferous terranes recognized in West Junggar, northwest China. They were amalgamated as part of the Central Asian Orogenic Belt which records accretion of continental, island-arc and oceanic terranes to Archaean-Proterozoic continental nuclei. Tangbale, Kekesayi, Ebinur and Mayila terranes (Cambrian-Silurian) evolved in intra-oceanic settings and docked, along a series of north-dipping subduction zones, on to the Laba terrane to their south. This southern continent was contiguous with lithosphere of the Kulumudi Ocean to the north. Devonian subduction on the northern edge of this ocean resulted in formation of a continental arc (Toli terrane) and accretionary complex (Kulumudi terrane). The Karamay terrane formed as an accretionary complex during the Carboniferous. The ophiolitic Sartuohai terrane was emplaced as melange between Kulumudi and Karamay terranes during the Late Carboniferous. Subduction migrated southward, continuing beneath these terranes, resulting in the intrusion of I-type granites into the Toli, Kulumudi, Sartuohai and Karamay terranes. These granites are closely associated with epithermal and porphyry-style gold mineralization. Composite terranes either side of the Kulumudi Ocean collided in the Late Carboniferous, marking the final consolidation of Central Asia. Collision was accompanied by anorogenic granite and diabase dyke intrusion, followed by widespread latest Carboniferous to Permian extension, and subsequently the formation of the Junggar Basin. West Junggar has been further disrupted by Cenozoic strike-slip faulting along Junggar and Dalabute faults.

Paleomagnetic constraints on the Mesozoic drift of the Lhasa terrane (Tibet) from Gondwana to Eurasia

Abstract: The Mesozoic plate tectonic history of Gondwana-derived crustal blocks of the Tibetan Plateau is hotly debated, but so far, paleomagnetic constraints quantifying their paleolatitude drift history remain sparse. Here, we compile existing data published mainly in Chinese literature and provide a new, high-quality, well-dated paleomagnetic pole from the ca. 180 Ma Sangri Group volcanic rocks of the Lhasa terrane that yields a paleolatitude of 3.7°S ± 3.4°. This new pole confirms a trend in the data that suggests that Lhasa drifted away from Gondwana in Late Triassic time, instead of Permian time as widely perceived. A total northward drift of ∼4500 km between ca. 220 and ca. 130 Ma yields an average south-north plate motion rate of 5 cm/yr. Our results are consistent with either an Indian or an Australian provenance of Lhasa.