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.

San Jacinto Fault Zone in the Peninsular Ranges of Southern California

Abstract: The San Jacinto fault zone is one of the major branches of the San Andreas fault system in Southern California. The straightness, continuity, and high seismicity of this zone, as well as its present right-lateral strain rate, suggest that currently it may be the most active member of the system in this region. Both intrusive rocks of the mid-Cretaceous Southern California batholith and prebatholithic metasedimentary and possibly metavolcanic rocks are exposed nearly continuously along a 50-mile segment of the fault zone between San Jacinto and Borrego valleys in the northeastern Peninsular Ranges. The prebatholithic terrane on both sides of the fault zone in this interval consists of locally migmatized banded gneiss and lesser amounts of amphibolite, quartzite, marble, schist, and metaconglomerate. These rocks, together with gabbroic, tonalitic, granodioritic, and adamellitic plutons, constitute distinctive sequences of generally steep-walled bodies which are offset right-laterally by the various breaks in the fault zone. A marker section of relatively marble-rich metamorphic rocks within and parallel to a regionally unique, moderately dipping, postbatholithic zone of cataclastic deformation is also offset near Borrego and Clark valleys. Extrapolation of critical offset contacts indicates that the cumulative right-lateral movement across the San Jacinto fault zone is about 15 miles. The southwestern side of the fault zone has been relatively raised through a probable 1- to 2-mile vertical component of net displacement, although the San Jacinto and Santa Rosa mountains northeast of the zone are now topographically higher. North of Anza, distinctive Pleistocene gravels are offset at least 3.2 miles, and stream courses have been displaced 0.45 mile in a right-lateral sense. The magnitude of displacement and its distribution among the various breaks within the zone indicate that: (1) the San Jacinto fault may connect with the Imperial fault in central Imperial Valley; (2) the positions of the Banning and Sierra Madre faults along the southern margins of the San Bernardino and San Gabriel mountains may reflect the total movement of the San Jacinto fault; (3) if the displacement on the San Andreas fault zone is as large as 160 miles, the San Jacinto fault has not always been as important a member of the larger system as its current activity suggests; and (4) when compared to the minimum probable Quaternary faulting rate, the displacement suggests the San Jacinto fault zone might be as young as Pliocene.

Crustal structure of the Grenville front and adjacent terranes

Abstract: Under the auspices of the Great Lakes International Multidisciplinary Program on Crustal Evolution, approximately 320 km of deep seismic reflection data were collected in Lake Huron along a profile that extends east from the Manitoulin terrane across the Grenville front to the interior of the Grenville orogen. The Manitoulin terrane is characterized by a series of gently east-dipping reflections at about 20 km depth that separate a highly reflective lower crustal layer from a markedly less reflective upper layer. Imaged by strong reflections at the western end of a spectacular band of moderately east-dipping reflections, the Grenville front clearly truncates Manitoulin terrane structures to the west. These data are interpreted in terms of a speculative two-stage model involving (1) creation of a major decollement during northward collision of an allochthonous terrane with the southern Superior cratonic margin (1.83-1.89 Ga; Penokean orogeny) and (2) northwest-directed stacking of microterranes at the southeastern margin of the craton, followed by crust-penetrating ductile imbrication under high-pressure-high-temperature conditions leading to the ramping of deeply buried rocks to the near surface (1.0-1.3 Ga; Grenvillian orogeny).

Uranium‐lead zircon ages from the Median Tectonic Zone, New Zealand

Abstract: The Median Tectonic Zone (MTZ) of New Zealand is a generally north trending belt of Mesozoic subduction‐related I‐type plutonic, volcanic, and sedimentary rocks in South Island and Stewart Island that separates Permian strata of the Eastern Province Brook Street Terrane from lower to mid‐Paleozoic Gondwana margin assemblages of the Western Province. High‐precision isotope dilution U/Pb ages of zircons from 30 rocks are reported. Pre‐digestion leaching of zircon in hydrofluoric acid yielded significantly more concordant residues by removing common Pb and dissolving more soluble high‐U domains that have been more affected by relatively recent Pb loss. The results show that MTZ magmatism ranges in age from at least Early Triassic to Early Cretaceous (247–131 Ma), with a pronounced gap in the Middle Jurassic. Triassic plutons tend to occur on the eastern side of the MTZ, and they intrude volcanic/sedimentary sequences of the MTZ in Nelson and eastern Fiordland. These sequences are in turn intruded by...

Presence of Permian extension- and arc-type magmatism in southern Tibet: Paleogeographic implications

Abstract: The geographical location of the Lhasa terrane in the Permian remains a subject of debate. The recognition of the Permian basalts in the Tethyan Himalaya and the Permian volcanic rocks in the Lhasa terrane in southern Tibet together with the geochemistry of these rocks offer some new insights. The Permian basalts in the Tethyan Himalaya show a geochemical affi nity with tholeiitic continental fl ood basalts, and are interpreted to have formed in an extensional setting. The new geochemical data and the geographical distribution of these basalts indicate that they probably represent the easternmost extent of the Panjal continental fl ood basalt province. All of the Permian basalts in the Lhasa terrane show a calcalkaline , high-alumina basalt affi nity, with signifi cant negative Nb-Ta-Ti anomalies. These geochemical features, combined with the recent documentation of the Permian Songdo eclogite and sedimentological observations, indicate the existence of a subduction system beneath the central Lhasa subterrane in the Permian. The presence of both extension- and arc-type magmatism of Permian age in present-day southern Tibet is inconsistent with the general view that the Lhasa terrane did not rift away from the northern margin of the Greater India until the Late Permian or Triassic. Instead, we suggest that the central Lhasa subterrane may have been a microcontinent isolated in the Paleo-Tethyan Ocean basin, at least during the Carboniferous‐Middle Permian time.