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.

Geotectonic subdivision and areal extent of the Sangun belt, Inner Zone of Southwest Japan

Abstract: The Sangun belt has long been considered to be a major coherent glaucophanitic terrane of Permian to Triassic age, and to be paired with the low-P/T Hida belt to the north. However, recent progress in geochronology, metamorphic geology, and tectonics has revealed that the belt is in fact comprised of two geologic units of different ages and with contrasting conditions of formation. The older unit is named the Renge belt and the younger the Suo belt. The Renge belt is the oldest of the high-P/T metamorphic belts in the Japanese Islands and extends from northern Kyushu, through the San-in coastal regions, to the Hida marginal belt. It is characterized by 330–280 Ma ages and the association of glaucophane–schist to epidote–amphibolite facies schists. The Renge belt is also typically associated with meta–ophiolite sequences (470–340 Ma) including serpentinite. The Suo belt is characterized by 230–160 Ma high-P/T schists closely related to weakly metamorphosed Permian accretionary rocks of the Akiyoshi belt. Metamorphic facies series is from the prehnite–pumpellyite facies through the pumpellyite–actinolite and glaucophane–schist facies to the epidote–amphibolite facies. The belt is widespread in west Kinki to north and central Kyushu via Chugoku, but also stretches further to the southwest and is present in the Ishigaki-Iriomote Islands of the southern Ryukyu Arc. Throughout this belt, there are scattered small blocks or lenses of meta–ophiolite, whose K–Ar ages of relict hornblendes are 590 to 220 Ma. Bounded by low-angle faults and thrusts, both belts define subhorizontal nappes dipping gently north. The geotectonic framework in the Inner Zone of Southwest Japan is made up of, from north to south, the Hida-Oki, Renge, Akiyoshi, Suo, Maizuru plus ultra-Tamba, Mino-Tamba, and Ryoke belts, with a tectonically downward-younging polarity. This has resulted from stepwise accretions during Palaeozoic to Mesozoic time.

Mesozoic tectonics, North Island, New Zealand

Abstract: The Kawhia synclinorium along the western margin of North Island, New Zealand, is a relatively simple open structure with a subvertical to steeply east-dipping axial surface and contains a Triassic-Jurassic shelf or arc-trench gap sequence. It is bounded to the east by a narrow zone of serpentinite and ultramafic rock corresponding to the magnetic Junction anomaly. In the Waipapa and Torlesse terranes east of the Junction anomaly, three deformation phases can be recognized: (1) formation of melange and imbrication of strata, with fold axes trending across the now-dominant basement grain and fold vergence predominantly toward the south; (2) strongly asymmetric folding and imbrication and further melange formation on horizontal axes parallel to the present structural grain; folds verge to the east, and beds in the axial ranges have rotated to vertical and overturned attitudes; and (3) open folding on steeply plunging axes. Phases 1 and 2 are part of the Early Cretaceous Rangitata orogeny or predate it. There is no evidence yet for the age of phase 3 structures. It is hypothesized that the rocks of the Waipapa and Torlesse terranes were imbricated and accreted in a suture zone east of the Junction anomaly. Phase 1 structures were formed oblique to the trend of the New Zealand geosyncline because of a strike-slip component of movement transmitted to the sedimentary column only before and during early decollement. Age patterns in the Torlesse and Waipapa terranes indicate that simultaneously with accretion the clastic apron prograded from south to north.

Northward translation of “BAJA British Columbia” along the Late Cretaceous to Paleocene margin of western North America

Abstract: Paleomagnetic data suggest that a large part of British Columbia and southern Alaska was at the latitude of Baja California, Mexico, in early Late Cretaceous time. This allochthonous block (Baja BC) includes the Insular (Talkeetna in Alaska) and Intermontane composite terranes, the miniterranes between them, and possibly part of the Omineca metamorphic belt. Assuming that Baja BC was adjacent to North America by middle Cretaceous, an analysis using plate kinematics of the Pacific basin produces a model of northward movement of Baja BC which is compatible with the known geology of the reconstructed margin of western North America. Baja BC moved north 2400 km as part of the KuIa plate along a transform margin with North America from 85 to 66 Ma. This time interval is marked by the cessation of igneous activity in the Sierra Nevada, development of wrench faults and basins along coastal California, and initiation of Laramide-style tectonics to the east. Within Baja BC, diminished igneous activity to the west was coeval with possible wrench-tectonic basins along its eastern margin. By the end of the Cretaceous, Baja BC was positioned from Oregon to northern British Columbia. Between 66 and 56 Ma, Baja BC became attached to North America in a dextral-transpressive stage, during which the Kula--North America plate boundary expanded to encompass the whole block with a series of northwest trending strike-slip faults, a fold and thrust belt in the east, and large-scale uplifts and the formation of an incipient volcanic arc on the west. Southern Alaska was the site of convergence during the whole of the period of northward translation of Baja BC. A Late Cretaceous subduction zone in Alaska evolved into a major compressional belt as the basin and miniterranes on the northern margin of Baja BC collided with interior Alaska. The collision culminated in the Paleocene with formation of the McKinley granites and coeval dextral slip on the Denali fault system.

Review of the Proterozoic evolution of the Grenville Province, its Adirondack outlier, and the Mesoproterozoic inliers of the Appalachians

Abstract: In recent years, a rapidly expanding database, especially in sensitive high-resolution ion microprobe (SHRIMP) geochronology, has led to signifi cant advances in understanding of the Precambrian tectonic evolution of the Grenville Province, including its Adirondack outlier, and the Mesoproterozoic inliers of the Appalachians. Based upon this information, we review the geochronology and tectonic evolution of these regions and signifi cant similarities and differences between them. Isotopic data, including Pb isotopic mapping, suggest that a complex belt of marginal arcs and orogens existed from Labrador through the Adirondacks, the midcontinent, and into the southwest during the interval ca. 1.8‐1.3 Ga. Other data indicate that Mesoproterozoic inliers of the Appalachians, extending from Vermont to at least as far south as the New Jersey Highlands, are, in part, similar in composition and age to rocks in the southwestern Grenville Province. Mesoproterozoic inliers of the Appalachian Blue Ridge likewise contain some lithologies similar to northern terranes but exhibit Nd and Pb isotopic characteristics suggesting nonLaurentian, and perhaps Amazonian, affi nities. Models invoking an oblique collision of eastern Laurentia with Amazonia are consistent with paleomagnetic results, and collision is inferred to have begun at ca. 1.2 Ga. The collision resulted in both the ca. 1190‐1140 Ma Shawinigan orogeny and the ca. 1090‐980 Ma Grenvillian orogeny, which are well represented in the Appalachians. Several investigators have proposed that some Amazonian Mesoproterozoic crust may have been tectonically transferred to Laurentia at ca. 1.2 Ga. Data that potentially support or contradict this model are presented.