Amalgamation Of Crustal Blocks Research Articles

Late Paleoproterozoic ultrahigh-temperature metamorphism in the Korean Peninsula

The Paleoproterozoic rock record from the Sino-Korean Peninsula was fundamental to the models on evolution of the Asian continental collage and its relationship with the amalgamation and disruption of Proterozoic supercontinents such as Columbia and Rodinia. In this study, we present results from a comprehensive investigation on the khondalites in the Hongseong area, along the western part of the Gyeonggi massif within the central Korean Peninsula involving petrography, phase equilibria forward modeling, and zircon U-Pb geochronology, REE geochemistry and Lu – Hf isotopes. The P-T pseudosections show that the peak mineral assemblage of garnet + sillimanite + quartz + plagioclase + K-feldspar + ilmenite in the khondalite is stable at 7.5–9.6 kbar and 895–990 °C, corresponding to ultra-high temperature (UHT) metamorphism. We also report the first finding of corundum and quartz inclusions within sillimanite enclosed in garnet porphyroblast further confirming UHT metamorphism. The interpreted P-T path involves decompression and exhumation along a clockwise trajectory as suggested by the retrograde textures and mineral phase equilibria modeling.The detrital zircon U – Pb data from the khondalite show multiple age peaks for the magmatic population suggesting Neoarchean – Paleoproterozoic provenance. Metamorphic zircons from the khondalites yield ages of 1931 ± 33 Ma, 1871 ± 11 Ma and 1866 ± 10 Ma. The spot ages range from 1923 Ma to 1832 Ma suggesting either a long-lived metamorphic event or two distinct thermal events. The REE patterns of the zircon grains also clearly distinguish the magmatic and metamorphic populations. The garnet + sillimanite assemblage is considered to represent the peak UHT assemblage and the cordierite + biotite represents the post-peak retrograde assemblage. The ca. 1923–1832 Ma ages obtained in our study from metamorphic zircon domains correlate well with similar ages reported for metamorphism associated with the amalgamation of crustal blocks within the North China Craton. Our study suggests that the Late Paleoproterozoic UHT metamorphism in the central Korean Peninsula might be part of a common event within the Sino-Korean Craton related to the tectonics of final assembly of cratonic blocks within the Columbia supercontinent. Although a substantial volume of the Paleoproterozoic basement of the Korean Peninsula was destroyed and recycled during the Neoproterozoic and Phanerozoic tectonic events, the preserved remnants provide insights into the contiguity of the basements of the Korean Peninsula and the North China Craton.

The Calabria-Peloritani Orogen, a composite terrane in Central Mediterranean; its overall architecture and geodynamic significance for a pre-Alpine scenario around the Tethyan basin

The Calabria-Peloritani Orogen is an arcuate segment of the peri-Mediterranean orogenic Alpine nappe system that comprises the whole Calabria and the north-eastern sector of Sicily. It comprises the Sila and Catena Costiera Massifs in northern Calabria, the Serre and Aspromonte Massifs in central and southern Calabria, and the Peloritani Mountains in Sicily. In Sila and Catena Costiera Massifs, three tectonic complexes are recognisable: a) the basal Apennine Complex, which consists of carbonate platform sequences of passive continental margin; b) the intermediate Liguride Complex, made of oceanic-derived units, affected by HP/LT metamorphism; and c) the upper Calabride Complex, which represents a nearly entire section of continental crust. The Catanzaro Line separates the northern sector from the Serre Massif that also represents a nearly entire segment of Variscan continental crust unaffected by Alpine metamorphism. Further to the south, the Palmi Line separates the Serre from the Aspromonte Massif and the Peloritani Mountains. These two latter nappe edifices consist of either Variscan metamorphic units, Variscan units with Alpine overprint and units of continental derivation that are exclusively affected by Alpine metamorphism. The comparison between the geological evolutions of the various chain sectors, as well as their structural setting and their direction of tectonic transport, indicates that the Calabria-Peloritani Orogen is a composite terrane derived from the amalgamation of crustal blocks of different continental provenance. Northern Calabria represents a fragment of the Adria palaeomargin, whereas southern Calabria and northeastern Sicily are relics of an accretionary wedge resulting from the deformation of the European continental margin. As a consequence, nowadays a segment of the Europe-Adria collisional suture crops out in central Calabria.

Geochronological framework and tectonic setting of the granitic magmatism in the Chaihe–Moguqi region, central Great Xing’an Range, China

We compiled and analyzed 56 U–Pb zircon ages, including 38 ages obtained during the present study and 18 from other sources, for granitic rocks of the Chaihe–Moguqi region, central Great Xing’an Range, China. Magmatism in this area can be divided into eight stages: Early Devonian (399±3Ma), Late Devonian (365–358Ma), Late Carboniferous (322–299Ma), Early Permian (295–282Ma), Late Triassic (231–227Ma), Early–Middle Jurassic (179–172Ma), Late Jurassic (152–149Ma) and Early Cretaceous (137–120Ma). Granites were mainly emplaced during the latter four (Mesozoic) stages of magmatism. Paleozoic granites formed during several stages, and were associated with oceanic subduction and the amalgamation of crustal blocks in the eastern fragment of the Central Asian Orogenic Belt. The Late Triassic is an important period with respect to the change from the Paleo-Asian Ocean tectonic regime to the circum-Pacific tectonic regime. The formation of Late Triassic granites may have been related to post-orogenic lithospheric extension after closure of the Paleo-Asian Ocean. Early–Middle Jurassic granites resulted from either subduction of the Paleo-Pacific Plate or subduction during the amalgamation of the Jiamusi Massif and the Songliao terrane, whereas the intrusion of Late Jurassic–Early Cretaceous granites was associated with both the subduction of the Paleo-Pacific Plate and the closure of the Mongol–Okhotsk Ocean.

Palaeoproterozoic episodic magmatism and high‐grade metamorphism in the North China Craton: evidence from SHRIMP zircon dating of magmatic suites in the Daqingshan area

The Daqingshan area in the North China Craton (NCC) incorporates several suites of magmatic intrusives including gabbros, granodiorites, charnockites and syenogranites, which were overprinted by subsequent metamorphic events. In this study, we report detailed morphological and textural characteristics as well as sensitive high resolution ion microprobe (SHRIMP) U–Pb ages of zircons from ten representative samples of the magmatic suites including syenogranites, charnockites and granodiorites. The zircons in these rocks are characterized by typical magmatic crystallization features including elongate prismatic grains with angular to sub‐angular faces which are overprinted by a variety of reworked textures indicating strong recrystallization. These structures are terminated by thin and variable metamorphic overgrowths. U–Pb analyses of the zircons reveal multiple tectono‐thermal events including magmatic crystallization at 2.30–2.00, 1.96–1.94 and 1.85–1.82 Ga and metamorphic overprint at 1.97–1.94 and 1.87–1.82 Ga. The episodic magmatism and regional metamorphism recorded in our study show a complex sequence of tectonic processes during the early to late Palaeoproterozoic associated with the amalgamation of crustal blocks within the NCC, with the youngest episode of the syenogranites representing regional extension at the end of the final cratonization of the NCC. Copyright © 2012 John Wiley & Sons, Ltd.

Crustal structure and signatures of recent tectonism as influenced by ancient terranes in the western United States

The amalgamation of crustal blocks that composes the western cordillera of North America has a long history of deformation across a broad zone. Investigations spanning a range of scales in the region have sought to unravel details of its structure and evolution. By sampling the entire western portion of the United States, the deployment of the Transportable Array component of the EarthScope USArray provides broadband seismic data to study crustal structure across much of this deforming region. Receiver functions recorded across the western United States provide insight into the thickness of the crust and how it varies between tectonic provinces. The thickness of the crust varies from 50 km beneath the Rocky Mountains in Colorado and Wyoming. Distinct crustal structures characterize the Basin and Range, Snake River Plain, the Sierra Nevada, and the active Cascade volcanic arc, suggesting that the recent tectonic processes that affected the region have shaped the crustal structure. In addition, characteristics of the crust appear to relate to the boundaries of, and structures within, the terranes that formed North America. Patterns of crustal thickness across an expansive region presented here allow for the crustal response to specific tectonic processes to be determined while still imaging small-scale structures that can be more difficult to identify in a continental-scale study. This provides a context for previous and future detailed studies to understand how observed crustal structures relate to the evolution of western North America.

Tectonic Evolution and Paleogeography of Europe

The goal of this study was to use the tectonic framework of European craton to constrain our understanding of the sedimentary basins of Europe. An understanding of the amalgamation of the crustal blocks of Europe during the Caledonian, Hercynian, and Alpine orogenies was accomplished using an Evans and Sutherland system. Paleogeographic maps were ;made and integrated with the plate reconstruction with an eye toward how regional plate-scale events affect play elements in the basins. Europe is an artifact of Phanerozoic tectonic history, an amalgamation of crustal blocks without a precambrian nucleus of it own. This is in direct contrast of Africa, Asia, and North America. Multiple riftings and collisions created extremely complex mountain building during the Caledonian, Hercynian, Cimmerian, and Alpine orogenies. Basins are diverse, superimposed, and have long-lived tectonic histories with complex structuring and highly variable play elements. The Hercynian orogene set up the framework for northern European hydrocarbon systems. Its collapse set up the Apulian Mesozoic hydrocarbon system. Alpine deformation and tectonically related extension in turn set up the Neogene hydrocarbon systems of the Carpathians Pannonian basin and the Apennines. Eleven paleogeographic maps were completed at a scale of 1:5,000,000. There are four for the Paleozoic to showmore » the Hercynian orogeny and its subsequent foredeeps, and four for the Mesozoic, showing Tethyan rifting and associated subsidence, as well as the Cimmerian orogenies and start of Alpine deformation. The three time slices in the Cenozoic show the Alpine orogene and its foredeeps and the tectonically related extensional basins.« less