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The Yanshan orogeny and late Mesozoic multi-plate convergence in East Asia—Commemorating 90th years of the “Yanshan Orogeny”
The Yanshan movement/orogeny has been proposed for 90 years, which is of special significance in the history of geological research in China. This study conducted a review by synthesizing major achievements regarding episodic deformation features, sedimentary and magmatic records of the Yanshan orogeny in China, and clarified the episodic tectono-magmatism and its geodynamic origins. The tectonic implications of the Yanshan orogeny are discussed in the context of global plate tectonics and supercontinent reconstruction. Lines of evidence from structural, sedimentary and magmatic data suggest that the Yanshan orogeny represents a regional-scale tectonic event that affected the entire China continent in late Mesozoic period. Numerous age and structural constraints consistently indicate that the Yanshan orogeny was initiated in the Jurassic (at ∼170±5 Ma). and was characterized by alternating stages of crustal shortening at ∼170–136 Ma, crustal extension at ∼135–90 Ma, and weak shortening at ∼80 Ma. The 170–136 Ma crustal shortening was reflected in the generation of two regional stratigraphic unconformities (the Tiaojishan and Zhangjiakou unconformities), which were initially named the A and B episodes of “the Yanshan Orogeny” by Mr. Wong Wenhao in 1928. Geodynamically, the Yanshan orogeny in East Asia was associated with nearly coeval oceanic subduction and continental convergence in the Paleo-Pacific, Neo-Tethys, and Mongol-Okhotsk tectonic domains. As a consequence, three giant accretionary-collisional tectonic systems were formed along the continental margins of East Asia, i.e., the Mongol-Okhotsk, Bangonghu-Nujiang, and SE China subduction- and collision-related accretionary systems. The Yanshan orogeny induced widespread crustal-scale folding and thrusting, tectonic reactivation of long-lived zones of crustal weakness, and extensive magmatism and mineralization in intraplate regions. Based on the time principle of supercontinent assembly and break-up, we propose that the mid-Late Jurassic multi-plate convergence in East Asia might represent the initiation of the assembly of the Amasia supercontinent, and the Yanshan orogeny might be the first “stirrings” that is a prerequisite for the birth of the Amasia supercontinent.
Journal Article
Plate tectonics : continental drift and mountain building
This volume presents an introduction to the field of plate tectonics. Plate tectonics is a scientific theory which describes the large scale motions of Earth's rigid outermost shell. The authors begin with an historical introduction concerning early ideas of continental drift and Earth dynamics that leads into discussion and consideration of plate motions and geometry. This is followed by several chapters that define, describe in detail, and illustrate the various features, processes, and settings that comprise the plate tectonic realm: graben structures, passive continental margins, ocean basins, mid-ocean ridges, subduction zones, and transform faults. The remaining chapters deal with mountain-building processes as a consequence of plate tectonics and the collision of terranes and large continents. These chapters illuminate plate tectonic processes from the early history of the Earth to the present.-- Source other than Library of Congress.
Book
The Atlas of Morocco: A Plume‐Assisted Orogeny
We explore the connections between crustal shortening, volcanism, and mantle dynamics in the Atlas of Morocco. In response to compressional forces and strain localization, this intraplate orogen has evolved far from convergent plate margins. Convective effects, such as lithospheric weakening and plume‐related volcanism, contributed in important ways to the building of high topography. We seek to better understand how crustal and mantle processes interacted during the Atlas' orogeny by combining multiple strands of observations, including new and published data. Constraints on crustal and thermal evolution are combined with new analyses of topographic evolution, petrological, and geochemical data from the Anti‐Atlas volcanic fields, and a simple numerical model of the interactions among crustal deformation, a mantle plume, and volcanism. Our findings substantiate that: (a) crustal deformation and exhumation accelerated during the middle/late Miocene, contemporaneous with the onset of volcanism; (b) volcanism has an anorogenic signature with a deep source; (c) a dynamic mantle upwelling supports the high topography. We propose that a mantle plume and the related volcanism weakened the lithosphere beneath the Atlas and that this favored the localization of crustal shortening along pre‐existing structures during plate convergence. This convective‐tectonic sequence may represent a general mechanism for the modification of continental plates throughout the thermo‐chemical evolution of the supercontinental cycle. Key Points Crustal thickening is limited and cannot account for the topography elevation of the Atlas system Resumption of volcanism is contemporaneous with the acceleration of crustal deformation and topography growing The erosion and weakening of the lower lithosphere, as a consequence of mantle plume, may enhance crustal deformation and exhumation
Journal Article
Orogenesis : the making of mountains
\"Orogenesis, the process of mountain building, occurs when two tectonic plates collide--either forcing material upwards to form mountain belts such as the Alps or Himalayas or causing one plate to be subducted below the other, resulting in volcanic mountain chains such as the Andes. Integrating the approaches of structural geology and metamorphism, this book provides an up-to-date overview of orogenic research, and an introduction to the physico-chemical properties of mountain belts. Global examples are explored, the interactioning roles of temperature and deformation in the orogenic process are reviewed, and important new concepts such as channel flow are explained. This book provides a valuable introduction to this fast-moving field for advanced undergraduate and graduate students of structural geology, plate tectonics and geodynamics, and will also provide a vital overview of research for academics and researchers working in related fields including petrology, geochemistry and sedimentology.\"-- Provided by publisher.
Book
The birth of the Alps: Ediacaran to Paleozoic accretionary processes and crustal growth along the northern Gondwana margin
New whole-rock geochemical and coupled U–Pb and Lu–Hf LA-ICP-MS zircon data of metasedimentary rocks of the Austroalpine, South Alpine and Penninic basement domains are presented, to disentangle the pre-Variscan tectonic evolution of the proto-Alps. The studied units seem to record distinct stages of protracted Late Ediacaran to Carboniferous tectonosedimentary processes prior to the Variscan collision. In the case of Austroalpine and South Alpine units, nevertheless, no major differences in terms of provenance are observed, since most detrital zircon samples are characterized by a major Pan-African peak. Their detrital zircon spectra record a provenance from the northeastern Saharan Metacraton and the Sinai basement at the northern Arabian-Nubian Shield, being thus located along the eastern Early Paleozoic northern Gondwana margin, whereas sources located further west are inferred for the Penninic Unit, which might have been placed close to the Moldanubian Unit of the Bohemian Massif. In any case, it is thus clear that the Alpine basement remained in a close position to the Gondwana mainland at least during the Early Paleozoic. The Late Ediacaran to Silurian tectonic evolution, which includes Cadomian and Cenerian tectonometamorphic and magmatic processes, seem thus to record a continuum related to a retreating-mode accretionary orogen, with diachronous back-arc basin opening and possibly discrete compressional/transpressional pulses linked to changes in subduction zone dynamics. On the other hand, it is inferred that the Alpine basement essentially comprises Pan-African metasedimentary and subordinate metaigneous rocks, possibly with very few Early Neoproterozoic relics. This basement was significantly reworked during the protracted Paleozoic orogenic evolution, due to anatexis and/or assimilation by mantle-derived juvenile magmatism.
Journal Article
Tectonic evolution of the Caledonian orogeny in Scotland: a review based on the timing of magmatism, metamorphism and deformation
Classic tectonic models for the Caledonian orogeny in Scotland involve Ordovician collision of Laurentia–Midland Valley arc (Grampian orogeny), followed by middle Silurian collision of Laurentia–Baltica (Scandian orogeny) and 500–700 km of sinistral displacement along the Great Glen fault separating the Northern Highlands (Moine Supergroup) from the Grampian Highlands (Dalradian Supergroup). A review of the timing of magmatic and metamorphic rocks across Scotland allows a simpler explanation that fits with a classic Himalayan-style continent–island arc–continent collision. Late Cambrian – Early Ordovician NW-directed ophiolite obduction (Highland Border complex) coincided with the ending of stable continental shelf sedimentation along the eastern margin of Laurentia. Following collision between Laurentia and the Midland Valley arc–microcontinent in Early Ordovician time, crustal thickening and shortening led to almost continuous regional metamorphism from c. 470 to 420 Ma, rather than two discrete ‘orogenies’ (Grampian, Scandian). U–Pb monazite and garnet growth ages indicating prograde metamorphism, and S-type granites related to melting of crustal protoliths are coeval in the Grampian and Northern Highlands terranes. There is no evidence that the Great Glen fault was a terrane boundary, and strike-slip shearing post-dated emplacement of Silurian – Early Devonian granites. Late orogenic alkaline granites (c. 430–405 Ma) in both Moine and Dalradian terranes are not associated with subduction. They are instead closely related to regional alkaline appinite–lamprophyric magmatism resulting from simultaneous melting of lower crust and enriched lithospheric mantle. Caledonian deformation and metamorphism in northern Scotland, with continuous SE-directed subduction, show geometry and time scales that are comparable to the Cenozoic India–Kohistan arc–Asia collisional Himalayan orogeny.
Journal Article
Toward a stepwise Kwangsian Orogeny
The Kwangsian Orogeny originated along the southeast coast of China and stepwise developed in a northwest direction.It includes two stages,a long locally varying uplift from the Late Ordovician to the early Silurian and a finally tectonic movement near the Silurian and Devonian transition.The Kwangsian uplift event shows a stepwise delay northwestwards from the southeastern coast area in Nemagraptus gracilis Biozone（Sa1）to the south side of the Xuefeng Mountains in or later than Cystograptus vesiculosus Biozone（R3）to Coronograptus cyphus Biozone（R4）.In the southern of Yangtze Platform,the Yichang Uplift was droved by the Kwangsian Orogeny forming a diachronous stratigraphical break through Rhuddanian and Aeronian.The distribution of the early Telychian lower marine red beds indicates a northwestward increase of the Cathaysian Oldland.Stratigraphical evidence may explain why the Kwangsian movement was marked by an angular disconformity during the Pridoli to earliest Devonian interval.
Journal Article
Tectonics of South China Continent and its implications
This paper aims at exploring the tectonic characteristics of the South China Continent （SCC） and extracting the universal tec- tonic rules from these characteristics,to help enrich the plate tectonic theory and better understand the continental dynamic system. For this purpose, here we conduct a multi-disciplinary investigation and combine it with the previous studies to reas- sess the tectonics and evolution of SCC and propose that the tectonic framework of the continent comprises two blocks, three types of tectonic units, four deformation systems, and four evolutionary stages with distinctive mechanism and tectonic characteris- tics since the Neoproterozoic. The four evolutionary stages are： （1） The amalgamation and break-up of the Neoproterozoic plates, typically the intracontinental rifting. （2） The early Paleozoic and Mesozoic intracontinental orogeny confined by plate tectonics, forming two composite tectonic domains. （3） The parallel operation of the Yangtze cratonization and intracontinental orogeny, and multi-phase reactivation of the Yangtze craton. （4） The association and differentiation evolution of plate tectonics and intraconti- nental tectonics, and the dynamic characteristics under the Meso-Cenozoic modem global plate tectonic regime.
Journal Article
A felsic meta-igneous source for Li-F-rich peraluminous granites: insights from the Variscan Velay dome (French Massif Central) and implications for rare-metal magmatism
The Velay anatectic dome in the Variscan French Massif Central exposes a low-pressure–high-temperature metamorphic sequence, which represents an ideal natural laboratory for documenting the behavior of rare-metals and fluxing elements during crustal melting. We investigated the silicate and bulk-rock geochemistry of sub- to suprasolidus metapelites and orthogneisses, as well as related granites, and performed forward thermodynamically constrained geochemical modeling to quantify the respective effects of melting pressure, temperature, H
2
O activity, and protolith composition on the Li and F contents of granitic melts. We find that biotite compositions are good proxies of melt compositional evolutions during prograde melting. The crystallization of peritectic cordierite at low pressure (< 5 kbar) and “water-fluxed” melting both inhibit the Li enrichment of anatectic melts. Metapelite-derived melts consistently show modest Li–F contents, and a decoupling is observed as melts with the highest Li concentrations (~ 200–400 ppm) are produced below 750 °C, whereas F-richest melts (~ 0.2–0.4 wt%) are produced above 750 °C near the biotite-out isograd. Peraluminous orthogneiss anatexis can generate a melt that is concomitantly enriched in both F (~ 0.3–1 wt%) and Li (~ 600–1350 ppm) at relatively low temperature (< 750 °C), which can evolve toward rare-metal granite compositions (~ 10,000 ppm Li; ~ 2 wt% F) after 80–90 wt% of fractional crystallization. Melting of felsic meta-igneous rocks followed by magmatic differentiation is thus a viable mechanism to form Li-F-rich rare-metal granites and pegmatites, providing a direct link between protracted crust recycling and rare-metal magmatism in late-orogenic settings.
Journal Article