Zusammenfassung
Die Produktion von Granitschmelzen im grö\eren Ausma\e erfordert die Beteiligung kontinentaler Kruste. Die Kruste wird aufgeschmolzen, wenn sie von unten durch eine Wärmeanomalie des Mantels aufgeheizt wird oder wenn sie mächtiger als 40 km wird. Der Ort des Aufschmelzens und die Zeitabfolge des Schmelzens, die im Zusammenhang mit Subduktion Plattenstapelung und Kollisionsprozessen ablaufen, sind äu\erst komplex. Diese Prozesse sind mindestens auf sechs verschiedene Areale zu lokalisieren, in denen Aufschmelzung möglich ist. Die endgültige chemische und isotopenchemische Zusammensetzung von Granitschmelzen hängt von einer sehr komplexen Proze\abfolge ab, wobei zu berücksichtigen sind: Die Zusammensetzung des Ausgangsmaterials, die Zusammensetzung subduzierten Materials, Magmenmischung, Magmenunterströmung und Proze\e der Assimilation, Fraktionierung und Abkühlung. Um die Dynamik einer Granitschmelze zu erkennen, bedarf es moderner seismischer und geoelektrischer Methoden in Gegenden, wo die kontinentale Kruste ungewöhnlich dick oder hei\ ist.
Abstract
The production of melts of the granite clan on a significant scale requires participation of continental crust. Such crust will melt when heated from below by a mantle thermal anomaly, or when thickend to 40 km or more. Sites of melting, and the time sequences of melting associated with subduction and underplating processes, and collision processes, are complex. In both these processes, at least six melting sites may be involved. The final chemical and isotopic composition of granitic melts depends on a very complex array of processes, which include: source composition, composition of subducted materials, magma mixing, magma underplating, assimilation-fractionation-cooling processes. Resolution of granite melt dynamics requires an integrated attack, using modern seismic and electrical measurements, in regions where the continental crust is abnormally thick or hot.
Résumé
La production en quantité importante de liquides de la famille granitique requiert la participation de la croûte continentale. Celle-ci fond lorsqu'elle est chauffée d'en bas par une anomalie thermique du manteau, ou quand son épaisseur s'accroÎt jusqu'à 40 km ou plus. Les endroits où se développe la fusion, ainsi que son déroulement temporel, associé aux processus de subduction et d'underplating, sont complexes. Pour chacun de ces deux processus, six sites de fusion ou moins peuvent Être définis. Les compositions chimique et isotopique finales des liquides granitiques dépendent d'un ensemble de processus très complexes, qui comportent: la composition de la source, la composition des matériaux subductés, le mélange de magmas, les processus d'assimilation, de fractionement et de refroidissement.
La compréhension de la dynamique de la fusion granitique requiert une approche intégrée qui comporte la mise en oeuvre de méthodes sismiques et géoélectriques modernes dans des régions où la croûte continentale est anormalement chaude ou anormalement épaisse.
кРАткОЕ сОДЕРжАНИЕ
Дль ОБРАжОВАНИь гРАН ИтНых МАссИВОВ тРЕБУ Етсь УЧАстИЕ МАтЕРИкОВОИ кОРы. кОРА ЁтА РАсплАВ льЕтсь, ЕслИ ОНА пОДОгРЕВАЕт сь В РЕжУльтАтЕ АНОМА лИИ МАНтИИ, ИлИ, ЕслИ МОЩНОсть ЕЕ п РЕВышАЕт 40 кМ. кАк тОЧкА РАсплАВлЕНИь, т Ак И ВРЕМЕННАь пОслЕДОВАтЕльНОсть ЁтОгО пРОцЕссА стОьт В тЕсНОИ жАВИсИМОстИ От пРОцЕссОВ кОллИжИ И И жАсАВыВАНИь плИт. Ё тИ пРОцЕссы УстАНОВлЕН ы, пО кРАИНЕИ МЕРЕ, В шЕ стИ РАжлИЧНых АРЕАлАх, гД Е ВОжМОжНО РАсплАВлЕ НИЕ кОРы. хИМИЧЕскИИ И ИжО тОпНыИ сОстАВ ОБРАжО ВАВшИхсь гРАНИтОВ жАВИсИт От ц ЕлОгО РьДА слОжНых пРОцЕссОВ, пРИЧЕМ жДЕ сь слЕДУЕт пРИНИМАть ВО ВНИМАНИЕ: сОстАВ ИсхОДНОгО МАт ЕРИАлА, сОстАВ жАсАсы ВАЕМОгО МАтЕРИАлА, сМЕшАНИЕ М АгМ, пОДкОРОВыЕ пОтОк И МАгМ И пРОцЕссы АссИМ ИльцИИ, ФРАкцИОНИРОВ АНИь И ОхлАжДЕНИь. ЧтОБы Ус тАНОВИть ДИНАМИкУ гР АНИтНОгО РАсплАВлЕНИь, НЕОБхО ДИМО пРИМЕНьть сЕИсМИЧЕскИЕ И гЕОЁл ЕктРИЧЕскИЕ МЕтОДы В тЕх тОЧкАх, гДЕ МАтЕРИкОВАь кОРА ИМЕЕт НАИБОльшУУ МОЩ НОсть, ИлИ БОлЕЕ ВысОкУУ тЕМ пЕРАтУРУ.
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Fyfe, W.S. Granites and thermal structures in the lithosphere. Geol Rundsch 76, 15–22 (1987). https://doi.org/10.1007/BF01820570
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DOI: https://doi.org/10.1007/BF01820570