Crustal Growth by Magmatic Accretion Constrained by Metamorphic P-T Paths and Thermal Models of the Kohistan Arc, NW Himalayas |
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Authors: | YOSHINO TAKASHI; OKUDAIRA TAKAMOTO |
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Institution: | 1 INSTITUTE FOR STUDY OF THE EARTH'S INTERIOR, OKAYAMA UNIVERSITY, YAMADA 827, MISASA, TOTTORI 682-0193, JAPAN
2 DEPARTMENT OF GEOSCIENCES, GRADUATE SCHOOL OF SCIENCE, OSAKA CITY UNIVERSITY, 3-3-138 SUGIMOTO, OSAKA 558-8585, JAPAN |
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Abstract: | Magmatic accretion is potentially an important mechanism inthe growth of the continental crust and the formation of granulites.In this study, the thermal evolution of a magmatic arc in responseto magmatic accretion is modeled using numerical solutions ofthe one-dimensional heat conduction equation. The initial andboundary conditions used in the model are constrained by geologicalobservations made in the Kohistan area, NW Himalayas. Takingconsideration of the preferred intrusion locations for basalticmagmas, we consider two plausible modes of magmatic accretion:the first involves the repeated intrusion of basalt at mid-crustaldepths (intraplate model), and the second evaluatesthe simultaneous intrusion of basalt and picrite at mid-crustaldepths and the base of the crust respectively (double-platemodel). The results of the double-plate model accountfor both the inferred metamorphic PT paths of the Kohistanmafic granulites and the continental geotherm determined frompeak PT conditions observed for granulite terranes. Thedouble-plate model may be applicable as a key growth processfor the production of thick mafic lower crust in magmatic arcs. KEY WORDS: thermal model; magmatic underplating; PT path; granulite; lower crust |
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Keywords: | : thermal model magmatic underplating P T path granulite lower crust |
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