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| Titel |
Metamorphic Evolution of the Main Collisional Suture Zone Between East and West Gondwana |
| VerfasserIn |
Tamer Abu-Alam, Eugene Grosch |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250080721
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| Zusammenfassung |
| Petrological and metamorphic constraints from five metamorphic complexes which were
exhumed during the collision between East- and West-Gondwana across the main collisional
suture zone are presented. These include: (a) Meatiq complex in Eastern Desert of Egypt, (b)
Feiran-Solaf complex in Sinai, Egypt (c) Sa’al-Zaghra complex in Sinai, Egypt, (d) Great
Ruaha River area in the Mozambique Belt, and (e) Western Dronning Maud Land, East
Antarctica. The metamorphic results from these complexes are compared and provide
insight into the nature of Pan-African crust formation processes during Gondwana
assembly. In this study we present differences and similarities between various
field areas in the central collisional suture zone of Gondwana that sheds light on
the crustal accretion and supercontinent assembly process from a metamorphic
perspective. Â
The Meatiq complex in the Eastern Desert of Egypt consists of a low-grade volcanic arc
sequence that covers a higher-grade, biotite-garnet gneiss metamorphic core complex. A
sinistral shear zone - the Najd Fault System - separates the high-grade rocks from the
low-grade volcanic sequence. The combination between published data and new
thermodynamic modeling shows that both the high-grade and the low-grade rocks record
single clockwise P -T paths. The peak metamorphic conditions of the high-grade rocks are
T = 650-700 oC and P = 7-7.5 kbar, whereas the low-grade rocks record conditions of T =
400-450 oC and P = 3-4 kbar.
In Sinai, the Najd Fault System is not exposed due to the voluminous intrusion of ca. 540
Ma post-tectonic granites. However, both the garnet-biotite gneisses of the Feiran-Solaf
complex (T = 700-750 oC and P = 7-8 kbar) and the low-grade rocks (T = 400-450 oC and P
= 2-3 kbar) of Wadi El Kid record very similar metamorphic conditions and clockwise P -T
paths to those in Eastern Desert, Egypt. Conversely, the Sa’al-Zaghra complex shows
anticlockwise P-T path with peak conditions of 2.5 kbar and 42 oC. It worth mention that the
peak metamorphic age of the Sa’al-Zaghra complex is much older than the Pan-African event
(ca. 1100 Ma).
In western Dronning Maud Land (Antarctica), a petrological and metamorphic
comparison of Mesoproterozoic metabasic rocks on the eastern margin of the Archean
Grunehogna Craton and the adjacent Maud Belt, revealed a difference in peak metamorphic
conditions from T = 280 ± 30 oC to 710-750 oC and P = 2 ± 1.5 to 8.5-11 kbar over a
distance of only 30 km across a major glacial valley. The high-grade PT-constraints derived
for the western extreme of the Maud Belt, is very similar to that reported for the eastern Maud
Belt dated at ca. 550 Ma. These PT-constraints do not support the presence of a westward
decreasing metamorphic field gradient within the Maud Belt as previously proposed. The data
presented here suggests that the inferred sub-glacial boundary between the Grunehogna
Craton and the Maud Belt, might reflect a major Pan-African thrust, with the Maud Belt
representing the continuation of the East African Mozambique Belt into East Antarctica. |
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