フィッション・トラック

ニュースレター 第23号

8-9

2010年

Evolution and Thermo-Tectonic Development of The Basementcomplex, West-central Sinai, Egypt: Constraints from Uranium-Lead
Dating and Apatite Fission Track Low-Temperature Thermochronology
Sherif Mansour* and Noriko Hasebe***Graduate School of Natural Science and Technology, Kanazawa University** Institute of Nature and Environmental Technology, Kanazawa University
Abstract

Oligocene-Miocene as response to four

This study focuses on relatively small area

tectonic events caused by subduction-relatedin Sinai to reconstruct detailed thermal anderosion which was ﬁnished by the Cambrian

tectonic histories of representative rock units

time, collision between Gondwana andfor Sinai. Sixteen samples were collected all

Laurasia (Hercynian tectonic event), breakover the area of study. Zircon U-Pb dating

apart of Gondwana and/or opening of Mid-technique was applied on thirteen samples.

Atlantic and the Gulf of Suez formation,

Three intense magmatic activities control therespectively. Interestingly these tectonic

scheme of the basement classiﬁcation; Early-

events aﬀected three regions which areorogenic metamorphic magmatic activity

separated spatially represent diﬀerential

occurred in a time span extended from 861 tomovement most probably along fault-bounded

807 Ma, Syn-orogenic grey and red granites

blocks or anticline syncline relationship (Fig.

occurred in a time span extended from 748 to2). The Gulf of Suez is a passive type rift

739 Ma, and Late-orogenic magmatic activity

which formation was accompanied by low toin time span extended from 613 to 535 Ma.

moderate thermal overprinting on the rift

Each of Syn-orogenic and Late-orogenic

ﬂanks. These ﬂanks were uplifted from depths

activities were represented as series ofof 1-1.5 km with cooling rates of 8-12 ºC/Ma

granitic intrusions in which red granites form

and uplifting rates of 0.2-0.3 km/Ma.

instead of grey granites along with increasing
potash and changing into extensional
environment conditions. Pre-Pan-African
older zircon grains (2273, 1755, 1241, 1003

Referenceand 989 Ma) are possibly inherited from theisland-arc nucleus. Magmatic intrusions event

El-Bialy, M.Z., 2004. Petrologic, geochemicalin the Ordovician-Devonian time must beand pertogenetic characterization of theintense based on number of zircon grains ofold granites of Sinai, Egypt. Unpublishedthis age (Fig.1).

Ph.D. Thesis, Suez Canal University,Ismailia, Egypt, 230p.

Apatite ﬁssion track method was applied on
fourteen samples with operating 156 analyses
on 125 apatite grains to measure U, Th andPb isotopic concentrations and ratios inaddition to counting surface tracks, measuring
the HCTLs and Dpar in every analyzed grain.
Thermal histories were reconstructed for all
treated samples indicate four exhumation
events occurred in Precambrian, DevonianCarboniferous, Jurassic-Cretaceous and8Fig. 1. Age density histogram for zircons 238U/206Pb ages for all concordant grains;a) Pre-Pan-African agegrains, b) Pan-African age grains where b1 Early orogenic suite, b2 Syn orogenic suite and b3 Late orogenicsuite, c) Post-Pan-African age grains.

Fig. 2. Simpliﬁed Geologic Map for Gebel Samra area (modiﬁed after El-Bialy, 2004) representing the locationsof the studied samples and the three apatite FT age groups zones; A the Precambrian-Ordovician group, B theDevonian-Carboniferous group, C the Jurassic-Cretaceous group, see the text and table 4 for more details.

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