الفهرس 
CHAPTER 1 INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 307 |  |  |
| | | from | 307 | | |
Abstract
The present study deals with geology, petrography, geochemistry and age dating of banded iron formation (BIF) and their host rocks in three localities of BIFs in the Eastern Desert of Egypt namely
from south to north Um Nar, El Dabbah and Um Anab. Um Nar area is located at NW Marsa Alam
city, Central Eastern Desert of Egypt and is located between latitudes 25° 14′ 4″ and 25° 16′ 25″ N and
longitudes 34° 14′ 58″ and 34° 19′ 58″ E. Wadi El Dabbah area is located in the central part of Eastern
Desert (SW of Quseir city) between latitudes 25° 45′ 50″ and 25° 50′ 50″ N and longitudes 34° 7′ 42″
and 34° 10′ 48″ E. Um Anab area, northern Eastern Desert of Egypt and is located between latitudes
26° 50′ and 26° 54′ N and longitudes 33° 29′ and 33° 32′ E.
The exposed rocks in Um Nar area (72 km2) are serpentinites and related rocks, metagabbro,
quartz plagioclase mica schist (including pebbly schist), amphibole schist (including hornblende schist,
tremolite-actinolite schist and epidote schist), metacarbonate, banded iron formation, mica schist
hosting BIFs and dykes and veins.
The exposed rocks of El Dabbah area (43 km2) represent nearly complete succession of
oceanic crust from the older to the younger: serpentinites and related rocks, metagabbros , lava flow
including lavas with feldspar megacrysts “megacrysts porphyrites”, metacarbonate, pillow lava,
banded iron formations (BIFs), tuffs, sedimentary sandstone, diamictites (poorly sorted conglomerate.
These rocks are metamorphosed up to the green schist facies represented by tremolite-actinolite,
chlorite and epidote and show inherited primary structures and textures (lava flow, pillow lava, shards
of volcanic glass and lamination in tuffs).
The exposed rock units in Um Anab area (44 km2) are represented by the metavolcanics,
amphibole schist and metatuffs which occupy the central part of the area and host the BIFs and the
metacarbonate. The younger granites occur in the northern part while the older granites are in the
southern part.
Pan-African amphibole schist, amphibolite and mica schist hosting Banded Iron Formations
(BIFs) outcrop at Um Nar and Um Anab areas represent a part from the old ocean bottom. The two
areas are about 200 km2 apart, the mutual features are the original tectonic setting, grade of
metamorphism, the similar lithology and hosting BIFs and sedimentary carbonate beds, however the
northern part of um Anab is still fresh as evidenced by the well preserved pillow lava. These rocks are
metamorphosed up to the amphibolite facies with the development of garnet as an index mineral in Um
Nar area. In the field these rocks show strong foliation where the metamorphism almost obliterated all
the original primary structures, nevertheless some relict features can be interpreted as pillow lava in
Um Nar area. Of course the situation of the iron beds can delineate the original bedding, which is
parallel to the foliation, however in Um Nar area where we have overturned asymmetrical anticline (?)
it is doubt to accept always this common interpretation because the beds are very steep and it is not
certain to define the upper surface of the beds.
Geochemically, it is believed that the rocks suites in both Um Nar and Um Anab are mainly
tholeiitic to slightly calc-alkaline were developed during the early stages of the arc setting during the
pan-African orogeny. The association of the oceanic crust rock staff with BIFs and carbonate which
overlain by diamictite and poorly sorted massive sandstone in El Dabbah area could refers to prevailed
snowball earth at that time which allowed alternating periods of oxic/anoxic. El Dabbah area represents
almost ideal succession of ophiolite. It can be concluded also that the thickness of the oceanic crust is
about 7 km