الفهرس | Only 14 pages are availabe for public view |
Abstract from the preceding discussions.it is dear that both GebelE1hadidand UmmNar areas have undergone a quite similar history of deformation. CORCLUSIORS : L The area is covered mainly by two allochthonous terrlans, juxtaposed alOl18 a major E-W thrust. The southern terrain represents the hanging wall of the thrust and is comPOsedof metagreywaekes and metamudstones associated with Algoma-type banded iron-formation. The footwall to the north is occupied by ultramafic- mafic (metaserpentinitesi metapyroxenites and metagabbros) and metabasaltic fragments incorporated in a matra of sheared serpentinites and slates. 2. Analysis of a composite sample representing three chip samples collected along the exposed pyrite-bearing iron-formation horizon in the southern terrian gave 0.53 ppm gold and 2.15 ppm silver. The gold value indicates an enrichment about three times the average world value of the Algoma-type banded iron-formation. More analyses are needed to determine the exact.gold content. 3. The ophiolitic melaDaerocks are considered to represent an ocean- or back-arc lithosphere. while the iron bands-bearing metasediments are considered to be of island-arc affinity. 4. The structural contact between the two terrians is inferred by the presence of a narrow zone of mylonite separating the two terrains. and also by the remarkable differences in nature. extension and distribution of the rocks on both sides of the myloniticzone. 94 ~. The iron bands-bearing metasediments were folded forming a major anticline. plunging moderately SE. 6. Tbe area has undergone a structural history involving three deformational pbases Df• D2 and D3, L The first phase of deformation D. is manifested by few isoclinal and recumbent fold closures refolded by and included within the limbs of D2 folds. such refolded folds are not recorded in the melange rocks, b. The serond phase or deformation D2 is a major event in intensity and extent and resulted in the Corm.ationor tight overturned and isoclinal folds. plunging moderately SE. The maior overturned anticline occupyingthe southern terrain is couial with D2 folds, c. D 3 deformation is of much less intensity than D2, It is not a widespread feature throughout the area, represented by open folds plunging SW, D3 folds are nicely sbown in the micaceous scl1ists present in the ertreme southern part of the area |