Mineral deposits in eastern south Sinai -Egypt
Um Zerriq Area
hassan BekheiteGeological Survey Of [email protected]
The present study aims at studying geology, petrography and geochemistry of some mineralized occurrences in southeastern Sinai along the gulf of aqaba, Wadi El kid. The studied area lies between latitude 28ْ 10َ 00ً&28ْ 30َ 00ً N and longitudes 34ْ 15َ 30ً & 34ْ 24َ 40ً E . These mineralized occurrences are located in include two areas . Umm Zerriq-kid area is located in the northwestern part ,while the El Samra area is located in the southeastern part .the asphaltic road between Sharm El shekh and Dahab cities connect Between the two areas with Distance about 25 km.several detailed geological maps and sketches were prepared at different scales (1:10,000,1:40,000 and 1:2000) for the different locations sites I, II, And III in Umm Zerriq-kid area .
Sampling in the investigated area had been carried out through a network of profiles ,trenches ,and stream sediments where the bed -rock ,Channels and alluvial sample had been collected respectively to represent all rock varieties .
More than 232 samples representing the different dock varieties were collected along different geological profiles and digged trenches ,as well as the drilled borehole.The collection of samples had been carried out using global position system (GPS) as a New technique in survey
More than 121 thin sections and polished surfaces had been prepared for studying the petrography of the rocks and ore minerals. The most of samples had been analyzed in the central laboratories of the geological survey of Egypt. Moreover 43 bed rock samples were analyzed for ore metals in southern Africa .
Several techniques of analysis had been used including Atomic Absorption, XRD, XRF, ICP and spectrograph techniques . The major elements of the bed rocks , in addition to its trace elements were analyzed by using XRF technique, while the identification Of the minerals in the mineralized rock units were detected by using XRD technique .The trace elements Au, Ag, Cu, Pb, Mo and Zn were analyzed by using Atomic Absorption spectroscopic method .The inductive coupled plasma (ICP) technique as used to analyze 43 Rock samples, collected from Umm Zerriq-kid area, for Au, Ag, Cu, Pb, Zn, Sb, C, Ni, Co, Fe, S and Mn.
More than 73 core samples had been collected covering the most vertical intervals of the digged borehole deren to 100m in depth.
Umm Zerriq --kid area is covered mainly with rocks of meta volcano -sedimentary successions of the kid group .The oldest rock unit in this area is the metasediments (chlorite, biotite, garnet and andalusite schists) interanted with the metatuffs (crystal and lithic metatuffs). These rocks possibly have been formed in low to medium grade regional metamorphism of green schist and the beginning of amphibolite grade. The metasediments are intruded by some masses of Feirani volcanics (Abu El Leil, 1992 ) characterized by their porphyritic texture. Sometimes, some masses of silicified carbonate meta --tuffs are mainly observed in the western side of the area. Several basic to acidic dykes differing in thickness and composition cut the area. Umm Zerriq-kid area is highly affected by large sets of structural elements reflecting different tectonic movements which had been happened through the different geological periods. According to the field observations and measurements, at least three phases of deformation are easily recognizable which reflect many types of lineation, folding, faulting, thrusting, gneissosity, cleavages and shear zones.the area is intensely folded and revealed many major and minor folds. The eastern part of the mapped area at sites II and III at Wadi kid are highly folded than the western part at site I Wadi Umm Zerriq. Many recumbent, tight, disharmonic, conjugate, open and ptygmatic folds are recorded with axial planes parallel to the general orientation of the foliation, but sometimes perpendicular to it. The general major folds trend NW-SE. The shear zones are observed in the schists and the metatuffs particularly associated with thrusting which are observed along both Wadi Umm Zerriq and Wadi kid at the three sites and Highly revealed in the eastern side of the area at site II. These mineralizations are exposed at the surface and occupy about 7 km2 , As well as their subsurface extension reaches up to 100 m (at site II ) as the collected core samples from the drilled bore- hole indicated. Structurally the mineralizations are highly controlled where the highly mineralized zones occur in highly deformed zones . Also the mineralization potentially increases with increase of the grade of metamorphism.
El Samra area is built up mainly of metavolcano- sedimentary succession (chlorite biotite schist and crystal lithic tuffs), Feirani volcanics (rhyodacites) and dyke system. Molybdenum-copper bearing stockwork is observed cutting across the crystal lithic tuffs. Gold bearing gossan and rhyolitic dykes are hosted in both chlorite biotite schist and rhyodacite porphyry of Feirani volcanics.many altered sheared belts are found stained by copper mineralization. The chlorite biotite schists are recorded in the mapped area in two locality, at the stockwork and sulphide location. They occur as greenish gray color, fine to medium-grained, strongly foliated elongated belts.The schistosity is striking NE-SW, with angle of dip varying from 300-400 toward east. The crystal lithic tuffs form low hills, occupying the foot of the chlorite biotite schist and considered the host rock of the Mo-Cu-bearing stockwork and Cu.bearing sheared rock. The rocks show bedding planes with dip 400 -600 to SSE and striking Generally NE. Feirani volcanics appear in variable colors (gray, grayish green, black and pinkish gray), highly jointed sometimes weathered, altered, brecciated and xenolithic.Several basic and acidic dykes are observed cutting all rock units of the investigated area with various trends. The main one striking NE-SW with thickness up to 3m. And extends more than 400m
Geochemical characters of the bed rocks hosting the mineralized rock units at Umm Zerriq-kid area are obtained through several variation diagrams, Harker variation diagrams, show that most of the values of TiO2 , Al2O3, Fe2O3, FeO and Mgo decrease with increase of SiO2 Value , while NaO2 increases, CaO, MnO and P2O5 Have constant tendency. Most the plots of the rocks fall in calc-alkaline field and few plots AFM diagram fall in tholeiitic field.the binary diagram of SiO2 vs k2O shows that the plots of most samples fall in the high k field . The ternary diagram of FeO*+TiO2-Al2O3- shows that most of the plots of the metavolcano-sedimentary rocks have calc-alkaline affinity. FeO*/MgO vs SiO2 diagram indicates that most of the investigated rocks have mixed affinities to tholeiitic and calc alkaline series. The plots in The total alkalis --SiO2 diagram shows that the most investigated rocks fall within subalkalic field. However, the plots of doleritic dykes and one sample of Feirani volcanics fall within the alkaline field. FeO-MgO-CaO, diagram indicates that the investigated rocks are relatively enriched in iron relative to calcium and magnesium oxides. K2O-Na2O-CaO diagram shows that the plotted samples of the investigated rocks are relatively enriched in k2O, as well as they are relatively poor in calcium and sodium.the MgO-CaO-Al2O3 Diagram demonstrates that investigated rocks are relatively rich in alumna and relatively poor in lime and extremely poor in magnesia.
For El Samra area AFM diagram shows that the plots of rhyodacite fall nearly in calc alkaline field, while the plots of doleritic dyke fall in tholeiitic field. Total alkalis' vs SiO2 diagram shows that, the plots of the investigated rocks fall within the subalkaline field while the doleritic dykes fall within the alkaline field. SiO2 and k2O diagram exhibits that, the most of the plots fall within the field of dacite and rhyolite of low k2O.the ternary diagram of FeO*+TiO2-Al2O3-MgO show that the most of the rocks fall in both calc-alkaline and tholeiitic field.
The recorded mineralization at Umm Zerriq-kid area (the three sites I, II, III) is mainly alteration zones, gossans, quartz veins, silicified carbonate metatuffs and rhyodacitic lenses bearing pyrite. Most of these modes of occurrence of mineralization are hosted in the metavolcano-sedimentary rocks (schists and tuffs ). The alteration zones recorded represent the main mineralization in the investigated area. They represent exposed parts of a shear zone extending mainly NW-SE within the metavolcano-sedimentary rock units. The alteration zones appear as elongated bodies, extending parallel to the schistosity and trending mainly NW-SE dipping to north and NNE-SSW dipping to east with angle of dip ranging from 30 0 -50 0 . These alteration zones extend up to 500 m with 2-20 m in thickness. They occur at three sites along wades Umm Zerriq and Kid. The gossans are found mainly associated with the alteration zones, hosted in the metavolcano-sedimentary rock units .They are as multicolored rounded and elongated pockets, distributed along the alteration zones, ranging in diameter from 30x40 cm to 2x3 m. Several types of quartz veins are recorded in the investigated area , hosted mainly in metavolcano- sedimentary Rocks .These types include, milky, smoky and iron --oxides bearing quartz veins. Most of them are deformed and concordant with the schistosity . The main bulk of these quartz veins is recorded in the eastern side of Wades Umm Zerriq-kid relative To the western side. Little of parallel sheeted veins rich in iron oxides are found along Wadi Umm Zerriq cutting across the metatuffs. They vary in thickness from few centimeters to 40 cm and extend more than 40 m. Both types, the deformed smoky quartz Lenses rich in white mica and the ferruginated quartz lenses bearing green flaky biotite are the most promising for gold mineralization
The silicified carbonate metatuffs are restricted mainly at the north west part of the investigated area along Wadi Umm Zerriq. They occur as highly jointed and cracked blocks, sandwiched within two types of alteration zones, one at the footwall, rich in iron oxides (mineralized ) and the another at the hang-wall, rich in chlorite and epidote (unmineralized).The silicified carbonate metatuffs host mainly copper mineralization (chalcopyrite, bornite, covellite and malachite), filling the carbonate bearing cavities within the rocks. The Clark of concentration values of the trace element shows that the highest C.C values are recorded in alteration zones, gossans and quartz veins, while the host rocks ( schists and tuffs ) show less C.C values. They also reveal the following:
Site I: Lead element is the main element in the profile samples and the associated elements are Zn, Cu and Sb.In the trench samples Ag is the main mineralizalion associated with Au, Pb, As, Cu and Ni
Site II: In the profile samples Ag is the main mineralizalion element while Au, Pb, Sb, Zn and Cu are the associated elements. In the trench samples Pb is the main mineralizalion element and the associated elements are Ag, Au, Zn and Cu
Site III: In the profile samples Ag is the main mineralization and As, Pb , Sb and Cu are the associated elements.In the trench samples Pb is the main mineralIztion elements and Au, Ag, Cu, As and Zn are the associated elements . However Cu shows abnormal C.C values in the tuffs at site I and in the schist at sites II & III, Arsenic shows extraordinary anomalous C.C values in both tuffs and schist.
These results can be summarized in the following geochemical spectra
Site I profile: Pb, Zn, Cu, Sb
Trench: Ag, Au, As, Cu, Ni
Site II profile: Ag, Au, Pb, Sb, Zn, Cu
Trench: Pb, Ag, Au, Zn, cu
Site III profile: Ag, As, Pb, Cu
Trench: Pb, Au, Ag, Cu, As, Zn
The detected minerals in the profile and trench samples from the three sites are as follows:
Site I: Profile: malachite, chalcopyrite, cerrusite, stibnite and pyrite and cerrusite
Site II: Profile galena, sphalerite, arsenopyrite, chalcopyrite, pyrite, goethite and pyrrhotite pyrite and illmenite
Site III: Profile galena, arsenopyrite, chalcopyrite, pyrite and pyrrhotite and pyrite.
At site I the result of trench samples shows strong significance correlation at p.0.99 between the following pairs of elements:Cu-As, Cu-Ag and As-Pb. Weak significant correlation at p.0.95 occurs between the Paris:Cu-Pb, Cu-Zn and Zn-Pb.The results of profile samples of the same site show strong significant correlation at p.0.99 between the following pairs of elements : As -Sb, As -Pb, Sb -Pb, Zn -Pb and Co-Ni, while weak significant at p.0.95 correlation between Cu -Au and Au – Sb. At site II the correlation coefficient of the profile samples show strong significant at p.0.99 correlation between the following pairs of elements : Sb -Cu, Sb -As, Sb -Au ,Sb-Ni, Cu-As, Cu-Au, As -Au and Pb-Ag and show weak correlation between the following pairs of elements : As -Ni , Ni –Au, Pb –CO, CO- Ag and Zn- Cr. Channel samples show only strong significant correlation at p. 0.99 between copper and lead, while the (r) values of the trench samples show strong correlation between the following pairs of elements : Ag -As, Ag-Pb, Ag-Cu, Zn-Cu and Pb -Cu. At site III the (r) values of trench samples show strong significant at p.0.99 correlation between the following pairs of elements Cu-Pb, Cu-Zn, Cu -Au, Pb-Zn, Pb-As, Pb-Ag, Pb-Au, Zn -Ag ,Zn -Au, Ag-Au, Au-As and Zn-As. Weak significant at p.0.95 correlation appears between Cu-As. The profile samples show strong significant at p.0.99 correlation between the following Paris of elements: As-Zn, As-Cu, As-Sb, Zn-Cu, Zn-Sb, Cu-Ag, Cu-Sb, Ni-CO, Ni-Cr and Co -Cr. Weak significant correlation at p.095 appears between As -Au, Pb -Ag and Ag-Sb.
Mineralization at El samra area is mainly confined to quartz veins, gossans, altered sheared zone, iron bands and pyrite bearing Rhyolite ,hosted in metavolcano -sedimentary rocks (schists and tuffs) and rhyodacitic rocks of Feirani volcanics .
Most of these modes of occurrence of mineralizalion are recorded at the surface and structurally are controlled by several intersected faults , as well as some folding are found. The quartz veins are recorded mainly cutting across the lithic crystal tuffs and chlorite biotite schists. They are found in two forms, as a network of stockwork show tangible Mo mineralization and as small smoky Veinletes rich in iron -oxides cutting across the chlorite biotite schist at sulphide location and show abnormal values in gold mineralization . The gossans are recorded mainly associated with the chlorite biotite schists and the pyrite bearing rhyodacite at Sulphide location and show abnormal values of Au.The altered sheared zones are restricted mainly at Kashm El Fakh area, trending mainly NW-SE and NNE-SSW and show tangible values in Au, Cu and Mo. Banded iron formation is recorded mainly associated with the altered sheared rocks at Khashm El Fakh location. The pyrite bearing rhyolite is recorded in both Sulphide location and Tolihat location. The former one are hosted mainly in rhyodacitic porphyry and shows abnormal values of gold. Mineralogically El samra area contains several varieties of minerals recorded in different mineralized rock units. Most of these minerals are related to shear zones distributed in the investigated locations. The copper mineralization recorded mainly in the shear zones at both Khashm El Fakh and Stockwork locations are represented mainly by chalcopyrite, bornite, chalcocite, digenite, native copper and cuprite. The chalcopyrite displays myrmekitic texture with bornite , while the chalcocite is altered to covellite specially along the grain boundaries and intergrowth with digenite.the native copper is found as fine specks of pink isotropic mineral, partially altered along its cracks to cuprite. Pyrite are mainly recorded in thyolitic dykes at sulphide location, found as anhedral fine crystals disseminated as aggregates, patches with random distribution. Magnetite forming the main bulk in of iron bands, associated with the shear zones at Khashm El Fakh locality, is partially altered to hematite forming martitization texture. The distribution of trace elements in the mineralized rock units at El Samra area reveals that stockwork, tuffs and shear zones at stockwork location are copper bearing associated with high values of molybdenum. The gold and silver are not detected in the most of collected samples. At sulphide location, the distribution of trace elements shows that gold represents the main element in these locations. The highest value of gold is recorded in iron oxides bearing quartz veinlets (5.8ppm), while the gossan and pyrite bearing rhyolite recording averages respectively. The silver is detected in all collected samples, while Cu and Mo show values lesser than those in the stockwork location not exceed 153 ppm and 66.1 ppm respectively. At Khashm El Fakh location the frequency distribution of trace elements clearly indicates that both au and cu are the main elements with associated high values of Ba, Mn, Ti and Mo.
The distribution diagrams the averages of the elements reveal that both Cu and Au show variable distribution, while Mo and Ag show relatively constant distribution a long the shear zones.
The results of the mineralogical investigation of the opaque minerals in rocks of the borehole show that the opaque minerals in the core samples show variable abundance different levels of depth. The main opaque minerals are pyrite, pyrrhotite, arsenopyrite, goethite, hematite, sphalerite, galena, ilmenite, titanomagnetite, chalcopyrite and bornite. The ratio of these minerals ranges from < 1% to 40%. Goethite and hematite minerals disappeared at depth 40.30m (oxidized zone) to the end of the bore-hole. Chlorite biotite schist, chlorite microcline schist, chlorite fluorite schist, mica garnet schist and garnet andalusite schist are represent the main host rocks.Three main mineralized zones are recorded :
Zone I: It includes mainly pyrite pyrrhotite chalcopyrite and arsenopyrite. This zone can be subdivided into two subzones. The first is from depth 26.50m to 29.10m with thickness 2.60m,and includes pyrite, chalcopyrite and arsenopyrite hosted in Chlorite fluorite schist, and form about 8%. The second is started at depth 29.10 m to depth 37.10m with thickness 8.0m, and includes mainly pyrrhotite, hosted In mica garnet schist and form about 2%.
Zone ii: It includes mainly ilmenite and titanomagnetite, forming (6%) and is started from depth 40.30 m to depth 48.12 m with thickness 7.82 m hosted in garnet andalusite schist.
Zone III: It includes mainly sphalarite, galena, arseinopyrite and pyrrhotite (40%), and is started from depth 78.10m to depth 81.15m with thickness 3.05 m. Hosted in chlorite biotite schist.
Geochemical, petrographical and mineralogical investigations were carried out on the core samples raised from the borehole were drilled at site II Umm Zerriq-Kid area, duo to geochemical and geophysical recommendations as are recorded high concentrations of polymetallic deposits (Pb, Zn, Ag, Cu and Au) hosted in altered sheared rocks, gossan and quartz veins at site II recorded to the existence of some conductive bodies at depth ranging from 75 to 85m.The area geologically consists of peleitic schist (mainly chlorite biotite schist and garnet andalusite schist), acidic tuffs intersected by acidic and basic dykes striking N-S. The ore is highly affected by more than one phase of deformation. The mineralizations are restricted mainly in intensely sheared altered rocks conformable with the schistosity including garnetiferous altered rocks, brecciated quartz lenses and iron oxides bearing zones.
- In the light of petrographical, mineralogical and geochemical investigation of the collected core samples the following zones of mineralizations are noticed :
A. Depth from zero to 25.50m (oxidized zone) : It is represented by chlorite biotite schist rich in iron-oxides (hematite - limonite), highly cracked and foliated . The zone is cut across at some depths by milky quartz veinlets. Thin layers of highly silicified garnetiferous altered rocks appear at depth 15m. Goethite, hematite and trace pyrite form the main mineral assemblage in this zone. Clear anomalies of Au, Ag, Zn and Ti are found reached up to 1.8ppm, 67.6ppm, 2100ppm and 1% respectively.
B. Depth from 25.50 m to 29.50 m. : This zone is represented by chlorite microcline fluorite schist, including pyrite, chalcopyrite, goethite, arsenopyrite and hematite. This zone is low concentration of Au, Cu, Pb and Zn recorded but the Ag content shows some anomalies reach up to 17m. At Depth 28m.
C. Depth from 29.50 m to 37m. : The rocks are mica-garnet schist, highly cracked, and banded. The opaque Minerals include; pyrite, chalcopyrite, with high concentration of Ba and Ti and low Cu, Au and Ag contents.
D- Depth from 37.50 m to 51m. : It is represented by garnet-andalusite schist, high specific gravity. This zone includes ilmenite, magnetite and titanomagnetite. It records low concentration in Au, Ag and Zn but Pb content shows some anomalies reach up to 381 ppm. Also the Ba content records high concentrations reaching up to 8000 ppm.
E. Depth from 51 to 77 m. :
The rock is fine to medium grained and consists of garnet andalusite schist with pyrite, chalcopyrite, ilmenite, titanomagnetite, arsenopyrite and pyrrhotite. This zone is characterized by Au anomalies in reaching to 1.2 ppm at depths 52m and 36m. Both Ti and Mn show high concentrations reaching to 2% and 1 % respectfully.
F. Depth from 77m to 82 m. : This zone is considered the most promising mineralized zone. It consists of chlorite biotite schist, highly cracked and well banded containing pyrite, ilmenite, pyrrhotite, arsenopyrite, sphalerite, galena and titanomagnetite. Geochemically this zone shows high concentrations of Zn, Pb, Ag reaching up to 8%, 2 % and 180ppm respectively. It depth 78.5m. Au content shows some anomalies reaching up to 1.8 ppm at depth 79m.
G. Depth from 82 m to100 m. : The rock is very compact garnet andalusite schist containing pyrite, ilmenite, pyrrhotite, arsenopyrite, sphalerite and titanomagenetite. Some anomalies in Pb. And Zn at depth 83m equal to 1187ppm and 2909ppm respectively are recorded. Ti reached up to 1 %.
The zoning coefficient values were calculated and plotted versus the depth of sampling show that the arrangement of the averaging regression lines suggest that zoning sequence of deposition is Au, Cu, Ag, Pb-Zn )