ABSTRACT In order to determine the composition of brines derived from seawater, studies were carried out on fluid inclusions in evaporites from recent coastal sabkha (halite and gypsum) and Miocene gypsum from the Gulf of Suez. The types of inclusions observed in the studied samples were mainly aqueous-brine, and hydrocarbon bearing inclusions. At room temperature, both types of inclusion occur in monophase, two-phase (L+V), and poly-phase (L+V+S) form. They exist in association and are distributed as primary inclusions throughout the growth zones of chevron and hopper structure of halite, as well as along the growth zones or short lines in gypsum. Hydrocarbon bearing inclusions are dominant in both recent sabkha and Miocene gypsum. No differences were observed between the types and composition of fluid inclusions in gypsum from the recent sabkha and Miocene. Melting behavior and eutectic temperature (Te between –28°C and –33°C) of halite indicated that the salt system was composed mainly of Na ± Ca and/or Mg. In gypsum, eutectic temperature between –47 to – 52 °C were consistent to pure Ca ± Mg chlorides. Salinity, calculated on the basis of final melting temperature of ice (Tmice), hydrohalite melting temperature, and dissolution temperature of daughter crystals, ranged from 22 to 30 wt % NaCl eq., in halite, and from 19 to 26 wt % NaCl eq. in gypsum. The total homogenization temperature (Th) of aqueous – brine inclusions was measured for halite at temperatures between 25°C and 55°C, and for gypsum from 35°C to 75°C. The homogenization temperature of halite (25-55 °C) may represent the surface water temperature, while its range may reflect daily or seasonal variations in temperature. IR investigation confirmed the presence of hydrocabon in the studied samples. Microthermometric measurements of hydrocarbon-bearing inclusions indicated that methane and/or nitrogen are the main organic compounds in the studied samples. Total homogenization temperatures were achieved between 80 and 130 °C. The presence of hydrocarbon-bearing inclusions in the studied samples could be attributed to the existence of oil fields in the Gulf of Suez, possibly a source of organic compounds in the recent Ras Shukeir, and Gebel El-Zeit Middle Miocene evaporites.

ABSTRACT In order to determine the composition of brines derived from seawater, studies were carried out on fluid inclusions in evaporites from recent coastal sabkha (halite and gypsum) and Miocene gypsum from the Gulf of Suez. The types of inclusions observed in the studied samples were mainly aqueous-brine, and hydrocarbon bearing inclusions. At room temperature, both types of inclusion occur in monophase, two-phase (L+V), and poly-phase (L+V+S) form. They exist in association and are distributed as primary inclusions throughout the growth zones of chevron and hopper structure of halite, as well as along the growth zones or short lines in gypsum. Hydrocarbon bearing inclusions are dominant in both recent sabkha and Miocene gypsum. No differences were observed between the types and composition of fluid inclusions in gypsum from the recent sabkha and Miocene. Melting behavior and eutectic temperature (Te between –28°C and –33°C) of halite indicated that the salt system was composed mainly of Na ± Ca and/or Mg. In gypsum, eutectic temperature between –47 to – 52 °C were consistent to pure Ca ± Mg chlorides. Salinity, calculated on the basis of final melting temperature of ice (Tmice), hydrohalite melting temperature, and dissolution temperature of daughter crystals, ranged from 22 to 30 wt % NaCl eq., in halite, and from 19 to 26 wt % NaCl eq. in gypsum. The total homogenization temperature (Th) of aqueous – brine inclusions was measured for halite at temperatures between 25°C and 55°C, and for gypsum from 35°C to 75°C. The homogenization temperature of halite (25-55 °C) may represent the surface water temperature, while its range may reflect daily or seasonal variations in temperature. IR investigation confirmed the presence of hydrocabon in the studied samples. Microthermometric measurements of hydrocarbon-bearing inclusions indicated that methane and/or nitrogen are the main organic compounds in the studied samples. Total homogenization temperatures were achieved between 80 and 130 °C. The presence of hydrocarbon-bearing inclusions in the studied samples could be attributed to the existence of oil fields in the Gulf of Suez, possibly a source of organic compounds in the recent Ras Shukeir, and Gebel El-Zeit Middle Miocene evaporites.

ABSTRACT Surface prospecting for hydrocarbons has been carried out on the gypsum deposits at W.Gasus, W. Syatine, Hamrawein and W.Wizr along the Red Sea coast. Fluid inclusions study recognized the presence of aqueous and hydrocarbon – bearing inclusions. These inclusions are coexisting, and distributed mainly along microfractures of gypsum crystals as secondary inclusions. Primary hydrocarbon bearing inclusions are rare and observed only in Hamrawein gypsum deposits, and are associated with aqueous, and CO2 -bearing inclusions. Microthermometric results of secondary aqueous inclusions indicate that the salt system was composed mainly of Ca ±Mg (as indicated from eutectic temperature). Salinity is low and ranging between 3.39 and 7.17 wt. % NaCl eq. Total homogenization was achieved at temperatures between 75 and 130 C. On the other hand primary aqueous inclusions are higher in salinity (8.86 to13.7 wt. % NaCl eq.), and lower in total homogenization temperature (50 to 70 C) relative to secondary inclusions. Secondary hydrocarbon-bearing inclusions homogenized at temperatures lower than -82.1 C (between -82.5 and -96 C), while the primary inclusions homogenized at temperatures higher than -82.1 C, between -68 and -75 C. Total homogenization was achieved at temperatures between 85 and 126 C in the secondary inclusions and was never achieved in the primary inclusions. In primary CO2– bearing inclusions, the homogenization temperature of CO2 was observed to liquid at temperatures between 25.6 and 30.5 C. IR spectrophotometer investigation lead to the determination of aliphatic chains of C-H, cyano group (C≡N), carbonyl group (-C=O), ethylenic group (C=C) and OH., in addition to heterocompounds of N, S, and O. Chemical analyses of gypsum shows relatively high content of TOC with average ranging from 0.19 to 0.68 wt.%. This in addition to the presence of hydrocarbon fluid inclusions along microfractures as secondary inclusions can prove the presence of microseeps of hydrocarbon from the underlain carbonate rocks

ABSTRACT Surface prospecting for hydrocarbons has been carried out on the gypsum deposits at W.Gasus, W. Syatine, Hamrawein and W.Wizr along the Red Sea coast. Fluid inclusions study recognized the presence of aqueous and hydrocarbon – bearing inclusions. These inclusions are coexisting, and distributed mainly along microfractures of gypsum crystals as secondary inclusions. Primary hydrocarbon bearing inclusions are rare and observed only in Hamrawein gypsum deposits, and are associated with aqueous, and CO2 -bearing inclusions. Microthermometric results of secondary aqueous inclusions indicate that the salt system was composed mainly of Ca ±Mg (as indicated from eutectic temperature). Salinity is low and ranging between 3.39 and 7.17 wt. % NaCl eq. Total homogenization was achieved at temperatures between 75 and 130 C. On the other hand primary aqueous inclusions are higher in salinity (8.86 to13.7 wt. % NaCl eq.), and lower in total homogenization temperature (50 to 70 C) relative to secondary inclusions. Secondary hydrocarbon-bearing inclusions homogenized at temperatures lower than -82.1 C (between -82.5 and -96 C), while the primary inclusions homogenized at temperatures higher than -82.1 C, between -68 and -75 C. Total homogenization was achieved at temperatures between 85 and 126 C in the secondary inclusions and was never achieved in the primary inclusions. In primary CO2– bearing inclusions, the homogenization temperature of CO2 was observed to liquid at temperatures between 25.6 and 30.5 C. IR spectrophotometer investigation lead to the determination of aliphatic chains of C-H, cyano group (C≡N), carbonyl group (-C=O), ethylenic group (C=C) and OH., in addition to heterocompounds of N, S, and O. Chemical analyses of gypsum shows relatively high content of TOC with average ranging from 0.19 to 0.68 wt.%. This in addition to the presence of hydrocarbon fluid inclusions along microfractures as secondary inclusions can prove the presence of microseeps of hydrocarbon from the underlain carbonate rocks

Abstract In the current study, an integration of Enhanced Thematic Mapper Plus (ETM+), field, and laboratory data have been used for lithological mapping of different granitic phases in the Kadabora area, Eastern Desert, Egypt. Application of enhancement techniques, including a new proposed band ratio combination (ratio 5/3, 3/1, 7/5 in RGB, respectively) and supervised classification images are used in discriminating different granitic phases in the Kadabora pluton from each other and from their environs. The data have been proved with the help of field and geochemical investigations. The results revealed that: (1) the Kadabora granitic pluton could be distinguished into three phases that recognized by field and laboratory investigation including granodiorite (phase I), monzogranite (phase II), and syeno-alkali feldspar granite (phase III). These phases are arranged according to their relative ages while the country rocks include ophiolitic mélange and metagabbro–diorite complex. It is also confirmed that the granitic pluton is invaded by dyke swarms which is trending in N–S direction. Geochemically, results show that the granodiorite is calc-alkaline, I-type and formed under subduction tectonic regime. Monzogranite falls within the alkaline and highly fractionated calc-alkaline granites, whereas syeno-alkali feldspar granite extends into proper alkaline granitoids field. Monzogranite and syenoalkali feldspar granite belong to the A2-subtype granite. This A2-subtype granite was probably formed in an extensional regime, subsequent to subduction which can lead to tensional break-up of the crust (i.e., post-collisional, post-orogenic granites). The monzogranite and the syenoalkali feldspar granite were probably formed by partial melting of relatively anhydrous lower crust source and/or tonalite to granodiorite is viable alternative to the granulite source.

Geochemistry and fluid inclusions studies were carried out on garnet and beryl from Quaternary alluvium deposits of Meluli-Namuhuca area, Mozambique. Garnet occurs as euhedral large crystals and is commonly brownish red, with a moderate brown hue in transmitted light. Apatite and ilmenite are the common inclusions. Geochemically, garnet is characterized by nearly homogenous chemical composition with Pyr (46.72-48.35), Alm (39.77-48.35), Gr (10.03-10.56) and Sps (1.14-1.31) mol %. This garnet is referred to as iron-rich pyrope or pyrope – almandine. Chemical compositions reflect their crystallization from magma (Mg-Fe isomorphism).The high-Mg, and low Na of the studied garnet are consistent with high temperature eclogitic garnet associated with diamond. Fluid inclusions study indicates that garnet was deposited from high saline and high temperature fluids. Beryl is present as euhedral hexagonal crystals with different color (green emerald, blue aquamarine, and yellow heliodors). It enclosed cassiterite, wolframite and barite micro-inclusions, which support that the studied beryl is connected to hydrothermal ore-bearing fluids. Fluid inclusions study reveal that beryl was deposited due to boiling process of medium salinity (9-12 wt.% NaCl eq.), and medium temperature (180-240 °C) fluids. Pressure of trapping was estimated between 400 and 700 bars.

Geochemistry and fluid inclusions studies were carried out on garnet and beryl from Quaternary alluvium deposits of Meluli-Namuhuca area, Mozambique. Garnet occurs as euhedral large crystals and is commonly brownish red, with a moderate brown hue in transmitted light. Apatite and ilmenite are the common inclusions. Geochemically, garnet is characterized by nearly homogenous chemical composition with Pyr (46.72-48.35), Alm (39.77-48.35), Gr (10.03-10.56) and Sps (1.14-1.31) mol %. This garnet is referred to as iron-rich pyrope or pyrope – almandine. Chemical compositions reflect their crystallization from magma (Mg-Fe isomorphism).The high-Mg, and low Na of the studied garnet are consistent with high temperature eclogitic garnet associated with diamond. Fluid inclusions study indicates that garnet was deposited from high saline and high temperature fluids. Beryl is present as euhedral hexagonal crystals with different color (green emerald, blue aquamarine, and yellow heliodors). It enclosed cassiterite, wolframite and barite micro-inclusions, which support that the studied beryl is connected to hydrothermal ore-bearing fluids. Fluid inclusions study reveal that beryl was deposited due to boiling process of medium salinity (9-12 wt.% NaCl eq.), and medium temperature (180-240 °C) fluids. Pressure of trapping was estimated between 400 and 700 bars.

Abstract The Neoproterozoic granite of Gabal Abu Diab, central Eastern Desert of Egypt, comprises mainly garnetbearing granite and alkali feldspar granite intruded into calc-alkaline granodiorite–tonalite and metagabbro–diorite complexes. The garnet-bearing granite is composed mainly of plagioclase, K-feldspar, quartz, garnet and primary muscovite ± biotite. The presence of garnet and primary muscovite of Abu-Diab granite suggests its highly fractionated character. Geochemically, the garnetbearing granite is highly fractionated as indicated from the high contents of SiO2 (74.85–77.5%), alkalis (8.27 to 9.2%, Na2O+K2O) and the trace elements association: Ga, Zn, Zr, Nb and Y. This granite is depleted in CaO, MgO, P2O5, Sr and Ba. The alumina saturation (Shand Index, molar ratio A/CNK) of 1.0 to 1.1 indicates the weak peraluminous nature of this garnet-bearing granite. The geochemical characteristics of the Abu Diab garnetbearing granite are consistent with either the average I-type or A-type granite and also suggest post-orogenic or anorogenic setting. A fluid inclusions study reveals the presence of three fluid generations trapped into the studied granite. The earlier is a complex CO2–H2O fluid trapped in primary fluid inclusions with CO2 contents >60 vol.%. These inclusions were probably trapped at minimum temperature >400°C and minimum pressure >2 kb. The second is immiscible water–CO2 fluid trapped in secondary and/or pseudo-secondary inclusions. The trapping conditions were estimated at temperature between 400°C and 170°C and pressure between 900 and 2000 bar. The latest fluid is low-salinity aqueous fluid trapped in secondary two-phase and mono-phase inclusions. The trapping conditions were estimated at temperature between 90°C and 160°C and pressure 900 bar. The origin of the early fluid generation is magmatic fluid while the second and third fluids are of hydrothermal and meteoric origin, respectively.

Abstract The Neoproterozoic granite of Gabal Abu Diab, central Eastern Desert of Egypt, comprises mainly garnetbearing granite and alkali feldspar granite intruded into calc-alkaline granodiorite–tonalite and metagabbro–diorite complexes. The garnet-bearing granite is composed mainly of plagioclase, K-feldspar, quartz, garnet and primary muscovite ± biotite. The presence of garnet and primary muscovite of Abu-Diab granite suggests its highly fractionated character. Geochemically, the garnetbearing granite is highly fractionated as indicated from the high contents of SiO2 (74.85–77.5%), alkalis (8.27 to 9.2%, Na2O+K2O) and the trace elements association: Ga, Zn, Zr, Nb and Y. This granite is depleted in CaO, MgO, P2O5, Sr and Ba. The alumina saturation (Shand Index, molar ratio A/CNK) of 1.0 to 1.1 indicates the weak peraluminous nature of this garnet-bearing granite. The geochemical characteristics of the Abu Diab garnetbearing granite are consistent with either the average I-type or A-type granite and also suggest post-orogenic or anorogenic setting. A fluid inclusions study reveals the presence of three fluid generations trapped into the studied granite. The earlier is a complex CO2–H2O fluid trapped in primary fluid inclusions with CO2 contents >60 vol.%. These inclusions were probably trapped at minimum temperature >400°C and minimum pressure >2 kb. The second is immiscible water–CO2 fluid trapped in secondary and/or pseudo-secondary inclusions. The trapping conditions were estimated at temperature between 400°C and 170°C and pressure between 900 and 2000 bar. The latest fluid is low-salinity aqueous fluid trapped in secondary two-phase and mono-phase inclusions. The trapping conditions were estimated at temperature between 90°C and 160°C and pressure 900 bar. The origin of the early fluid generation is magmatic fluid while the second and third fluids are of hydrothermal and meteoric origin, respectively.