Determination of Curie Point Depth and Heat Flow Using Airborne Magnetic Data over the Kom-Ombo and Nuqra Basins, Southern Eastern Desert, Egypt

The Kom-Ombo and Nuqra basins in southern Egypt have recently been discovered as potential hydrocarbon basins. The lack of information about the geothermal gradient and heat flow in the study area gives importance to studying the heat flow and the geothermal gradient. Several studies were carried out to investigate the geothermal analyses of the northwestern desert, as well as the west and east of the Nile River, using density, compressive wave velocity, and bottom hole temperature (BHT) measured from deep oil wells. This research relies on spectral analysis of airborne magnetic survey data in the Kom-Ombo and Nuqra basins in order to estimate the geothermal gradient based on calculating the depth to the bottom of the magnetic source that caused the occurrence of these magnetic deviations. This depth is equal to the CPD, at which the material loses its magnetic polarisation. This method is fast and gives satisfactory results. Usually, it can be applied as a reconnaissance technique for geothermal exploration targets due to the abundance of magnetic data. The depth of the top (Zt) and centroid (Z0) of the magnetic source bodies was calculated for the 32 windows representing the study area using spectral analysis of airborne magnetic data. The curie-isotherm depth, geothermal gradient, and heat flow maps were constructed for the study area. The results showed that the CPD in the study area ranges from 13 km to 20 km. The heat flow map values range from 69 to 109 mW/m2, with an average of about 80 mW/m2. The calculated heat flow values in the assigned areas (A, B, C, and D) of the study area are considered to have high heat flow values, reaching 109 mW/m2. On the other hand, the heat flow values in the other parts range from 70 to 85 mW/m2. Since heat flow plays an essential role in the maturation of organic matter, it is recommended that hydrocarbon accumulations be located in places with high heat flow values, while deep drilling of hydrocarbon wells is recommended in places with low to moderate heat flow values.

Depth and Structural Parameters Determination of the Sedimentary Basin in Atmur Nuqra Area, South Eastern Desert, Egypt Using Aeromagnetic Data Analysis

The study area is located at the south of the eastern desert of Egypt between latitudes 24°N to 25°N and longitudes 33°E to 33°50'E covering an area of about 9407 km2. The study area is mainly covered with sediments whose age extends from the upper Cretaceous to the Quaternary, in addition to the presence of some basement rocks such as younger granites, metasediments and metagabbro. The research aims essentially to determine the thickness of the sedimentary basin by determining the depth to the top of basement and delineating the subsurface geological structures which affected this sedimentary basin. The Euler depth map exhibited that the north parts of the area have shallow depth values from 1000 m to 2000 m. The southern parts also show a shallow to moderate depths ranging from 1000 m to 2400 m. The deepest parts are located at the middle and at the western parts and are ranging in value from 3000 m to more than 4000 m. The horizontal derivative and tilt derivative techniques proved that the most effective trends all over the study area are NW-SE and NE-SW directions as mentioned in geologic lineaments map. The basement tectonic map shows clearly all the faults affected the area. It shows that there are many high blocks trending mainly in NW-SE and NE-SW directions. All high blocks surround a large sedimentary basin reaches depth of about more than 4000 m. All the results produced from 2D-modeling illustrate that the sedimentary basinal area (G2) is the deeper basin all over the area and it is controlled by some faults and fractures. 3D inversion was used and resulted in that the area of study have many high blocks at shallow to moderate depths which surrounding a large sedimentary basinal area with very deep depth values. All the techniques which applied in this research led to that the largest sedimentary basin is located at the center of the study area with NW-SE trend and depth value of about 4000 m.

Geology and geochemistry of the granitic rocks and associated dykes,East Gabal Nuqra,South Eastern Desert,Egypt

A crescent-shape granitic stock and associated dykes is located to the East Gabal Nuqra at the extreme western part of Wadi Natash,South Eastern Desert,Egypt.The examined granites are classified as alkali-feldspar granites and mainly consist of quartz,potash feldspars,plagioclases,and aegirine-augite.Xenotime,zircon,apatite and allanite are accessories representing the source of Y,U,Th and REEs in these rocks.These granites are characterized by high K2O,Na2O and Zn contents and Rb/Sr ratio.Also,they are highly enriched in high field strength elements(HFSE),especially Zr(1529×10-6),Nb(100×10-6),Hf(91×10-6) and Y(624×10-6) and light rare-earth elements(LREE,141×10-6) concentrations and strongly depleted in Ca,Mg,Sr and Eu contents.These features suggest that they are similar to A-type granites(type-2).The rhyolite dykes and granites have similar geochemical characteristics whereas the chondrite-normalized REE patterns show a LREE enriched feature with strong negative Eu-anomaly,whereas the REE pattern of trachydacites show slightly fractionated pattern with no Eu-anomaly.It is suggested that the trachydacites were generated by small degree of partial-melting deep-seated basic source.Such liquid,when subjected to fractional crystallization involving separation of plagioclases as residue,generated the alkali-feldspar granites.And further fractional crystallization gave rise to the alkali rhyolites.The igneous rock suite originated from metaluminous to alkaline trachytic magma,and was developed in a within-plate tectonic environment.The extension caused by NW-SE right-lateral shear in area led to the emplacement of the alkali-feldspar granites.The later extrusion of the alkali rhyolite and trachydacite dykes was due to cauldron subsidence.