| Abstract |
The exploration process for a geothermal play in western Anatolia was to integrate innovative and classic geothermal exploration techniques to determine exploration slim hole locations. The new method is the use of magmatic, mantle, and radiogenic (MMR) gas exploration method to determine the temperature, relative depth, type of geothermal source and the classic method is detailed structural and petrologic mapping over the area selected by the MMR exploration. The MMR gas exploration method was the first technique used to reduce the size of the geothermal play from forty five square kilometers to an inferred geothermal resource of approximately four square kilometers. The MMR gas sampling and analysis procedure is a shallow invasive geothermal exploration procedure designed to assist in identifying and/or advancing a Geothermal Play to developmental stages of a Geothermal Resource or determining that a geothermal play does not exist. The procedure draws from established work from volcanic research, soil vapor environmental surveys and mineral exploration techniques. The MMR gas survey takes gas samples in suspected Geothermal Play areas from an average depth of one to three meters by using driven soil gas probes and prepared custom samples bottles and/or copper tubes. The collected gas is then analyzed for MMR gases CO2, Ar, CO, N2, He, O2 H2S, H2, CH4, and select gas isotopes. Using gas concentrations, gas ratios and gas isotopes certain factors can be determined to assist in Geothermal Resource identification. The geothermal factors determined are listed below in order of difficulty of interpretation they are as follows: 1. Presence or absence of MMR gases of magmatic origin 2. Differentiation between amagmatic and magmatic source for MMR gases 3. Estimated temperature of thermal energy in place 4. MMR gas quantitative comparisons may indicate areas of effective porosity, either fracture or porous media porosity 5. Geometry and/or location of geothermal source 6. Relative depth to thermal energy in place 7. Grouping or contouring the MMR gas concentrations in conjunction with the above data analysis may provide improved siting for temperature gradient and slim hole/exploration wells and surface geophysical work. The MMR gas survey took 37 gas samples in suspected areas of thermal energy in place. The collected gases were then analyzed for CO2, CH4, CO, He, N2, H2S, O2, and H2 and using comparative gas geothermometers temperatures of potential geothermal sources were determined. The MMR gas exploration method found the highest area of concentration of intermediate to deep MMR Gas temperatures were found in a four square kilometer area in the southeastern area of the Concession and ranged from 107º to 139ºC and 207º to 239ºC respectively. Structural and petrologic mapping was done in detail to pick up where MMR exploration left off specifically identify details in rugged terrain that would further reduce the areas for exploration slim holes. Local lithologies have been mapped as an overlay on the current geologic map such as fault breccia/gouge and abrupt changes in lithology that may indicate offset or dilation. From the field measurements, stereo net projections were performed for a series of joint patterns to determine minor fractures and their association with the major faults trends. The mapping did confirm that the reduced area of the inferred geothermal resource is host to the intersection of two fault sets: (i) NE–SW trending oblique faults and (ii) WNW–ESE trending normal faults. The first fault set was active during Miocene forming/deforming the Selendi Graben and its sedimentary fills; whilst the latter is still active as its southern major conjugate is the Gediz Graben System. Additionally, the world stress map suggests a NW–SE orientation for the youngest tectonic activity (in turn open fractures to transmit fluids) in the region based on two SH azimuth measurements (maximum horizontal stress) of 125 and 101 degrees. |