Intersecting fracture geometries in control of geothermal spring occurrences in circumferences of the madra mountain, aegean region of Turkey

Abundant geothermal springs occur in the Aegean Region of Turkey. These are all associated with two important phenomena: 1. Rough topography causing hydrostatic pressure; and 2. Intersecting fracture planes which provide pathways for water to seep down and flow back to the surface upon getting heated. Deep seated steeply dipping fractures which provide inflow in metamorphic or plutonic basement rocks are intersected by young normal faults that are pathways for outflow. Young faults are mainly those bounding horst and graben structures in the region and host hot springs along them. Strike and dip angles of intake and outlet fracture systems control the depth of intersection line where vadose water flow is diverted upward. Temperature is related to intersection depth. Strike direction relationships between the fractures determine if cold water will mix with hot water or not. Once conditions permit hot water to flow to the surface, a convection circulation system forms and alters the regional geothermal gradient by heating along the flow pathway. Geothermal spring temperature is related with regional geothermal gradient but while flowing up cooling does not follow the geothermal gradient because of heating by circulation system developed over the years.