|
Geothermal Potential in the Structural Domain of the HinduKush
in Afghanistan
Geological Structure:
In the earth, a certain amount of heat is generated by
friction, as well as by other sources, at the boundaries of the
crustal plates. The structure of Afghanistan is the result of
accretion of such colliding Gondwanan micro plates or fragments
onto the margins of Eurasia (Tapponnier, et al., 1981) along the
Herat-Panjshir E-W striking geo suture, which is a deep seated
strike-slip fault, dipping as deep as up to 700 kilometer into
the mantle. This major structural fault and fracture system in
Afghanistan facilitates the percolation of water into the
superheated zones in the crust to produce geothermal fluids.
Similar structures along the Chaman-Moqor NE-SW striking
fault system, the Sarobi-Altimore NE-SW arcuate fault system,
and other secondary faults throughout Afghanistan cover most of
the regions of this country (Figure 2), where hot springs are
the surface indication of geothermal energy resources associated
with them.
Neotectonic movements in Afghanistan generated by
collisional events since the end of the Cretaceous some 65
million years ago, resulted in the uplifting of the HinduKush
mountain ranges that extend from the north-easternmost corner of
the country in Badakhshan province in a NE-SW-W direction up to
the westernmost border of the country in Herat province,
dividing the whole structure of Afghanistan into northern and
southern structural components (Saba and Avasia, 1995a). Recent
tectonic movements are characterized by seismic and geothermal
activities all over the country. The dynamic characters of the
resulting structures indicate north-south compression and
east-west extension. In addition, neotectonic movements show
strong vertical uplifting, total rising and differential
tilting. Seismic activities in Afghanistan show a decreasing
tendency from east to west, with the strongest seismic activity
occurring in the northeaster Badakhshan province, where the most
active structures of the country are located
Figure 2. Surface Indications of Geothermal Prospects of
Afghanistan.
(Map shows thermal waters with a surface T of more than
20.C)
major geothermal manifestations are located
along the Herat-Panjshir geo suture and the Chaman-Moqor fault
systems in central Afghanistan active terrain Geothermal
manifestations in these areas are mostly marked in the fracture
systems of active faults, within graben or half graben basins
and linear faulted valleys or wide valleys of the southern
structural component of Afghanistan.
(Figure 3).
Figure 3. Neotectonic activity in the HinduKush resulting
in dramatic uplift and displacement of the crust, as viewed in this photo of the Bande-Azhdar,
Bamiyan, in central Afghanistan. Hydro geochemistry of Thermal
Waters in Afghanistan
Figure 4. The Obe Shefa (healing) hot spring, Obe Township,
120 km to the east of Herat city, with a surface temperature of
52.C and a very hot ground in a granitic contact zone.
Figure 5. Southerly view of the Kalu Valley, 20 km to the
east of Bamiyan Township, with may hot spring manifestations,
seen here to the left of the Kalu River.
Geothermal Energy For Electricity Production:
geothermal energy reserves in Afghanistan could
provide part of the electricity needs required to satisfy the
demand. Electrical power production is the most profitable use
of geothermal energy, and worldwide has grown the most,
comparing to other geothermal applications. Electricity is
produced with geothermal steam in 21 countries, with the USA
being the top producer in 1999, producing 2228 MWe. In the
Philippines, about 22% of the electricity is generated with
geothermal steam. Other countries presently generating 10-20% of
their electricity with geothermal energy are Costa Rica, El
Salvador, Iceland and Nicaragua (Huttrer, 2001). Currently many
developing countries such as Turkey, Kenya, Taiwan, Chile, and
Tibet in China are also developing their geothermal fields.
To generate electricity from geothermal hot water, two
prerequisites are required to be fulfilled: adequate technology,
and an abundant high-temperature water or steam. At present,
efficient and durable technology is readily available to
Afghanistan to produce low-cost electricity from its geothermal
resources. At the meantime, the tectonic structure of
Afghanistan suggests the presence of vast hot water circulation
systems underground. But only under certain conditions of depth,
temperature, and chemistry does it pay to drill into these
systems, conditions that require further explorations to be
undertaken.
Geothermal Energy for Direct Uses:
Direct-use geothermal technologies use naturally hot
geothermal water for commercial applications. Afghans know the
medicinal and healing properties of hot water springs,
especially its therapeutic power for skin conditions and
rheumatic arthritis. Medicinal bathing or balneology is an
important sector to be considered for modern developments of
some of the well-know healing hot springs of the country. This
has the potential to contribute to the improvement of life
standard and the overall well being of the people of
Afghanistan, while creating hundreds of new and permanent jobs.
|
