Náttúrufræðingurinn - 1984, Page 84

syni flyt ég mínar bestu þakkir fyrir
samstarfið um rannsókn jarðhitasvæð-
isins á Reykjum, Auði Ágústsdóttur,
tækniteiknara, fyrir frágang mynda og
ritstjóra Náttúrufræðingsins, Helga
Torfasyni, fyrir að koma enska úr-
drættinum á skiljanlegt mál.
HEIMILDIR
Axel Björnsson. 1980. Jarðhitaieit & rann-
sókn jarðhitasvæða með jarðeðlisfræði-
legri könnun. — Náttúrufræðingurinn
50, 3-4: 227-249.
Axel Björnsson & Kristján Sæmundsson.
1975. Jarðhiti í nágrenni Akureyrar. —
Orkustofnun, OS JHD 7557, 53 bls.,
Reykjavík.
Kristján Sæmundsson & Ingvar Birgir
Friðleifsson. 1980. Jarðhiti og jarð-
fræðirannsóknir. — Náttúrufræðingur-
inn 50, 3-4: 157-188.
Ólafur G. Flóvenz, Ásgrímur Guðmunds-
son, Kristján Sæmundsson & Sigbjörn
Kjartansson. 1982. Reykir í Fnjóska-
dal. Yfirborðsrannsóknir og rann-
sóknarboranir árið 1980. - Áfanga-
skýrsla nr.2. Orkustofnun, OS82050/
JHD08, 43 bls., Reykjavík.
Stefán Arnórsson. 1980. Jarðefnafræði og
jarðfræðirannsóknir. — Náttúrufræð-
ingurinn 50, 3-4: 206-226.
Sveinbjörn Björnsson. 1980. Jarðhiti,
grunnvatn og varmi. — Náttúrufræð-
ingurinn 50, 3—4: 271—293.
Valgarður Stefánsson. 1980. Borun eftir
jarðhita og rannsóknir á borholum. -
Náttúrufræðingurinn 50, 3-4: 333—
359.
SUMMARY
The geothermal area
at Reykir in Fnjóskadalur,
northern Iceland
by
Ólafur G. Flóvenz
National Energy Authority
Grensásvegur 9
108 Reykjavík
In the low temperature geothermal area
Reykir in Fnjóskadalur valley, northern
Iceland, approximately 5 1/s of 90° hot
water ascend to the surface. The valley
floor is covered by 20—30 m thick alluvial
sediments through which the water flows
to the surface. In the winter scene in fig.l
it is clear how the snow melts around the
hot springs.
In the geological map (fig.3) the most
obvious structural trend is in the NNE
striking normal fault and dykes. A less
impressive trend is in the flexure zone
striking N-S. The third and least obvious
trend is in dykes striking NW—SE, and
only two dykes with this orientation are
observed.
Resistivity surveys indicate very low
resistivity in the bedrock below the hot
spring area, indicating high porosity. The
low resistivity forms an elongated body
along the NNE-striking fault and dyke
zone (fig.4).
The temperature distribution at 0.5 m
depth was mapped out in the soil around
the hot springs. A thermal anomaly strik-
ing NNE was found (fig. 5). A self potenti-
al anomaly was observed having the same
direction. By comparing these measure-
ments with the resistivity survey, it seems
most likely that the aquifers are related to
the NNE striking structures which dip is
90° +/- 10°.
In order to locate the aquifer leading the
hot water to the surface, and to get esti-
mate of its geometry, some six wells were
drilled, 100—200 m deep. The wells were
drilled along a line perpendicular to the
NNE structural trend. From temperature
measurements in the wells a thermal mod-
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