MONITORING OF CHEMICAL AND ISOTOPIC COMPOSITIONS OF

155 Pages·2004·4.75 MB·English

MONITORING OF CHEMICAL AND ISOTOPIC COMPOSITIONS
OF GEOTHERMAL WATERS ALONG
THE NORTH ANATOLIAN FAULT ZONE

A THESIS SUBMITTED TO
THE GRADUATE SCHOOL OF NATURAL AND APPLIED SCIENCES
OF
MIDDLE EAST TECHNICAL UNIVERSITY

BY

SELİN SÜER

IN PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR
THE DEGREE OF MASTER OF SCIENCE
IN
GEOLOGICAL ENGINEERING

SEPTEMBER 2004

ABSTRACT

MONITORING OF CHEMICAL AND ISOTOPIC COMPOSITIONS
OF GEOTHERMAL WATERS ALONG
THE NORTH ANATOLIAN FAULT ZONE

Süer, Selin
M. S., Department of Geological Engineering
Supervisor: Prof. Dr. Nilgün Güleç

September 2004, 140 pages

This study aims to determine the chemical (anion-cation) and isotopic
compositions (δ18O-δD-3H) of the geothermal waters along the North Anatolian
Fault Zone (NAFZ) and highlight any possible seismicity-induced temporal
variations during the course of two years (2002-2003) monitoring programme.
The geothermal sites are alligned along a 800 km transect of the NAFZ and are,
from west to east, Yalova, Efteni, Bolu, Mudurnu, Seben, Kurşunlu,
Hamamözü, Gözlek and Reşadiye.
The thermal waters of NAFZ are dominantly Na-HCO , whereas the
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cold waters are dominantly Ca-HCO in character. The highest temperature
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(72.3°C) is recorded in Seben. The hot waters are slightly acidic to alkaline in
character with pH values ranging between 5.92-7.97, while the cold waters are
comparatively more alkaline with pH values between 6.50-8.83.
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Both hot and the cold waters are meteoric in origin. The hot waters have
lower δ18O-δD and tritium values suggesting higher recharge altitudes for
aquifers and longer residence times for waters, respectively, in the geothermal
system (compared to the cold waters).
Temporal variations are detected in both ionic and isotopic
compositions of the cold and the hot waters, and these reflect seasonal
variations for cold and seismicity-induced variations for hot waters. Although
no major earthquakes (M>5) occurred along the NAFZ during the monitoring
period, temporal variations recorded in Cl and 3H, and to a lesser extent in Ca
and SO contents seem to correlate with seismicity along the NAFZ. In this
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respect, Yalova field deserves the particular attention since seismicity induced
variations were better recorded in this field.

Keywords: North Anatolian Fault Zone, Seismicity, Geothermal Waters,
Isotopes, Chemical Composition

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ÖZ

KUZEY ANADOLU FAY HATTINDAKİ JEOTERMAL SULARIN
KİMYASAL VE İZOTOPİK BİLEŞİMLERİNİN İZLENMESİ

Süer, Selin
Yüksek Lisans, Jeoloji Mühendisliği Bölümü
Tez Yöneticisi: Prof. Dr. Nilgün Güleç

Eylül 2004, 140 sayfa

Bu çalışma, Kuzey Anadolu Fay Hattı (KAFH) boyunca yer alan
jeotermal suların, kimyasal (anyon-katyon) ve izotopik (δ18O-δD-3H)
bileşimlerinin belirlenmesini ve olası zamansal değişimlerinin, 2 yıllık izleme
çalışması (2002-2003) süresince, sismik etkinlikler ile ilişkilendirilmesini
amaçlamaktadır. Jeotermal sahalar Kuzey Anadolu Fayının 800 km’lik bir hattı
boyunca yer almaktadır ve bunlar batıdan doğuya doğru Yalova, Efteni, Bolu,
Mudurnu, Seben, Kurşunlu, Hamamözü, Gözlek ve Reşadiye sahalarıdır.
KAFH’ nın termal suları egemen olarak Na-HCO soğuk suları ise
3,
egemen olarak Ca-HCO karakterindedir. En yüksek sıcaklık (72.3°C) Seben
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sahasında kaydedilmiştir. Sıcak sular, 5.92-7.97 arasında değişen pH değerleri
ile hafif asidikten baziğe doğru eğilim gösterirken, soğuk sular 6.50-8.83
arasında değişen pH değerleri ile daha baziktir.
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Hem sıcak hem de soğuk sular meteorik kökenlidir. Sıcak suların, soğuk
sulara oranla daha düşük δ18O-δD ve tritium değerlerine sahip olması jeotermal
sistemdeki akiferlerin daha yüksek seviyelerden beslendiğine ve suların yeraltı
dolaşım sürelerinin uzun olduğuna işaret etmektedir (soğuk sularla
karşılaştırıldığında).
Zamansal değişimler, soğuk ve sıcak suların, hem iyonik hem izotopik
bileşimlerinde izlenmektedir ve bunlar, soğuk sular için mevsimsel değişimleri,
sıcak sular için ise sismisite-bağımlı değişimleri yansıtmaktadır. İzleme süresi
boyunca KAFH’ nda önemli (M>5) depremler olmamasına rağmen, Cl, 3H ve
bir ölçüye kadar da Ca ve SO bileşimlerinde kaydedilen zamansal değişimler,
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KAFH boyunca gerçekleşen sismik etkinlikler ile deneşmektedir. Bu bağlamda,
Yalova sahası, sismisiteye bağlı değişimlerin daha iyi kaydedilmesinden dolayı
özel önem arz etmektedir.

Anahtar Kelimeler: Kuzey Anadolu Fay Hattı, Sismisite, Jeotermal Sular,
İzotoplar, Kimyasal Kompozisyon
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ACKNOWLEDGMENTS

I would like to express my sincere gratitude to Prof. Dr. Nilgün Güleç, the
supervisor of this study, for her technical support, guidance, criticism and
encouragement throughout the research.

I would also like to thank Assoc. Prof. Dr. Halim Mutlu for his help at various
stages of the thesis study.

Thanks are extended to the Isotope Laboratory of the Technical Research
Quality Control Department of the Turkish State Hydraulic Works for their
support with the isotope analyses.

This study was supported by the TUBİTAK YDABAG-100Y097 project.

I would also like to thank Dr. Fatma Toksoy Köksal, Jülide Yapmış and
Şebnem Ökten for their support during this thesis study.

Finally, I am appreciative to my parents for their encouragement throughout the
thesis study.
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TABLE OF CONTENTS

PLAGIARISM.................................................................................... iii
ABSTRACT………………………………………………………... iv
ÖZ…………………………………………………………………... vi
ACKNOWLEDGEMENTS………………………………………… viii
TABLE OF CONTENTS……………………………………...…..... ix
LIST OF TABLES………………………………………………….. xi
LIST OF FIGURES……………………………………………........ xii
CHAPTERS
1. INTRODUCTION……………………………………………...... 1
1.1. Purpose and Scope………………………………………...… 2
1.2. Materials and Methods………………………………………. 2
1.3. Layout of Thesis…...……………...…………………………. 5
2. CHEMICAL AND ISOTOPIC TECHNIQUES IN
GEOTHERMAL INVESTIGATION: AN OVERVIEW…………... 7
2.1. Chemical Components of Geothermal Fluids……………….. 7
2.2. Environmental Isotopes in Geothermal Investigation……...... 9
2.2.1. Oxygen and Hydrogen Isotopes………………………... 10
2.2.2.Tritium………………………………………………….. 14
2.3. Geothermal Fluid Compositions as Seismic Precursors…….. 18
3. THE NORTH ANATOLIAN FAULT ZONE: TECTONIC
SETTING AND RECENT SEISMIC ACTIVITIES……………….. 24
3.1. Tectonic Setting……………………………………………... 24
3.2. Recent Seismic Activities…………………………………… 25
4. GEOTHERMAL FIELDS ALONG NAFZ……………………… 33
4.1. Geologic Setting and Regional Geology….............................. 33
4.2. Geologic and Hydrogeologic Outline of Geothermal Fields... 35
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4.2.1. Efteni-Gölyaka…………………………………………. 35
4.2.2. Yalova-Termal…………………………………………. 36
4.2.3. Bolu-Town Center……………………………………... 38
4.2.4. Mudurnu-Babas (Bolu)……………………………….... 39
4.2.5. Seben-Kesenözü (Bolu)………………………………... 42
4.2.6. Hamamözü-Amasya…………………………………..... 44
4.2.7. Gözlek-Amasya ……………………………………....... 46
4.2.8. Reşadiye-Tokat ………………………………………... 50
4.2.9. Kurşunlu-Çankırı …………………………………….... 52
5. METHODS OF STUDY…………………………………………. 55
5.1. Sampling…………………………………………………….. 55
5.2. Analytical Techniques………………………………………. 62
6. HYDROGEOCHEMICAL CHARACTERISTICS…………….... 64
6.1. Results of Chemical Analyses……………………………….. 64
6.2. Hydrogeochemical Facies…………………………………… 75
7. ISOTOPIC COMPOSITIONS………………………………….... 83
7.1. Oxygen and Hydrogen Isotopes……………………………... 83
7.2. Tritium Contents…………………………………………….. 85
8. TEMPORAL VARIATIONS AND RELATION TO
SEISMICITY……………………………………………………….. 99
8.1. Temporal Variations in Temperature and pH Values……….. 99
8.2. Temporal Variations in Chemical Compositions……………. 103
8.3.Temporal Variations in Oxygen-18 and Deuterium
Compositions………………………………………………… 111
8.4. Temporal Variations in Tritium Contents………………….... 114
8.5. Comparison of Thermal Waters From Springs and Wells…... 116
8.6. Concluding Remarks……………………………………….... 123
9. CONCLUSIONS AND RECOMMENDATIONS………………. 127
REFERENCES……………………………………………………… 131

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