Geology, geologic structure, and hot springs in southern...

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,腋腄腇腂腊腆腊腆腅腉腁腃腈 Geology, geologic structure, and hot springs in southern Kyushu, Japan 膰臩臅臘 + 臥臤 , 臝膵 +3 0 +- 臐膬臗臝膵 +3 0 +. 臐膬臧+ 膩膧臇膽腽臧腽臚臀膊膂膋腷腽腷 23***0/ 膩膧臇膦膏膖 +,+-/ , 膩膧臇膕膒膡臠臚 23*2/00 膩膧臇膦膀臁膱臂 +*+ Tetsuo KOBAYASHI + and Toru YANO , + Earth and environmental Sciences, Faculty of Science, Kagoshima University +,+-/, korimoto, Kagoshima 23***0/, Japan , Kagoshima Prefectural Police +*+, Kamoike-shinmachi, Kagoshima 23*2/00, Japan Abstract The geology, geologic structure, and hot springs in southern Kyushu are discussed in this paper. The basement rocks of this area are composed mainly of the sedimentary complexes of the Shimanto Terrane which is divided into two groups : Cretaceous North- ern Shimanto Terrane and Tertiary Southern Shimanto Terrane. The graben structures in southern Kyushu have been formed in relation to the opening of the Okinawa Trough since ca. +* Ma, and followed by contemporaneous volcanism. Volcanism was most active in between . Ma and , Ma which formed the fundamental graben structure such as Hoku- satsu Triangular Graben, Hitoyoshi basin, and Kagoshima Graben. Since , Ma, the volcan- ism within the Kagoshima Graben became most active involving at least three calderas : Ata, Aira, and Kakuto calderas from south to north. Active volcanoes also exist in this graben, indicating an active volcano-tectonic depression. Most hot springs in southern Kyushu are distributed in these grabens, suggesting an intimate genetic relation between volcanism and hot springs. The heat supply of the hot springs from the basement rocks is sourced not only from the present magma, but also from Tertiary granites. Key words : Shimanto Terrane, Kagoshima Graben, Hokusatsu Triangular Graben, Okinawa Trough, hot spring 臎膌膭腙臀膪臀膪膛膹腙膑膵腖腴膷腙膄膐腣腺膃腎腑臎膌膭腙膆臖膅臫腚膫腘膥臢膮自 膸膎腕腆腟臓腬膇腙臟膼腖膾膣膇腙臎膼腘臏臛腍腡腠臎膌膭腙臀膜膛膹腚+* Ma 腯膞腙 腳臍腧腪腨腙膑膵腻膽腖膄臭腎腔膑膵腍腡腑膿臬腲臊腙膲膝腘腓腡腸膤腾臊腜腾臔腵腎臋腘 . Ma, Ma 腚腸膤腾臊腊膟腜膓腎腋腉腓膚腰腘腢腑腒腔腇腑腐腙腹臃腕臟膢膣腼臀 膜腝膳膈臡臀腍腞腘腚膩膧臇臀膜腙膗膑腊膑膵腍腡腑, Ma 腯膞腚膩膧臇臀膜臌臚腕腙腸膤 腾臊腊腾臔腕腆腟臎腉腞腭膻腮臨腶膉臉腤腫腦腪臈腊臜腸腣膍腟臞腎腑腛腑腾腸膤腜 臀膜臌腘膺膠腎腔腈腟膩膧臇臀膜腚膙膠腕腜腾臊臄腗腸膤膛膹膴臀膜腕腆腠腴膷腙膽臕腚膩膧臇臀膜腖臟膢膣腼臀膜腙臌臚腘臛臙腎腔腈腟腴膷腊腸膤腾臊腙臑腖臣膶 腗膵腱膄膐腘腆腠腌腖腣膨腎腔腇腠腛腑膆臖膅腉腞臦膯腏腠腴膷腙臑膘腜膙膠腙腩腥腩腉 /1 ,**111

Transcript of Geology, geologic structure, and hot springs in southern...

Page 1: Geology, geologic structure, and hot springs in southern ...j-hss.org/journal/back_number/vol57_pdf/vol57no1_011_029.pdf · The geology, geologic structure, and hot springs in southern

,� ������������Geology, geologic structure, and hot springs in southern

Kyushu, Japan

����+� �� �,

� +3� 0 +-���� � +3� 0 +.����

+��������������� �23*�**0/ ���� ! +�,+�-/,���"#$%� �23*�2/00 ����&'() +*�+

Tetsuo KOBAYASHI+ and Toru YANO

,

+ Earth and environmental Sciences, Faculty of Science, Kagoshima University

+�,+�-/, korimoto, Kagoshima 23*�**0/, Japan, Kagoshima Prefectural Police +*�+, Kamoike-shinmachi, Kagoshima 23*�2/00, Japan

Abstract

The geology, geologic structure, and hot springs in southern Kyushu are discussed in

this paper. The basement rocks of this area are composed mainly of the sedimentary

complexes of the Shimanto Terrane which is divided into two groups : Cretaceous North-

ern Shimanto Terrane and Tertiary Southern Shimanto Terrane. The graben structures

in southern Kyushu have been formed in relation to the opening of the Okinawa Trough

since ca. +* Ma, and followed by contemporaneous volcanism. Volcanism was most active

in between . Ma and , Ma which formed the fundamental graben structure such as Hoku-

satsu Triangular Graben, Hitoyoshi basin, and Kagoshima Graben. Since , Ma, the volcan-

ism within the Kagoshima Graben became most active involving at least three calderas :

Ata, Aira, and Kakuto calderas from south to north. Active volcanoes also exist in this

graben, indicating an active volcano-tectonic depression.

Most hot springs in southern Kyushu are distributed in these grabens, suggesting an

intimate genetic relation between volcanism and hot springs. The heat supply of the hot

springs from the basement rocks is sourced not only from the present magma, but also

from Tertiary granites.

Key words : Shimanto Terrane, Kagoshima Graben, Hokusatsu Triangular Graben,

Okinawa Trough, hot spring

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,� ����� ��,-.56��89� +,*** km4�2��� ��� )��������'�����2�/�L��P@A��� �q�!�2�� ���� ¡¢��%&���£¤�� ¥¦�PQTU�56P��§��:P6� ^�¨L�2�pb3� �62%&'():©�@A�� ZFig. +\�s�ª©��a«¬�Y/2� '­(�®�¯�°� Z£¤± \ ��/¢²�P³´�a:µuI� Z¶·� +30/\� s�Y/PaNO�� %&'()�¸ �¹�@Aº»�q��������

Fig. + Geologic and structural map of the Ryukyu arc, Okinawa Trough, Taiwan and vicinity (modified

from Kimura, +32/). Legend + : central graben, , : basin occupied by Pleistocene igneous intrusions,

- : major fault and fault scarp, . : buried major fault and fault scarp, / : eastern boundary of the Ryu-

kyu Ridge, 0 : trench, 1 : active volcanoes, 2 : submarine intrusions or volcanoes since Late Pleisto-

cene time, TG : Tokara Gap, KG : Kerama Gap.

*+¼�12

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Fig. ,����������� ������ ���� +303� ����� ����� !"#$%&'(�)*+�,-� ./01 �2345624� �78�9����� :;<=>(?@*+�'ABC� 78 D< �EF� +30,� #?G;AH�I JKLM7N9O��PQRS=TC� ��R�#>AH�I 'L'J �RU VW��� R��XYZH(?@��[\��=]^'AH�I ������_= ,*5-* km�� `a�79O�T>AH�I K �� bc� 78�d��� e�fgh iR01=jd�*+'� J iR k l��m(-?@�nop=qr'AH�I 1s'(qrt�8uv� �wx��*+'AH�I �����y��� �LMz{|}~�� ��|}~�� ���|}~�� J � �r|}~��=]^'ABC� �iR �v���y�*+'AH�I J;��������� ��#'A����iR�����#���I�� � +*���������yx |}~�� ���i���i���'ABC� ����d�j�i�� �=�o¡;AH�I

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Fig. , Geologic sketch map of southern Kyushu indicating the distribution of Kagoshima Graben

(modified from Tsuyuki, +303). B : Basement sedimentary complexes of the Shimanto Terrane

and the Chichibu Terrane of Triassic to Tertiary ages, G : Tertiary granitic rocks, V : volcanic

rocks, Kr : Kirishima volcano, S : Sakurajima volcano, Km : Kaimondake volcano,

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�������� �� �� +32/�� ���������������� !"�#$%�&'()*�+,- �./�"0� +321�� ���*� $%# +/ Ma12� !"�34�567��8������9:;<+� =,>�?@A� !"B�CD#�EFG +. Ka �H/� +312� ��� ��� !"�IJCD�KLM�N� �+-.0 Ma : OP�Q/� +300��R/�ST �+33-� #� UVWXY# +* MaZ[�IJ<+#�* �\]� +33+�� ��^ 0 Ma_^�`abcd(efg$�� -*hKi$%�jk,lm(n���9op�� Fig. -#UVWXYIJCD9� �+�qrst�l�uv�F-� ��� Kodama et al. �+33/� #� $%wm�n�fxu , Ma12�yz��� ��^�{|u}p� Kamata and Kodama �+333� #UVWXY~���ju 0 Ma�, Ma, UVWXY����j9`ab�$%wmuqr�Y�����n�u , Ma12���9��� i���(z�-�u������#,-(� `ab������m�s@IJ��sIn�uo��9� R/�ST �+33-� ��CD��(���ur7����k�r�� ���*���#� � ,¡l�n�CD��¢-F#R/�ST�+33-� u£o����UVWXY�IJ9KLMfx�� `ab¤¥�#¦§¨,s©lm(�Z�� 7�Mf����m��nª��� «� 0 Ma12�s©lm �$%wmu¬­� �#� `abs§�®��¯°�

Fig. - Distribution of crustal extension of Okinawa Trough and associated

paleomagnetism (after Kamata and Kodama, +33-). Open arrow with PHS

shows the present subduction direction of the Philippine Sea plate.

±²³´14

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-, �� ���� ���� ��������������������� � !���"#�$%&"#'(�)*� �+331a��� !�����$ ������+ : Arita, +3/.� �,-./0 �Fig. ,12� 3 �$ �4�56789��:;<=�>?@AB�C"#/0DE4�E �$%C/F�)*� �+331a��GHIJKHLM�NC�#/0%� OPQR�:;S�@AST�UAVW#'(� �$ XY��Z[\.�]^.6C/U9�_`S abcd�[e0fg.� hi jklmnHoMJ pHq�rs� lmpHq�jktu��#�hvw<xwy�z{|}VW#/0jk ~�$%�/��.��_`S����0��lm���#'(� _`S ��%�0���� /,*��� +*2����.�" ��������� pHq%�0�����Z�� +����

Fig. .�� �����.��VW .,�� nHoMJpHq�����  ab+�¡/¢ .�0 ��jknHoMJ��.�£��¤¥H.6C/F� ¦�§\ pHq¢{¨�

Fig. . Contour line map of the basement rocks in southern Kyushu based on drilling data for

hot springs. Figures in parentheses from Kubota (+320) and Agency for Natural Resources

and Energy (+322). H : Hokusatu Triangular Graben, K : Kagoshima Graben.

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������� ��� +� �������������� ���������������� ,� �� �!� "��!�#��� $��� ���%�&'� (�)*+,-��./0�1'� 23�4�5�6-�78�9:;���������� �<�!��=���>?@5�A;�BC�D��E� �FG����HIJ�4��� K!�L�&�MINOP��Q20* mR���SHIJ�T���<�!�78�U�V�� WIXPYIZO��4[� Fig. /�\;&S�]I^_`O����! ab��� ,**0� ��cdeT�� f]I^_`Og ���� �� !�h"ijk\;� �l#�V��� �<�!���[m0�!�h"ijk\;�!�9:�� G�no%p��q:;�Dr�stF%�uv�! a$w5� ,***� �x%my��E� z^HY-�78�9:;����{@�T|S� }&5 a+331a� �WIXPYIZO���~��� �'��%�9:�4��E�T��� �F� (����%��)��*�[����V1'� b�� a+320� ��+��&S��%�9:k�%���kd4�� ,-���F���.-�/A�e9:;��T|S�� ����V�@4'���keU0�1�T����{@�T�� �y�d�<�!� ���6���24��345k\m4��� ��78���-����4;���T|S� ��45k&'���'�;��E� 67�����!k�<���6���;�� Fig. 0��y5�6-78��8� aA� �� ���6� ��9 aB :  ¡� +32,� �T�� Fig. 0 aA� ����<���6� ���6�¢:£¤� G� ���6��z^HY1&¥z^HY-78� (k\�� Fig. 0 aB� ��� ���6��¦��§@�V¨;-��./0©-<k\�V����<���6���ª���9:�4��� =«;� ���6��:eª>34��78��6�T'� ���k�¬��b?1�@5­®1��G���V��� �@�­®1���¯@4��ª>�AE5y4��E� ­®1�°�� ���6�±GyV�4�&S�T�� ��d² ���6kB³��C� a+303� �e� ­®1�k±E���@�U�V�´µ�V�4��G�¶�5 a+32.� e�{�·¸�V��4��� 7D aFig. /� k¹�@º'� ���6k�b

Fig. / Distribution of the Kagoshima graben, caldera structure, and Curie point

depths in southern Kyushu (modified from Kubota, ,**0). + : active volcano,

, : graben, - : fault, . : caldera and estimated caldera, / : Cretaceous to Ter-

tiary basement rocks, 0 : Curie point depth (contour interval is + km).

BC»¼16

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��������� � � �,**0� ������������ ��� �� �+331a� !� "#$�%!&$'()*�+,-�./��01� 23��456�!78�/� 9 4��! Koto �+3+0� p. +2� 4:;�<��=4>?�23��@"#$�%�AB�CD�EFG!/� �H�23��IJK-LM���� �N4OPQR�>S�T�EUVWX�./Y� 23��Z423P[4\]^H

Fig. 0 Distribution of graben in southern Kyushu (A) and the E-W cross section of the Kagoshima

Graben (B : Hayasaka, +32,). HT : Hokusatsu Triangular Graben, KG : Kagoshima Graben, Kt :

Kakuto caldera, Ar : Aira caldera, At : Ata caldera..

_`a4�b��bWX�cde /1f �,**1� 17

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�� ,.1 Ma� ,.0 Ma ����� +333� �� ������ ���������� - Ma��������� !"#�$�� %&'�()*+,�� - Ma �-.� �/01�� 23��)*+,456�7$�8� 23���9�:;<=7>?�@A� �(B��CDE���FGH�(�%&'�()*IJ�K���� L����MDNO� ����D�� PQ6�R�$�S4��D��� TU;V�SDWX���� 7�D�S�/01��� �S� + MaYZ�� [\[]^_��%&'�(�`01��a���7$�b�

.� ������Fig. 1cde Table +�� fgh�ij��iklmnop� qDrs�%&'tu�i7$��� '��icdevw +**�Vxy�� z�k�K���m{�|}�D� ~� ����{�p����~ �fgh���?��� ���YZ�)*1� ���7$�����k�S�D�� �����1�����������cW� ���������d���1����� ���f����� ���������v�;���7$�G�y�� ¡¢£¤¥¦�������B�� %&'�§�� ¨'S�©ª�S«��¬�4�����k��­®56���¯ �°±²k��³²k�� ��p��� ����´µ�¶��·¸� 47$��

Fig. 1 Geologic map of southern Kyushu (modified from Yamamoto et al., ,**-).

¹º»¼18

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.�+ ��������� ���������� ����������� � Fig. 2 �������

������� ���� ,**. �! � �����" �#$���#%� �&'(����� ������� )�*'+����� ������� �,�-. � /�)0���12���1��� �� �30456�� � 78�9���� �:;�<!=%>�)0����?@����A12BC���DE0�� �A�12��F�&�� GH&�� ���I&�� ��&�)� 0� ��BJ30��)56�� � KL��MN����� O!������! ��������� PQ�R"�STUVWX��?@#Y� Z��54� [�����@ -* km BJ����.=#\5��]� �I<2� +32. � ^$%X)0=���_��`�� &$0=a��b@!=1c��d%�e'�fg0=#\5��_(]0�� � �h)*`@��d%�bi� ]��� +. Ma +j�A���/k�l=%�h��,-mnm@op-.==�� �h(�q+�@rs.5s`/t� #\�56==�1c0.5������u�� 0�� u0v�! @� wx�� y1�2�� z{|}5J36�� �

/��4$~��4����%� ���c��! � ���cu�� 0�� u0v@���! @� y1��z{|}c�54� ��)0=�)56�� ��:DEX�� 56�7Wc��E@%� �N���89��� ::;��A<� 9�=>���?��@�! � �7WA��! N,��� +�*��z{|}�#$z{|})v5��`����} ��+2� ,**1 125%� 9�=�<���AB�� ���� ��A�� �C�� ��5J125 9�=#�� � ¡2� +31. @l�1���0�� � �=¢���£L�)¤¥�c���@D¦0�� �§�2� +30. @� ^.2#���@J���EF-. 1� ¨©�GH�! ������ªI0=«���)0��� ¬­���®¯J�� °±¯J�� MN�¯J��� K

Table + Summary of the geology of southern Kyushu.

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���������� ������������������ � !�"��#$%&'#(�) +. Ma *+,- +312. �/01 2�- �����304� +, Ma566#��789:; *Shibata and Nozawa, +302.� <2=>���?"�@ABCDEFGH�I�J�;�*=>,�"K- +31,.� L�@ABCDEFGH�MABNOFN�P41 *Yagi et al., +31/.-78��4QR66S� +2 Ma *�TU- +331. VW��304�XY�Z[�\]�^_0`a9bc- de�fgADhgi5�j���� �klm"�no��4� /* Manp�S�78 *S$%&. 9:; *qr�s,- +300 ; Shibata and Nozawa, +300.�

Fig. 2 Generalized geologic map of the Shimanto Terrane in southern Kyushu (modified

from Teraoka, ,**.). F is an estimated left-lateral fault.

tuvw20

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.�, ��������������� ����������������� ��� ������������� !��"�#$�%&�� '� (,**+) �*��� +,-���./ 2 Ma�0�123� 1 Ma

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Ma4+.3 Ma�{<�|#5!@�� }~�0� ����� ���g��� ('�� ,**+) �K !@�� ���g��� ������A? � ��w�������� !@���uv%&�� �������A��� � ������w��?��y������5##�6$ �?@� OPQRG�UV���� . Ma4, Ma�XYA� !:3� ���%���w?��./��{A�� !@� (Z[�� ,***)� ����K�A������ . Ma4, Ma�0 ��./����.�?;<%&5#�@l��D<���� a�-��� !@�� 2#mT�.�����a�� !��#�� ��./�G���6�a��/ #*t�$�l�� j�*t?m� � �� ¡���XY6�$¢£"�# (¤`�¥¦� +321)� 6 §¨ ��nopq�r�$ - Ma©ª�����������6�� ��./��mT���nopq«@�¬25!­!@��®?�¯­%&0t���°±��y�� ²�Q%&�'"Q (:*³hiQ) ��� !@�� '"QG� ,./

Ma��´����� ,Qµ��!@� (y¶�� ,**1) �� ·� "������´�����

Fig. 3 Distribution of Late Quaternary volcanic rocks in southern Kyushu (modified from Nagao,

,**+). Solid lines indicate the depth of subducting slab. V.P. : volcanic province.

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�������������� ����� ����������� +.1 Ma �Ueno et al.,

+333� ������������� ��!" #$������%���&� �'��� �+31+� �(�)� ��!*�+�,- .������/�����0����1��2%� 3�4�5�����6��/���� �Fig. 0B7,� ,- .����!��� - Ma �8�4� +312� ����� 5��� *.2

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Ma : Kaneoka and Suzuki, +31*� >4 !���@!��%� �!&����4�A���BCD)E/�� 'F��(G��!()��* - Ma �Kaneoka et al, +32.� !++�,HD�I)>4� 3!IJ>4-.�/K���������� �>�0L!-1�M�N�O2�3%PQ� RS��T-1�� ��4�5U'� +32*� B���V�!� + Ma91) !����� , MaB67)�� ��!��)��N��� , Ma:+ MaIJ��!�1@W8�&��)<=�X�>@��&�-1��T5��91!���� O2Y!9��:�ZH!O[;\!<��]>�1=����^_��� � �0L!`�a�� � �b!c���2(d>e)!fghb!?���*./2 Ma:*.-. Ma���������i� ���4� ,***� N� +,@�A��� � �b;\�B��� jCD�E5��FG���kD�!()�lH�2(dmU������ ���� +333�&2O2!I3�RgJK��N��L���&� RgJK��>����&nopq������� ,3 ka!rHnopq!�M �(� .�������N�4�� 3!stu�v'���@!��� �wO� +302�PxysD �*.2 Ma91� ! �+Q!�67�� � �!R��� +� rHnopqzS�M� ,� T� �2(d3!zSM� -� UV� �zSM! -�M �;"4� +331a�� E���{| ��M�}!��� I!~��M��� .������M�1=�� ��& .�W�B" ������ ��X@?� �X : Y��ZU� ,**-� ������������� �^�A�~�!M�����1=T�[��\!@!�?� �)=�:, Ma)E/�� .������Rj?���� ��!�)��]�����Rj?��!�)����2 .�����fgh .����� G�+���+� ~�^�! .���� �;"4� +331b� &���� E���2_� ��!_`Ba�G=�@� I�4 .����!M ��)��Bb!D�I)�cd���

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�� �+33,� ������ �������� � 0������� +� ��� !� �"� #� $��%&�� ,� '�� !� �( +*)*+,� -.�� -� /�� !� �( +**)*+,� -.�� .� /�012!� �342-.�� /� 5 2!� �672-.�� 0� 58-9:!� �5;<=�>?�� @A?� BCD� +�E-� �� F�@AG� HI�JKL-MN>OPQRS-M,8�TU���?� .�E0� �V� F����WX��?Y� ZX[\]�^_��`a`A?��\�bc��5 2��deWX� fg@�� F��hiX?� jNklmn@�� 0� �op���

/�, qrsj��-tuv� ��� !�"� �wx^%&!�Yqry@AG� -rx^��-\zt{YfY|��?� %&}x^@� 2*~+���YTU�?� �L� -.� ��� -.� Q���Lj�Yqry@A?�%&!�Y-r������ -9���� �����?B�YA?� ��-��%&-{�zt{��[Xj�� Fig. ++�L� �/��Y�y@AG� #�[�9�?��@�2����� � ���� -9:�����>G� �t� ¡�z¢�?�

Fig. +* Distribution of natural hot springs in southern Kyushu (modified from Tsuyuki, +33,)

���-t�-tuv��£ /1¤ �,**1� 23

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� �������� +*�� ��������������� ��������������� !"�#$��% &'(�)�*+,-. �����% Fig. +,)/���0123�4�05678���� -.9:;<=6>�% ?@ /** mA0** m�)@� BC�������� �4 DEFGH�)�IJKL M0*N�LO =� PQRST��UV��% LW XYZ[�J\])���^B=6>_�� `a)b7cdef1�Lg h�ij01kl=6>�% /���m3� nopq��Jr] ������ q�;sY=6>�nopcd01l��=6>�% -.(�)� 23�4 ��d*+,tuv�7w�x�%y� z���������)� +O ��>) ,O tuv���% {|�e}~|�� ���

Fig. ++ Genetic model of hot springs at the foot of Sakurajima volcano (after Tsuyuki, +33,)

Fig. +, Flow model chart of hot springs in the southwestern area of Kirishima volcano (after Tsuyuki,

+33, and Fujita et al., ,***)

����24

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������������� ����������� � ������������ �������������� �� ��������� � !��"����#�������$%��� &'� +331(�� )*+�,���-./�0������1 ��� 2�3+�4�� + Ma ���5���67 ������ 0*8!9������� �:��;��<���� =>�?�� ����� �0�����!@ A6��9"� ���#B��CDEF �9��������D3������D$%G �� &'��D5�� (H)�EF*+, I-�� J6K+. L/- 01 2M�� A6�������(3�+���N�ONPDQ7��3��456+�� *.-/ MaR*.- Ma &789S +323 ;

TH :; +323( DU� �<�=V���� J6W>3?�@AXBPY�)CZD�EF [G5���67 �9 �HMa��>\��IJG ���]K������ )*LJ^,��_MNOP`3Q�aQ^�b REF��������� �-�*�� ST�� cdef. g,U��� hh95�*+i�� -�jk�� GF ld�V��3Q���� Wm���� ����nX�oE pq$%� ���(r�X3�CD����J6��LhY�L������9 -** mR+,*** mst5� aQ^E Z[5�����Pu\5���� Fig. +-���vw?xy�z]P�D ^�6aQ^"�&'_ &`{ (T+31+( D ��a�_��� &bT +33,(� aQ^�aP |� �0EF� }E��~cC d������ &Fig. 0B�e(� �:��fg���;��<�R� ������ � ���6���<�h����3�����Y�L��9��aQ^"�&'� a8i ���LDWm|q3Nj��� �"��

�0/* m�Q���� 6$C�Fg���k������� �:�� �R�#�DX3����� 3�)*+�,����� ��Z[l�aQ^m��CD��� n�i �o��O�56��D�3�CD��r��� "n^,��"n^������pqEFr�5�������� �s^EEFr�����D5�� f���s^E���.��D(��s^E��+���$%���� ld���� &,+�t�( �_MNPEEF��5���� ��u� �ld�s^�#B5��� C�, &O��rE�5 3�� �5<�P��v56&OD3�D )*LJ^,�������C���� &OG �� ��.�������w��x�K���� y�� �#������ ��y���������:z ������� �E� {��>5� �^O���� p@�|¡¢£} @J 6:���� +�^�~��)*+�*� � ��D¤A �� ��¥PD�3q 1*8�f�������5��� &bTF +31,(� )�+�^�<� 5�����f��� "���¦D§�56��aP¨ �1����E�5 3����D�©ª3�� "���¦�jtl«E��+� &�" +,*** m( �� ¬B��

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Fig. +- Configuration map of basement rocks underneath Kagoshima city (A : modified from

Hayasaka and Oki, +31+) and the E-W cross section of this area showing the horizon of

hot water in the deposits (B : Tsuyuki, +33,)

����26

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0� ���������������������� �������� ����� �� � +* Ma

���������������������������� !�"#$��%&�'� (����� 0 Ma���)*+���,��-./�012 -./�� . Ma3, Ma$(45�6�789:�;�+�<� =�>?��@�� �ABC�DE����D�F�$��%&����%&� + Ma�������D�� 0GHI�!-JK� /"J-./��L+�<2 ����#�����D��ABC�D�� �$%��MN� ��$-./��&�'(J�O���12=��)��<2 *�*+BP �+. Ma� �Q,��4���&R�J+�<2S�6� ����T�7S-.U2��4V/�0��112<�WXW$&R�J+�<2 =�YZ��������U2��-.2�3-.2�4;[�U\�$-./���������]JU=�$0'2

� �����^56_701+�`89:;<=��� ���]JS[�����>?�8<�� *�a@^b�^�AcBCDd� Ee�^�EfFGDd� ����^��Hg�Dd��� h����������U2(*�IJ�8<�i_7<�j<� ���kKlLM =/m=n��� ��opqrXIps�tN�uv��<�j<� 1;w�xO<��*U

��yPQR �+302� : z{ST����|}~���U�:��V�����| W��^�V��XYJ� .0� +-,/�+-.-.

Arita, T. (+3/.) : The geological structure of Kagoshima Prefecture, Kyushu district, Japan.

Sci. Rep. Kanazawa Univ., no. ,, +,�+-+.

Z[ \� ]�^�_� `a��� �b K� �.cP� def�� �gh�_� i j�� kl�� �+330� : �m���� ����n&o/� JAMSTEC0���� no. +,� ,++�,+3.

Sep�� ��qR� �.fr �,***� : s�-.�:�~���t �:����=��� ���^� /*� +�++.

�@ u �+30,� : ���k�A�v�wxyz �� {��| ���^_}�^��� no. 2�.1�0,.

~��B �+32,� : �D2�� ��������� � ��^������� �A� ����������|� �x�� U@��� J��� no. +� 10�12.

~��B� �9g� �+31+� : �����:�opqrX���4��6��^��  ����^�^ P� ��^�=�^�� no. .� +/�,3.

]��R� � ��� ¡¢ � �+31.� : ���ka?��M£2���� ��^¤�� 2*� .,3�.-*.

���k �+312� : �����o¥��2¦§�¨J�� -2 p.

©eª«��¬�� �+33-� : -.�|2���������-.�:�����h­�®­¯|t��@°��±°²� �M£2�³q´r�µ¶p���· ]¸]¹)$º'»=�� -

�| ��^¡¢� no. .+� +,3�+.2.

Kamata, H. and Kodama, K. (+333) : Volcanic history and tectonics of the Southwest Japan

Arc. The Island Arc, 2, -3-�.*-.

Kaneoka, I. and Suzuki, M. (+31*) : K-Ar and fission-track ages of some obsidians from Japan.

����������|���+ /1¼ �,**1� 27

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J. Geol. Soc. Japan, 10, -*3�-+-.

Kaneoka, I., Aramaki, S., Kobayashi, T. and Oki, K. (+32.) : Pliocene and Pleistocene volcanism

in southern Kyushu : K-Ar ages of Fumoto and Isaku pyroclastic flows and related rocks.

Bull. Volcanol. Soc. Japan, ,3, /3�0,.

�������������� �+30.� : ��� �������� �� ����� +/�-.+�-.-.

����� ���� �+300� : ������� K-Ar dating �V� ��������� ��� /0� +3+�,++.

Kimura, M. (+32/) : Back-arc rifting in the Okinawa Trough. Marine and Petroleum Geology,

,, ,,,�,.*.

Kodama, K., Tashiro, H. and Takeuchi, T. (+33/) : Quaternary counterclockwise rotation of south

Kyushu, southwest Japan. Geology, ,-, 2,-�2,0.

���� �+30/� : �� �!�"� ��#�$� �� !"� 1+� .-1�./1.

Koto, B. (+3+0) : The great eruption of Sakura-jima in +3+.. J. Coll. Sci. Imp. Univ. Tokyo, -2,

+�,-1.

#%�$& �+320� : !%&''�()�*+,-�(�)�./�#�0*+1� �2��� -0�./3�.1..

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��� 1.

�� � �+312� : ������� ����������� �������� ,3� //+�//..

Shibata, K. and Nozawa, T. (+300) : K-Ar ages of granites from Amami-oshima, Ryukyu islands,

Japan. Bull. Geol. Surv. Japan, +1, .-*�.-/.

Shibata, K. and Nozawa, T. (+302) : K-Ar ages of acid rocks of Noma-misaki and Hioki moun-

tains, Kyushu, Japan. Bull. Geol. Surv. Japan, +3, ,--�,-0.

�� �� ���� � ! � "#�� $�%� �+312� : &'�( )� *+,-�� K-Ar�.� ��/01� 2.� //+�//-.

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+�#"� "#�� �8 � �,**1� : &'�k9�$�<���`��:�$V�V�/*yz� ��/01� ++-� 3/�++,.

Ueno, M., Takeda, T., Otsuka, H. and Shimada, N. (+333) : Paleomagnetic evidence for the timing

of the gold mineralization in Kagoshima, Japan. Mineral Deposits : Process to Processing

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