09-.n R38-V412

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1 No.38 (23) pp Whole - Rock Chemistry for Eruptive Products of Fuji Volcano, Central Japan: Summary of Aanalytical Data of 847 Samples. Masaki TAKAHASHI 1, Masanaga KOMINAMI 2, Yasuhiko NEMOTO 2, Yukie HASEGAWA 3, Tadashi NAGAI 4, Hidemasa TANAKA 3, Naoto NISHI 2 and Maya YASUI 1 (Received September 3, 22) The whole-rock chemistry for eruptive products of Fuji volcano is studied based on 847 newly obtained analytical data. The volcanic activity of Fuji volcano consists of 6 stages which are proposed on the basis of tephrochronology and whole-rock chemistry of eruptive products; they are the stage-1 (1 to 66ka), stage-2 (66 to 5 ka), stage-3 (5 to 25 ka), stage-4 (25 to18 ka), stage-5 (18 to 13 ka), stage-6 (13 to 4.5 ka), stage-7 (4.5 to 3. ka), stage-8 (3. to 2. ka) and stage-9 (2.ka to Recent). The eruptive products of stage-1 to stage-5 are members of the Ko - Fuji volcano and those of the stage-6 to stage-9 belong to the Shin - Fuji volcano. The whole - rock chemistry of eruptive products were abruptly changed at about 18 ka; the magmas erupted before 18 ka are called here the Ko - Fuji magmatic group and those after 18 ka the Shin - Fuji magmatic group. The Shin - Fuji magmatic group is enriched in incompatible components such as TiO 2, K 2 O, P 2 O 5, Rb, Ba, Zr and Nb, and shows higher ratios of Rb/Y, Ba/Y, Zr/Y and Nb/Y compared with the Ko -Fuji magmatic group. The difference of both magmatic group cannot be explained by a simple crystallization differentiation of the same parental magma, but it was produced by the melting of chemically heterogeneous source mantle. Keywords: Fuji volcano, magma, whole - rock chemistry, incompatible element, differentiation, melting, heterogeneous mantle km Tsukui Miyaji et al Arculus et al Togashi and Terashima Department of Geosystem Sciences, College of Humanities and Sciences, Nihon University: , Sakurajosui, Setagaya-ku Tokyo Japan. 2 Master course, Graduate School of Sciences and Technology, and Graduate School of Sciences, Ibaraki University: 2 1 1, Bunkyo Mito Japan 3 Department of Earth Sciences, Ibaraki University: 2 1 1, Bunkyo Mito Japan 4 Master course, Graduate School of Integrated Basic Sciences, Nihon University: , Sakurajosui, Setagayaku Tokyo Japan

2 ka 1 ka Pm 1 1 I II 8 1ka I 1ka II II I II 5ka Pm 1 1ka 1ka ka OP 66 ka 1 ka X XRF 123 Rb Sr Ba Zr Y Ni Cr V Zn Cu 1 Nb 2 1 X 38E3.4 g 1 1 Li 2 B 4 O 7 LiBr aq. 4g 7g

3 kv 5 ma Rh X SiO 2.5 wt TiO 2.2 wt Al 2 O 3.3 wt FeO.6 wt MnO.4 wt MgO.5 wt CaO.4 wt Na 2 O.7wt K 2 O.2 wt P 2 O 5.4 wt Rb 3.46 ppm Sr 11.8 ppm Ba 23.4 ppm Y 1.77ppm Zr 9.68 ppm Cr 1.4 ppm Ni 1.69 ppm V 8.92 ppm Zn 4. ppm Cu 2. ppm FeO.9Fe 2 O X g Li 2 B 4 O LiBr g 2 Li 2 B 4 O 7 LiBO : g 5 kv 5 ma Rh X SiO 2.49 wt TiO 2.15 wt Al 2 O 3.15wt FeO.4 wt MnO.2 wt MgO.17 wt CaO.6wt Na 2 O.39 wt K 2 O.6 wt P 2 O 5.2 wt Nb.24 ppm 3 X PW g Li 2 B 4 O 7 1:5 1 5 kv 5 ma Rh X SiO 2.14 wt TiO 2.11wt Al 2 O 3.67 wt FeO.77wt MnO.4 wt MgO.94wt CaO.56 wt Na 2 O.31 wt K 2 O.24wt P 2 O 5.3wt 4. K 2 O P 2 O 5 9 stage kastage ka I III stage ka IV VII stage ka VII stage ka VIII stage ka stage ka stage-8 3 2ka stage-9 2ka

4 Fig.1 K 2 O vs. SiO 2 and P 2 O 5 vs. SiO 2 diagrams for whole-rock chemistry of Ko-Fuji air-fall scoria in the outcrop of Kami shibanda, along with that of Akaiwa and Yoshidaguchi trail. 1: scoria in the lower horizon of AT; 2: scoria in the upper horizon of AT; 3: scoria in the upper horizon of Y13; 4: clasts in Y13 mud-flow deposit.; 5: essential clasts of pyroclastic fall deposit at Akaiwa; 6: Ko-Fuji lavas in the Yoshidaguchi Yamazaki 1992 Mf I Mf IV 5 Mf I TP 5kaTP Mf I Mf I Mf I Mf II TP AT 25ka Mf III AT Mf IV 66 12

5 Mf II Mf III Mf I 5m 3 1 cm 2 Mf I 1 m 5 3 cm 2 Mf II 5m 1m 2m 3 flow unit 5 1 cm 1.5 m Mf III 1 m 1 5 cm 1 m 1m 1 m 1992 Y13 18 ka 1992 OP AT 4 ka Y98 13 ka Y14 stage-4 stage-5 Y13 K 2 O P 2 O 5 Fig.1 Y13 K 2 O P 2 O 5 Y13 stage-4 stage- 5 Y13 Y13 4 ka 13ka Fig.2 5. SiO 2 FeO /MgO stage clast by clast grain by grain composite clast grain clast by clast

6 (m) 3 Y13 FeO*/MgO SiO2(wt%) stage-5 18ka K2O(wt%) P2O5(wt%) (m) 3 Y13 25 stage AT 25ka 2 AT 15 stage FeO*/MgO SiO2(wt%) K2O(wt%) P2O5(wt%) Fig.2 Columnar section of the outcrop of Ko-Fuji pyroclastic fall deposit at Kamishibanda. Each sample is collected from one fall unit. Vertical scale is the thickness of pyroclastic fall deposit. composite grain 5. 1 stage-1 stage-5 stage-1 stage-5 Fig.3 Fig.4 SiO 2 stage-1 SiO 2 stage-4 TiO 2 SiO 2 stage-1 stage-3 stage-4 stage-5 Al 2 O 3 SiO 2 stage-1 stage-5 FeO SiO 2 stage-5 K 2 O P 2 O 5 stage-1 stage-3 stage-4 stage-5 MnO MgO CaO SiO 2 Na 2 O FeO /MgO stage-2 stage-3 FeO /MgO stage-4 stage-5 stage-1 TiO 2 stage-1 stage- 2 stage-3 stage-4 stage-5 stage-1 FeO /MgO TiO 2 stage-1 FeO /MgO TiO

7 Al 2 O 3 FeO /MgO stage-1 stage-5 FeO MnO stage- 1 FeO /MgO stage-1 FeO /MgO MgO FeO /MgO stage-1 CaO FeO /MgO Na 2 O FeO /MgO stage-4 K 2 O P 2 O 5 FeO / MgO stage-5 stage-5 TiO 2 K 2 O P 2 O 5 stage-6 stage-9 stage-3 stage-5 Fig. 2 FeO /MgO stage-3 stage-4 stage-5 SiO 2 stage-3 stage-4 stage-5 K 2 O P 2 O 5 stage-5 Y stage-6 stage-9 stage-6 stage-9 Fig.5 6 SiO 2 Fig.5 stage-6 TiO 2 Al 2 O 3 MnO CaO SiO 2 MgO Na 2 O K 2 O P 2 O 5 SiO 2 MgO stage-6 Na 2 O K 2 O P 2 O 5 stage-6 FeO /MgO Fig.6 stage-6 stage- 7 FeO /MgO 2.5 TiO 2 FeO K 2 O P 2 O 5 FeO / MgO TiO 2 K 2 O P 2 O 5 stage-6 stage-7 MgO CaO FeO /MgO MgO stage-7 Al 2 O 3 MnO Na 2 O FeO /MgO MnO stage SiO 2 FeO / MgO SiO 2 FeO /MgO Fig.7 SiO 2 stage wt stage-2 stage-3 FeO /MgO stage-1 stage-2 stage-3 stage-4 stage-5 stage stage-7 stage-8 stage-9 6. stage-1 stage-5 Fig.8 Fig.9 Fig.9 Stage-9 SiO 2 FeO /MgO Rb Ba Nb Zr Y stage-1 stage-2 stage-3 stage-4 stage-5 stage-9 Cr Ni V stage-5 stage-9cu Zn stage-1-2 stage-3 stage-4-5 Cu Zn V stage-1-2 SiO Rb Ba Zr

8 Fig.3 SiO 2 variation diagrams of whole-rock major element chemistry for the eruptive products of Ko-Fuji volcano. 1 : stage- 1 (pyroclastic fall deposit); 2 : stage-2 (clasts of Ko-Fuji mud-flow deposit); 3 : stage-3 (pyroclastic fall deposit); 4 : stage-3 (clasts of Ko-Fuji mud-flow deposit); 5 : stage-4 (pyroclastic fall deposit); 6 : stage-4 (clasts of Ko-Fuji mudflow deposit); 7 : stage-5 (pyroclastic fall deposit and lava); 8 : stage-5 (clasts of Ko-Fuji mud-flow deposit) 7 124

9 (wt%) (wt%) 15 CaO 1 K2O Na2O.4 P2O SiO2 (wt%) SiO2 (wt%) Fig

10 (wt%) (wt%) 54 SiO2 15 FeO* 52 CA 1 5 TH TiO2.3 MnO Al2O3 8 MgO FeO*/MgO FeO*/MgO Fig.4 FeO /MgO diagrams of whole-rock major element chemistry for the eruptive products of Ko-Fuji volcano. Symbols are the same as in Fig.3. CA: calcalkaline rock-series ; TH: tholeiitic rock-series

11 Fig

12 Fig.5 SiO 2 variation diagrams of whole-rock major element chemistry for the eruptive products of Shin-Fuji volcano. 1: stage-6 (lava); 2: stage-7 (lava); 3: stage-8 (lava); 4: stage-9 (lava)

13 (wt%) (wt%) Na2O K2O CaO.5 P2O SiO2 (wt%) SiO2 (wt%) Fig

14 Fig.6 FeO /MgO diagrams of whole-rock major element chemistry for the eruptive products of Shin-Fuji volcano. Symbols are the same as in Fig.5. CA: calcalkaline rock-series ; TH: tholeiitic rock-series 76 13

15 Fig

16 N N 2 1 Stage-9 (2ka ) Stage-8 (3 2ka) Stage-7 (4.5 3ka) Stage-6 (13 4.5) Stage-5 (18 13ka) Stage-4 (25 18ka) Stage-3 (5 25ka) Stage-2 (66 5ka) Stage-1 (1 66ka) SiO2 (wt%) FeO*/MgO Fig.7 Histograms of whole-rock SiO 2 content and FeO /MgO ratio for the eruptive products of each stage of Fuji volcano

17 Nb Y Fig.1 Rb/Y Zr/Y stage- 1 stage- 2 stage-3 stage-4 stage-5 stage-9 Ba/Y Nb/Y stage-5 Rb/Zr Ba/Zr Rb/Ba Rb/Nb Ba/Nb Zr/Nb 8. 18ka 18ka SiO 2 TiO 2 FeO MnO Na 2 O K 2 O P 2 O 5 FeO /MgO Fig.11 Al 2 O 3 MgO CaO Rb Ba Nb Zr Y V Zn Cu Sr Ni Cr Fig.12 FeO /MgO TiO 2 K 2 O P 2 O 5 Al 2 O 3 FeO MnO MgO CaO Na 2 O Fig.13 Rb Ba Nb Zr Ni Cr Sr Y V Zn Cu Fig.14 Rb/Y Ba/Y Zr/Y Nb/Y Rb/Ba Rb/Zr Rb/Nb Ba/Zr Ba/Nb Zr/Nb Fig SiO 2 FeO /MgO TiO 2 K 2 O P 2 O 5 Rb Ba Nb Zr Sr Rb/Ba Rb/Zr Ba/Zr Rb/Nb Ba/Nb Zr/Nb TiO 2 K 2 O P 2 O 5 Rb Ba Nb Zr Rb/Y Ba/Y Zr/Y : stage-1 stage-9 9 stage ka stage ka stage ka stage ka stage ka stage ka stage ka stage ka stage-9 2.ka stage-1 stage-5 stage-6 stage ka 18ka 3 66ka stage-1 SiO 2 4 TiO 2 K 2 O P 2 O 5 Rb Ba Nb Zr

18 Fig.8 SiO 2 variation diagrams of whole-rock trace element chemistry for the eruptive products of Ko-Fuji volcano. Symbols are the same as in Fig

19 Fig

20 Fig.9 FeO /MgO diagrams of whole-rock trace element chemistry for the eruptive products of Ko-Fuji volcano. Symbols are the same as in Fig.3 excluding 9. 9 indicates composition of trace elements for Shin-Fuji volcano

21 Fig

22 Fig.1 Ratio of incompatible elements for the eruptive products of Ko-Fuji volcano. Those of Shin-Fuji volcano (stage-9) are also shown as a reference. Symbols are the same as in Fig

23 Fig

24 Fig.11 SiO 2 variation diagrams of major element chemistry for the Ko-Fuji and Shin-Fuji magmatic group. 1: Ko-Fuji; 2: Shin- Fuji

25 Fig.12 FeO /MgO diagrams of major element chemistry for the Ko-Fuji and Shin-Fuji magmatic group. Symbols are the same as in Fig

26 Fig.13 SiO 2 variation diagrams of trace element chemistry for the Ko-Fuji and Shin-Fuji magmatic group. Symbols are the same as in Fig

27 Fig.14 FeO /MgO diagrams of trace element chemistry for the Ko-Fuji and Shin-Fuji magmatic group. Symbols are the same as in Fig

28 Fig.15 Ratio of incompatible elements for the Ko-Fuji and Shin-Fuji magmatic group. Symbols are the same as in Fig

29 Rb/Y Ba/Y Zr/Y 5 2 X Arculus, R. J., Gust, D. A. and Kushiro, I. (1991) : Fuji and Hakone. National Geographic Research & Exploration, 7, Tephrochronology Miyaji, N., Endo, K., Togashi, S. and Uesugi, Y. (1992) : Tephrochronological history of Mt.Fuji. in Volcanoes and Geothermal Fields of Japan (ed. Kato, H. and Noro, H.) 29th IGC Field Trip Guide Book, 4, / Togashi, S. and Terashima, S. (1997) : The behavior of gold in unaltered island arc tholeiitic rocks from Izu-Oshima, Fuji, Osoreyama volcanic areas, Japan. Geochim. Cosmochim. Acta, 61, Tsukui, M. (1987 MS.) : A magma reservoir and its evolution beneath a polygenetic volcano. Doctoral Thesis Univ. Tokyo, p pp Yamazaki, H. (1992) : Tectonics of a plate collision along the northern margin of Izu Peninsula, central Japan. Bull. Geol. Surv. Japan, 43,

30 Table 1 Major element chemistry for the eruptive products of Fuji volcano. Top numeral of each sample number represents stage of volcanic activity. sample number of bold type: analyzed in Ibaraki University (XRF, Rigaku 327); sample number of normal type: analyzed in Earthquake Research Institute, Univ. Tokyo (XRF, Rigaku 38E3); sample number of normal type with under line: analyzed in Earthquake Research Institute, Univ. Tokyo (XRF, PhillipsPW24). SI: samples from Kamishibanda (SI 1 to 59: stage-3; SI62 to 95: stage-4; SI98 to 1-2: stage-5)

31 Table

32 Table

33 Table

34 Table

35 Table

36 Table 2 Trace element chemistry for the eruptive products of Fuji volcano. All samples are analyzed in Earthquake Research Institute Univ. Tokyo (XRF, Rigaku 38E3) except for Nb which is analyzed in Ibaraki University (XRF, Rigaku 327). (ppm) Rb Sr Ba Y Zr V Cr Ni Cu Zn Nb (ppm) Rb Sr Ba Y Zr V Cr Ni Cu Zn Nb SI SI SI SI SI SI Si S S S S S SI S SI S SI SI SI SI SI SI SI SI SI SI SI SI SI SI SI SI

37 Table 2-2 (ppm) Rb Sr Ba Y Zr V Cr Ni Cu Zn Nb (ppm) Rb Sr Ba Y Zr V Cr Ni Cu Zn Nb

38 Appendix : Maps showing the sampling localities of analyzed samples 1:25, 1:25, 5m :25, 5m :25, 5m :25, 5m

39 1:25, 5m

40 1:25, 5m :25, 5m

41 :25, 5m

42 1:25, 5m :25, 5m

43 1:25, 5m

44 1:25, 5m :25, 5m

45 1:25, 5m :25, 5m :25, 5m :25, 5m

46 :25, 5m

47 :25, 5m

48 11 164

49 1:1, m 2 4 1:1, m

50 1:1, m 2 4 1:1, m

N Fig.1 Map showing the location of Komochi volcano (open star). The contours show the depth of upper surface of subducting Pacific plate (grey lines)

N Fig.1 Map showing the location of Komochi volcano (open star). The contours show the depth of upper surface of subducting Pacific plate (grey lines) No.53 2018 pp.77 96 102 Whole-rock Chemistry for Radial Dike Rocks in the Komochi Volcano, Central Japan: Summary of Analytical Data of 102 Dikes Masaki TAKAHASHI, Seiji KUBO, Naoaki TAKASUGI, Tamotsu