Thermochronology of hydrothermal alteration zones in the Kii Peninsula, southwest Japan: an attempt for detecting the thermal anomalies and implications to the regional exhumation history

Sueoka, Shigeru; Iwano, Hideki; Danhara, Tohru; Niwa, Masakazu; Kanno, Mizuho; Kohn, Barry P.; Kawamura, Makoto; Yokoyama, Tatsunori; Kagami, Saya; Ogita, Yasuhiro; Hirata, Takafumi

doi:10.1186/s40623-023-01921-5

Earth, Planets and Space

Table 4 Summary of AFT and ZFT data

From: Thermochronology of hydrothermal alteration zones in the Kii Peninsula, southwest Japan: an attempt for detecting the thermal anomalies and implications to the regional exhumation history

Sample code	Grains	Spontaneous FT		U measurement		U standard		U [ppm]	ζ value [cm²/year]	Pooled FT age ± 1σ [Ma]	Cl [wt%]
Sample code	Grains	ρ_s [10⁶ cm⁻²]	N_s	ρ_U [10⁹ cm⁻²]	N_U	ρ_U-std [10⁹ cm⁻²]	N_U-std	U [ppm]	ζ value [cm²/year]	Pooled FT age ± 1σ [Ma]	Cl [wt%]
Zircon
HJG1-F	30	4.37	970	18.30	4230785	5.279	47513	291	42.5 ± 1.2	25.7 ± 1.2	–
HJG1-0–5cm	30	7.36	1986	16.90	4554139	5.279	47513	268	42.5 ± 1.2	48.7 ± 1.9	–
HJG1-5–10cm	30	6.43	1735	22.10	5954473	4.971	44741	373	42.5 ± 1.2	30.7 ± 1.2	–
HJG1-0m	28	4.77	1164	5.59	1367571	1.333	15697	352	46.8 ± 1.0	26.5 ± 1.2	–
HJG1-1m	30	6.47	1657	6.35	1619317	1.430	16835	373	46.8 ± 1.0	34.1 ± 1.4	–
HJG1-3m	30	5.51	1389	6.08	1511646	1.359	16006	376	46.8 ± 1.0	29.2 ± 1.3	–
HJG1-10m	30	5.10	1335	6.15	1596112	1.345	15835	384	46.8 ± 1.0	26.3 ± 1.1	–
HJG1-20m	30	4.15	1192	5.13	1461429	1.356	15972	318	46.8 ± 1.0	25.8 ± 1.2	–
HJG2-F	30	7.69	2076	21.40	5766492	4.971	44741	361	42.5 ± 1.2	37.9 ± 1.5	–
HJG2-0–5cm	30	6.75	1822	20.10	5431976	4.783	43043	353	42.5 ± 1.2	34.0 ± 1.3	–
HJG2-5–10cm	30	8.97	2422	20.90	5655631	4.783	43043	368	42.5 ± 1.2	43.4 ± 1.6	–
HJG2-0m	30	4.23	1121	5.55	1440745	1.345	15842	347	46.8 ± 1.0	24.5 ± 1.1	–
HJG2-1m	30	4.20	1108	4.55	1188763	1.341	15791	285	46.8 ± 1.0	29.2 ± 1.4	–
HJG2-3m	30	3.90	1111	5.02	1367704	1.349	15883	313	46.8 ± 1.0	25.6 ± 1.2	–
HJG2-10m	30	4.52	1312	4.62	1301212	1.320	15540	294	46.8 ± 1.0	31.1 ± 1.4	–
HJG3-Upb	36	3.10	1733	23.30	12849644	5.022	45194	390	48.6 ± 2.2	16.4 ± 0.8	–
HJG4-0m	30	3.78	993	5.05	1323100	1.369	16116	310	46.8 ± 1.0	24.0 ± 1.1	–
HJG4-1m	30	4.67	1229	4.97	1307709	1.299	15299	322	46.8 ± 1.0	28.5 ± 1.3	–
HJG4-3m	30	5.60	1293	6.33	1405870	1.238	14581	429	46.8 ± 1.0	26.6 ± 1.2	–
HJG4-10m	30	5.41	1559	6.14	1743630	1.186	13967	435	46.8 ± 1.0	24.8 ± 1.0	–
Apatite
HJG1-0–5cm	29	0.228	82	3.94	1416827	1.616	14541	34	253 ± 18	11.8 ± 1.6	0.22
HJG1-5–10cm	28	0.194	70	2.49	897322	1.511	13599	23	253 ± 18	14.9 ± 2.1	0.15
HJG1-0m	36	0.182	103	0.65	370749	0.3119	3820	29	254 ± 18	11.0 ± 1.5	0.16
HJG1-1m	36	0.201	164	0.90	718624	0.3119	3820	40	254 ± 18	9.0 ± 1.0	0.24
HJG1-3m	36	0.187	161	0.74	640728	0.3119	3820	33	254 ± 18	9.9 ± 1.1	0.15
HJG1-10m	30	0.174	129	0.66	481343	0.3225	3951	29	254 ± 18	11.0 ± 1.3	0.14
HJG1-20m	30	0.274	194	0.12	824188	0.3225	3951	52	254 ± 18	9.6 ± 1.0	0.29
HJG2-F2	30	0.244	88	2.32	834729	0.9654	8688	34	253 ± 18	12.9 ± 1.7	0.11
HJG2-0–5cm	30	0.253	91	2.03	732329	0.6609	5948	43	253 ± 18	10.4 ± 1.4	0.21
HJG2-5–10cm	30	0.208	75	0.65	234188	0.3685	3317	25	253 ± 18	14.9 ± 2.2	0.57
HJG2-0m	30	0.359	255	0.12	868650	0.3225	3951	51	254 ± 18	12.0 ± 1.2	0.31
HJG2-1m	30	0.246	170	0.94	639748	0.3169	3883	41	254 ± 18	10.7 ± 1.2	0.36
HJG2-3m	30	0.203	132	0.70	430783	0.3169	3883	31	254 ± 18	12.3 ± 1.5	0.64
HJG2-10m	30	0.187	125	0.82	517618	0.3169	3883	36	254 ± 18	9.7 ± 1.2	0.33
HJG3-Upb	30	0.0187	14	0.23	174686	1.674	20512	2	262 ± 24	17.5 ± 5.1	0.004
HJG4-0m	18	0.272	68	0.10	283953	0.3104	3803	46	254 ± 18	9.4 ± 1.4	0.14
HJG4-1m	30	0.123	82	0.44	272067	0.3104	3803	20	254 ± 18	11.9 ± 1.7	0.14
HJG4-3m	30	0.202	134	0.79	514705	0.3104	3803	36	254 ± 18	10.2 ± 1.2	0.71
HJG4-10m	30	0.242	177	0.88	605794	0.3104	3803	40	254 ± 18	11.5 ± 1.3	0.23

The apatite chlorine content is correlated with the AFT annealing rate (e.g., Carlson et al. 1999). The pooled fission-track ages (t) and their errors (σ) were calculated using the following equations:
\(t=\frac{1}{{\lambda }_{D}}ln\left(1+{\lambda }_{D}\bullet g\bullet \zeta \frac{\sum {N}_{s}}{\sum {N}_{U}}{\rho }_{U-std}\right)\)
\(\sigma =t\sqrt{\frac{1}{\sum {N}_{s}}+\frac{1}{\sum {N}_{U}}+\frac{1}{\sum {N}_{U-std}}+{\left(\frac{{\sigma }_{\zeta }}{\zeta }\right)}^{2}}\)
where λ_D is total decay constant of ²³⁸U (= 1.55125 × 10⁻¹⁰ year⁻¹), and g is geometry factor (= 0.5 for internal surfaces). Nancy 91500 zircon and Durango apatite were used as uranium standards (Additional file 1: Text S2). [Cl, chlorine content; N_s, number of spontaneous tracks; N_U, number of uranium measurements on unknowns; N_U-std, number of uranium measurements on standard; ρ_s, density of spontaneous tracks; ρ_U, density of uranium measurements on unknowns; ρ_U-std, density of uranium measurements on standard; U, uranium content; ζ, zeta calibration factor; σ_ζ, error of zeta calibration factor]

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