Review of Methane Seepages in the Okinawa Trough: Progress and Outlook

Table 2

Results of geochemical analysis associated with gas seeps in the Okinawa Trough.

Reference	Sample no.	Longitude	Latitude	Method	R/V	Water depth (m)	Results
Li et al. [17]	Core A	126°2020.4E	27°4015.0N	Gravity core	Kexue Yihao	1105	Pore water: concentrations of CH4, SO4^2-, HS^-, TA, NH^4+, PO4^3-
	Core C	126°587.2E	28°2210.8N			520
Sun et al. [18]	GT-D1	128°0800E	30°4300N	Geological dredging	Kexue Yihao	622	MDAC: mineralogical and geochemical composition, δ^13C, δ^18O, δ^56Fe, δ^57/54Fe, AMS ^14C dating
Wang et al. [19]	Core A; Site 79	126°2020.4E	27°4015N	Gravity core	Kexue Yihao	1105	TOC, pyrites: δ^34S; Pore water: concentrations of CH4, SO4^2-
Peng et al. [20]	GT-D1	N.D.	N.D.	Geological dredging	Kexue Yihao	N.D.	MDAC: mineralogical and geochemical composition, pyrites: δ^34S, δ^56Fe
Li et al. [22]	CI, CII, CIII, CIV, CV	128°08E	30°43N	Geological dredging	Kexue Yihao	N.D.	MDAC: mineralogical and geochemical composition, δ^13C, δ^18O, functional genes
Xu et al. [23]	C01	127°1955E	28°4136N	Gravity core	Xiangyanghong Ershihao	910	Pore water: concentrations of CH4, Na^+, K^+, Cl^-, NH4+, Mg^2+, Ca^2+, SO4^2-, δ^13CDIC
	C10	127°2117E	28°3848N			960
	C25	125°4340E	26°3820N			1000
Guan et al. [24]	D2, D12, D30, GGD5, GGD16	N.D.	N.D.	Geological dredging	Kexue Yihao	540-700	MDAC: mineral composition, δ^13C, δ^18O; Biomarker: δ^13C
Wang et al. [26]	ESC-15-08	126°5034.2E	27°5627N	Gravity core	Haidahao	~1600	MDAC: mineral composition, δ^13C, δ^18O; Pore water: concentrations of SO4^2-, CH4, Ca^2+, Mg^2+, Sr^2+, Ba^2+, TA, DIC, δ^13C^DIC
Zhang et al. [49]	W26, W31, W45, W59	N.D.	N.D.	CTD	Kexue Yihao	~900	Seawater: DIC, DOC, δ^13CDIC, δ^13CDOC
Cao et al. [27]	5GD1	N.D.	N.D.	Geological dredging	Xiangyanghong Ershihao	603	MDAC: mineral composition, δ^13C, δ^18O, U-Th dating
Zhang et al. [50]	32 stations	N.D.	N.D.	CTD	Zhangjianhao	N.D.	Seawater: temperature, salinity, concentration of CH4
Li et al. [16]	D1	N.D.	N.D.	Seafloor drilling	Haidahao	965	Pore water: concentrations of SO^42-, CH4, δ^13C-CH4, δD-CH4
	D2	N.D.	N.D.			1047
	D4	N.D.	N.D.			1048
	D5	N.D.	N.D.			921
Xu et al. [28]	R3-C1	N.D.	N.D.	ROV push core	Zhangjianhao	953	Pore water: concentrations of CH4, Cl^-, Br^-, SO4^2-, Na^+, Li^+, Mg^2+, Ca^2+, Sr^2+, NH4^+, DIC, δ^13CDIC, δ^13C-CH4, δD-CH4
	R3-C2	N.D.	N.D.			957
	R4-C2	N.D.	N.D.			924
	R4-C4	N.D.	N.D.			922
	R6-C1	N.D.	N.D.			913
	R6-C4	N.D.	N.D.			915
	G08	N.D.	N.D.	Gravity core		1020
	G04	N.D.	N.D.			958

N.D.: not documented.