Table 3.

Hydrothermal Fluid Samples Main Features

									C in hydrothermal fluid (ppt)
Sample name	Site	Description	Depth (m)	T(°C)	pH	Cl-mM	Fluid %	Pre-C fold	Glu	Ala	Met	Trp	Pro	Gly	Lys	Tyr	Phe	Leu
MAD-D2-Ti2D	seawater	reference	2291	2	7.84	550	nm	30	nd	344	nd	nd	nd	nd	nd	nd	nd	x
MAD-D3-Ti3G	Rainbow	black smoker	2307	350	3.23	761	97	25	nd	nd	nd	x	nd	nd	nd	nd	nd	nd
MAD-D6-Ti3D*	Rainbow	black smoker	2265	253	4.72	638	40	50	nd	69	x	nd	nd	nd	nd	nd	x	x
MAD-D6-Ti2G	Rainbow	black smoker	2265	353	3.41	711	73	40	nd	nd	nd	nd	nd	nd	nd	nd	x	x
MAD-D8-Ti1D	Rainbow	black smoker	2305	350	3.36	703	71	25	nd	nd	nd	nd	x	nd	nd	nd	x	x
MAD-D8-Ti3D	Rainbow	diffuser	2297	52.5	6.34	560	7	40	nd	41	nd	nd	nd	nd	nd	nd	x	x
SE-D2-Ti2	Ashadze 1	black smoker	4088	353	3.95	595	76	25	nd	nd	nd	x	nd	nd	nd	nd	x	54.2
SE-D2-Ti3	Ashadze 1	black smoker	4088	353	3.89	601	81	33	nd	nd	nd	x	nd	nd	nd	nd	x	14.9
SE-D3-Ti4*	Ashadze 1	black smoker	4088	355	4.13	604	81	25	nd	nd	nd	x	nd	nd	nd	nd	x	x
SE-D4-Ti3	Ashadze 2	black smoker	>3263	—	6.17	452	36	50	nd	nd	nd	nd	nd	nd	nd	nd	x	x
SE-D6-Ti1	Logatchev 1	black smoker	3021	346	4.97	517	71	50	nd	nd	nd	nd	nd	nd	nd	nd	x	x
SE-D7-Ti1-L2	Logatchev 2	black smoker	2700	308	4.44	171	93	50	nd	nd	nd	nd	nd	nd	nd	nd	x	x

As seawater mixing occurred in some samples, the % of pure fluid is given in the Fluid column. The Pre-C column gives how much the samples were concentrated before analyses (in fold). Concentrations are given in ppt, i.e., in ng L⁻¹, and refer to the concentration in the natural hydrothermal fluid originally, before preconcentration.

^*Spiked samples with 50 μL of the 1000-fold diluted standard solution.

nd: not detected. nm: not measured.