Table 1. EM compositions of hydrothermal fluids.

	João			Menorah			Camel			Sleepy
	2008	2009	2010	2008	2009	2010	2008	2009	2010	2009
pH	5.52	6.06	5.60	5.52	5.66	5.57	5.50	5.77	5.62	5.90
EM NH4+ (mmol kg−1)	—	5.17	5.63	—	4.77	4.68	—	5.77	6.13	4.52
EM H2S (mmol kg−1)	4.71	3.35	4.60	4.60	2.62	3.28	4.48	3.17	4.32	3.24
EM Na (mmol kg−1)	383	395	391	388	404	296	386	392	395	404
EM K (mmol kg−1)	34.9	34.8	33.0	34.8	36.8	24.9	35.1	34.4	32.1	36.3
EM Ca (mmol kg−1)	25.9	48.7	26.7	26.0	29.4	20.2	25.6	30.6	26.3	27.7
EM Si (mmol kg−1)	14.63	15.11	14.63	14.95	15.85	11.29	14.91	15.57	14.27	16.25
EM Cl (mmol kg−1)	502	477	519	500	475	350	496	478	589	475
EM CO2 (mmol kg−1)	22.28	26.01	—	25.15	25.08	—	21.52	25.41	—	25.82
EM H2 (mmol kg−1)	4.76	4.81	—	4.99	4.69	—	4.90	4.82	—	5.50
EM CH4 (mmol kg−1)	13.68	12.60	—	13.30	12.52	—	15.12	13.45	—	15.55

Hydrothermal fluids collected from four different chimneys in 2008, 2009 and 2010. The chimneys were João, Menorah, Camel and Sleepy. EM hydrothermal fluid compositions have been calculated assuming no Mg in the hydrothermal fluids and 52 mmol per kg Mg in the seawater.