Table 1. Composition of quartz and basalt blanks.

Gas	Qtz blank mean (mols)	Qtz blank s.d. (mols)	Basalt blank mean (mols)	Basalt blank s.d. (mols)
H2	5.1E−15	1.31E−14	3.01E−15	4.09E−15
He	Below detection	0	2.12E−16	2.50E−16
CH4	4.14E−14	2.08E−14	6.62E−16	1.42E−15
N2	2.84E−15	3.2E−14	1.14E−12	6.81E−13
O2	1.1E−15	4.7E−16	0	0
Ar	1E−16	1.6E−16	3.01E−16	5.37E−16
CO2	4.5E−15	2.83E−15	5.50E−11	4.27E−11