Figure F1. Images of ODP core samples analyzed from the subsurface of the PACMANUS hydrothermal field. Many samples consist of compositionally distinctive domains, and separate powders were generated for geochemical, mineralogical, and isotopic analyses. Here, the hand specimen expression of particular volcanic and alteration features are documented and the location of the analyzed powders are shown. In total, 75 powders derived from 54 samples were analyzed. The data are presented in Tables T1, and T2. Scale bar = 1 cm. altn = alteration, anhy =anhydrite, chl = chlorite, ill = illite, Kfsp = K-feldspar, py = pyrite, pyro = pyrophyllite. XRF = X-ray fluorescence, ICP-MS = inductively coupled plasma–mass spectrometry. A. Sample PM01 (193-1188A-2R-1, 18 cm): fresh, glassy, vesicular dacite. Bulk rock powder: P001 (XRF, ICP-MS, F, Cl,

Figure F1. Images of ODP core samples analyzed from the subsurface of the PACMANUS hydrothermal field. Many samples consist of compositionally distinctive domains, and separate powders were generated for geochemical, mineralogical, and isotopic analyses. Here, the hand specimen expression of particular volcanic and alteration features are documented and the location of the analyzed powders are shown. In total, 75 powders derived from 54 samples were analyzed. The data are presented in Tables T1, and T2. Scale bar = 1 cm. altn = alteration, anhy =anhydrite, chl = chlorite, ill = illite, Kfsp = K-feldspar, py = pyrite, pyro = pyrophyllite. XRF = X-ray fluorescence, ICP-MS = inductively coupled plasma–mass spectrometry. A. Sample PM01 (193-1188A-2R-1, 18 cm): fresh, glassy, vesicular dacite. Bulk rock powder: P001 (XRF, ICP-MS, F, Cl,

¹⁸O_silicate, ⁸⁶Sr/⁸⁷Sr_silicate). B. Sample PM02 (193-1188A-5R-1, 37 cm): weakly altered, perlitic dacite. Bulk rock powder: P002 (XRF, ICP-MS, F, Cl,

¹⁸O_silicate, ⁸⁶Sr/⁸⁷Sr_silicate). C. Sample PM05 (193-1188A-7R-1, 114 cm): domainal altered dacite with remnant perlite. Powder of separates: P003 (XRF, ICP-MS,

¹⁸O_{anhydrite + silicate}, ⁸⁶Sr/⁸⁷Sr_{anhydrite + silicate}) and P004 (XRF, ICP-MS,

¹⁸O_{anhydrite + silicate}, ⁸⁶Sr/⁸⁷Sr_{anhydrite + silicate}). D. Sample PM06 (193-1188A-8R-1, 13 cm): domainal altered dacite with remnant perlite. Powders: P071 (bulk sample: XRF, ICP-MS, F, Cl), P005 (white domains: XRF, ICP-MS,

¹⁸O_silicate, ⁸⁶Sr/⁸⁷Sr_silicate), and P006 (black network: ICP-MS,

¹⁸O_silicate,⁸⁶Sr/⁸⁷Sr_silicate). E. Sample PM07 (193-1188A-8R-1, 66 cm): light gray-green flow-banded, brecciated dacite. Bulk rock powder: P007 (XRF, ICP-MS, F, Cl,

¹⁸O_{anhydrite + silicate}, ⁸⁶Sr/⁸⁷Sr_{anhydrite + silicate}). F. Sample PM08 (193-1188A-8R-1, 13 cm): white ?perlitic, bleached coherent dacite. Bulk rock powder: P008 (XRF, ICP-MS,

¹⁸O_{anhydrite + silicate}, ⁸⁶Sr/⁸⁷Sr_{anhydrite + silicate}). G. Sample PM10 (193-1188A-11R-1, 20 cm): coherent dacite, gray kernel, and white margin. Powders: P009 (margin: XRF, ICP-MS,

¹⁸O_{anhydrite + silicate}, ⁸⁶Sr/⁸⁷Sr_{anhydrite + silicate}) and P010 (core: XRF, ICP-MS).