@article {ISI:000345545100011,
	title = {{The Anatomy of a Buried Submarine Hydrothermal System, Clark Volcano, Kermadec Arc, New Zealand}},
	journal = {ECONOMIC GEOLOGY},
	volume = {109},
	number = {8},
	year = {2014},
	month = {dec},
	pages = {2261{\textendash}2292},
	type = {Article},
	abstract = {Clark volcano of the Kermadec arc, northeast of New Zealand, is a large stratovolcano comprised of two coalescing volcanic cones; an apparently younger, more coherent, twin-peaked edifice to the northwest and a relatively older, more degraded and tectonized cone to the southeast. High-resolution water column surveys show an active hydrothermal system at the summit of the NW cone largely along a ridge spur connecting the two peaks, with activity also noted at the head of scarps related to sector collapse. Clark is the only known cone volcano along the Kermadec arc to host sulfide mineralization. Volcano-scale gravity and magnetic surveys over Clark show that it is highly magnetized, and that a strong gravity gradient exists between the two edifices. Modeling suggests that a crustal-scale fault lies between these two edifices, with thinner crust beneath the NW cone. Locations of regional earthquake epicenters show a southwest-northeast trend bisecting the two Clark cones, striking northeastward into Tangaroa volcano. Detailed mapping of magnetics above the NW cone summit shows a highly magnetized ring structure 350 m below the summit that is not apparent in the bathymetry; we believe this structure represents the top of a caldera. Oblate zones of low (weak) magnetization caused by hydrothermal fluid upflow, here termed burn holes, form a pattern in the regional magnetization resembling Swiss cheese. Presumably older burn holes occupy the inner margin of the ring structure and show no signs of hydrothermal activity, while younger burn holes are coincident with active venting on the summit. A combination of mineralogy, geochemistry, and seafloor mapping of the NW cone shows that hydrothermal activity today is largely manifest by widespread diffuse venting, with temperatures ranging between 56 degrees and 106 degrees C. Numerous, small ({\textless}= 30 cm high) chimneys populate the summit area, with one site host to the similar to 7-m-tall {\textquoteleft}{\textquoteleft}Twin Towers{\{}{\textquoteright}{\textquoteright}{\}} chimneys with maximum vent fluid temperatures of 221 degrees C (pH 4.9), consistent with delta S-34(anhydrite-pyrite) values indicating formation temperatures of similar to 228 degrees to 249 degrees C. Mineralization is dominated by pyrite-marcasite-barite-anhydrite. Radiometric dating using the Ra-228/Ra-226 and Ra-226/Ba methods shows active chimneys to be {\textless}20 with most {\textless}2 years old. However, the chimneys at Clark show evidence for mixing with, and remobilizing of, barite as old as 19,000 years. This is consistent with Nd and Sr isotope compositions of Clark chimney and sulfate crust samples that indicate mixing of similar to 40{\%} seawater with a vent fluid derived from low K lavas. Similarly, REE data show the hydrothermal fluids have interacted with a plagioclase-rich source rock. A holistic approach to the study of the Clark hydrothermal system has revealed a two-stage process whereby a caldera-forming volcanic event preceded a later cone-building event. This ensured a protracted (at least 20 ka yrs) history of hydrothermal activity and associated mineral deposition. If we assume at least 200-m-high walls for the postulated (buried) caldera, then hydrothermal fluids would have exited the seafloor 20 ka years ago at least 550 m deeper than they do today, with fluid discharge temperatures potentially much hotter (similar to 350 degrees C). Subsequent to caldera infilling, relatively porous volcaniclastic and other units making up the cone acted as largescale filters, enabling ascending hydrothermal fluids to boil and mix with seawater subseafloor, effectively removing the metals (including remobilized Cu) in solution before they reached the seafloor. This has implications for estimates for the metal inventory of seafloor hydrothermal systems pertaining to arc hydrothermal systems.},
	keywords = {AUV ABE (Autonomous Benthic Explorer), AUV Sentry (Autonomous Underwater Vehicle)},
	issn = {0361-0128},
	author = {de Ronde, C E J and Walker, S L and Ditchburn, R G and Tontini, F Caratori and Hannington, M D and Merle, S G and Timm, C and Handler, M R and Wysoczanski, R J and Dekov, V M and Kamenov, G D and Baker, E T and Embley, R W and Lupton, J E and Stoffers, P}
}
@article {Goss2010,
	title = {{Geochemistry of lavas from the 2005-2006 eruption at the East Pacific Rise, 9 degrees 46{\textquoteright}N-9 degrees 56{\textquoteright}N: Implications for ridge crest plumbing and decadal changes in magma chamber compositions}},
	journal = {Geochemistry, Geophysics, Geosystems},
	volume = {11},
	year = {2010},
	pages = {Q05T09},
	abstract = {Detailed mapping, sampling, and geochemical analyses of lava flows erupted from an \~{}18 km long section of the northern East Pacific Rise (EPR) from 9{\textdegree}46'N to 9{\textdegree}56'N during 2005{\textendash}2006 provide unique data pertaining to the short-term thermochemical changes in a mid-ocean ridge magmatic system. The 2005{\textendash}2006 lavas are typical normal mid-oceanic ridge basalt with strongly depleted incompatible trace element patterns with marked negative Sr and Eu/Eu* anomalies and are slightly more evolved than lavas erupted in 1991{\textendash}1992 at the same location on the EPR. Spatial geochemical differences show that lavas from the northern and southern limits of the 2005{\textendash}2006 eruption are more evolved than those erupted in the central portion of the fissure system. Similar spatial patterns observed in 1991{\textendash}1992 lavas suggest geochemical gradients are preserved over decadal time scales. Products of northern axial and off-axis fissure eruptions are consistent with the eruption of cooler, more fractionated lavas that also record a parental melt component not observed in the main suite of 2005{\textendash}2006 lavas. Radiogenic isotopic ratios for 2005{\textendash}2006 lavas fall within larger isotopic fields defined for young axial lavas from 9{\textdegree}N to 10{\textdegree}N EPR, including those from the 1991{\textendash}1992 eruption. Geochemical data from the 2005{\textendash}2006 eruption are consistent with an invariable mantle source over the spatial extent of the eruption and petrogenetic processes (e.g., fractional crystallization and magma mixing) operating within the crystal mush zone and axial magma chamber (AMC) before and during the 13 year repose period. Geochemical modeling suggests that the 2005{\textendash}2006 lavas represent differentiated residual liquids from the 1991{\textendash}1992 eruption that were modified by melts added from deeper within the crust and that the eruption was not initiated by the injection of hotter, more primitive basalt directly into the AMC. Rather, the eruption was driven by AMC pressurization from persistent or episodic addition of more evolved magma from the crystal mush zone into the overlying subridge AMC during the period between the two eruptions. Heat balance calculations of a hydrothermally cooled AMC support this model and show that continual addition of melt from the mush zone was required to maintain a sizable AMC over this time interval.},
	keywords = {HOV Alvin (Human Occupied Vehicle)},
	issn = {1525-2027},
	doi = {10.1029/2009GC002977},
	url = {http://dx.doi.org/10.1029/2009GC002977},
	author = {Goss, A R and Perfit, M R and Ridley, W I and Rubin, K H and Kamenov, G D and Soule, S A and Fundis, A and Fornari, D J}
}
