@article {651853,
	title = {The spatial footprint of hydrothermal scavenging on 230ThXS-derived mass accumulation rates},
	journal = {Geochimica et Cosmochimica Acta},
	year = {2020},
	abstract = {Mid-ocean ridges are valuable archives of sedimentary flux records used to investigate atmospheric, oceanographic, and solid Earth responses to climate variability. Constant flux proxies, such as extraterrestrial helium-3 (3HeET) and excess thorium-230 (230ThXS), constrain vertical mass accumulation rates independent of the biases associated with lateral sediment transport and age model resolution. However, thorium scavenging by hydrothermal particles can perturb local\&nbsp;230ThXS\&nbsp;deposition and complicate its application as a constant flux proxy in near-ridge environments. We characterize the footprint of hydrothermal scavenging on sedimentary\&nbsp;230ThXS\&nbsp;using coupled\&nbsp;3HeET-230ThXS\&nbsp;analyses in cores from the Mid-Atlantic Ridge and the Juan de Fuca Ridge. Samples deposited \&gt;10 km from the Juan de Fuca Ridge indicate reliable off-axis behavior of both constant flux proxies. In contrast, samples deposited \&lt;10 km from the Juan de Fuca Ridge axis and within the axial valley of the Mid-Atlantic Ridge suggest 50{\textendash}80\% deficits in sedimentary\&nbsp;230ThXS\&nbsp;relative to its production rate. These deficits contrast with sedimentary\&nbsp;230ThXS\&nbsp;surpluses recently observed on the East Pacific Rise. The spatial footprint of hydrothermal scavenging varies globally and temporally, likely as a function of the intensity of local hydrothermal activity. The combined ridge data suggest that near-vent sediments (typically within \~{}5 km, but variable by ridge) receive relatively high\&nbsp;230ThXS\&nbsp;deposition rates as a direct result of hydrothermal particle scavenging, while more distal sediments receive relatively low\&nbsp;230ThXS\&nbsp;deposition rates due to diffusive loss of overlying seawater\&nbsp;230ThXS\&nbsp;towards the vent. Aside from the East Pacific Rise, far-field sediments are likely to exhibit typical\&nbsp;230ThXS\&nbsp;deposition rates at distances greater than \~{}10 km of the ridge axis. However,\&nbsp;230ThXS\&nbsp;systematics within the axial valleys of slow-spreading ridges may be complicated by other factors. Combined\&nbsp;3HeET-230ThXS\&nbsp;studies at multiple ridges are needed to further characterize the nature of hydrothermal scavenging and to evaluate the potential of sedimentary\&nbsp;230ThXS\&nbsp;anomalies to record large-scale variability in past hydrothermal activity.},
	url = {https://www.sciencedirect.com/science/article/abs/pii/S0016703720300193},
	author = {Middleton, JL and S. Mukhopadhyay and KM Costa and FJ Pavia and Winckler, G and McManus, JF and M D{\textquoteright}Almeida and Langmuir, C.H. and PJ Huybers}
}
