Abstract. High-resolution geochronology is essential for determining the growth rate of volcanoes, which is one of the key factors for establishing the periodicity of volcanic eruptions. However, there are less high-resolution eruptive histories (> 106 years) determined for long-lived submarine arc volcanic complexes than for subaerial complexes, since submarine volcanoes are far more difficult to observe than subaerial ones. In this study, high-resolution geochronology and major-element data are presented for the Milos volcanic field (VF) in the South Aegean Volcanic Arc, Greece. The Milos VF has been active for over 3 Myr, and the first 2 × 106 years of its eruptive history occurred in a submarine setting that has been emerged above sea level. The long submarine volcanic history of the Milos VF makes it an excellent natural laboratory to study the growth rate of a long-lived submarine arc volcanic complex. This study reports 21 new high-precision 40Ar/39Ar ages and major-element compositions for 11 volcanic units of the Milos VF. This allows us to divide the Milos volcanic history into at least three periods of different long-term volumetric volcanic output rate (Qe). Periods I (submarine, ∼ 3.3–2.13 Ma) and III (subaerial, 1.48 Ma–present) have a low Qe of 0.9 ± 0.5 × 10−5 and 0.25 ± 0.05 × 10−5 km3 yr−1, respectively. Period II (submarine, 2.13–1.48 Ma) has a 3–12 times higher Qe of 3.0 ± 1.7 × 10−5 km3 yr−1. The Qe of the Milos VF is 2–3 orders of magnitude lower than the average for rhyolitic systems and continental arcs.
Melt inclusions (MIs) in deeply formed magmatic minerals are typically characterised by larger variability in major and trace element- and isotope compositions compared to bulk lavas. The larger geochemical variability reflects that MIs represent partial melts that have escaped post-entrapment melt mixing that homogenises bulk lava compositions. Thus melt inclusions more realistically record the compositional heterogeneity of a mantle source and can be used to infer the presence of enriched or depleted source components in various tectonic settings. Recent development of 10^13 Ω resistors in the feedback loop of Faraday cup amplifiers used in thermal ionisation mass spectrometry (TIMS) [1] now allows determining combined Sr-Nd-Pb isotopes in individual melt inclusions (<300 µm). Data on MIs from peninsular Italy confirm the strength of these techniques to identify source components previously unresolved by bulk lava geochemistry [2, 3]. We further optimised the combined wet chemistry and TIMS analytical techniques applied to individual olivine- hosted melt inclusions to determine coupled 1) trace element ratios by ICPMS; 2) Sr-Nd-Pb concentrations by isotope dilution; and 3) isotopic compositions by TIMS. For Pb isotope analyses we use an optimised 207Pb–204Pb double spike technique [4]. Total procedural blanks (<20 pg Sr; <1 pg Nd; <10 pg Pb) can be corrected for using the analysed isotope compositions, but currently are the main limiting factor for application to tectonic settings that generate more depleted magma compositions. The improved procedures along with data on reference materials and melt inclusions from the Roman Magmatic Province in Italy are presented to evaluate the accuracy and reproducibility as a function of the amount of material analysed.
Three cleaning techniques that remove external contamination of human hair are assessed to investigate the potential use of Sr and Pb isotope composition of hair for human provenancing. These techniques are; (i) a centrifugation technique using diiodomethane where hair and soil particles are separated by density difference; (ii) a leaching technique of the hair surface using 2 M HNO3 acid and (iii) cleaning the hair with chloroform, methanol and ultra pure water. These techniques are validated and are successfully applied to demonstrate the capability of modern and archaeological human scalp hair and modern human facial hair to record Sr and Pb isotope variations related to geographic location. In this study, Sr isotope ratios analysed in modern human scalp hair from a female vegetarian and non-smoker register marked isotopic change on a monthly timescale when an individual moves to locations with contrasting Sr isotope compositions. Pb isotope ratios do not show significant changes after moving locations, possibly due to comparable Pb isotope ratios in the two environments. In contrast, Pb isotopes ratios analysed in facial hair from a male omnivore and smoker record isotopic changes within a two week period when moving between locations with significant differences in environmental Pb isotope compositions. Further research is needed to determine the exact rate of change in isotopic composition in scalp and facial hair in humans with different diets and life styles that move from geographical locations with isotopic contrasting composition.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)
'/%3e%3c/defs%3e%3cpath fill='%23012169' d='M0 0h10080v5040H0z'/%3e%3cpath stroke='%23fff' stroke-width='.6' d='m0 0 6 3m0-3L0 3' clip-path='url(%23b)' transform='scale(840)'/%3e%3cpath stroke='%23e4002b' stroke-width='.4' d='m0 0 6 3m0-3L0 3' clip-path='url(%23c)' transform='scale(840)'/%3e%3cpath stroke='%23fff' stroke-width='840' d='M2520 0v2520M0 1260h5040'/%3e%3cpath stroke='%23e4002b' stroke-width='504' d='M2520 0v2520M0 1260h5040'/%3e%3cg fill='%23fff'%3e%3cuse xlink:href='%23d' x='2520' y='3780'/%3e%3cuse xlink:href='%23a' x='7560' y='4200'/%3e%3cuse xlink:href='%23a' x='6300' y='2205'/%3e%3cuse xlink:href='%23a' x='7560' y='840'/%3e%3cuse xlink:href='%23a' x='8680' y='1869'/%3e%3cuse xlink:href='%23e' x='8064' y='2730'/%3e%3c/g%3e%3c/svg%3e)
