Chemical and isotope composition of rocks from the Omgon Range, Western Kamchatka coastal area

Hypabyssal rocks of the Omgon Range, Western Kamchatka that intrude Upper Albian-Lower Campanian deposits of the Eurasian continental margin belong to three coeval (62.5-63.0 Ma) associations: (1) ilmenite gabbro-dolerites, (2) titanomagnetite gabbro-dolerites and quartz microdiorites, and (3) porphyritic biotite granites and granite-aplites. Early Paleocene age of ilmenite gabbro-dolerites and biotite granites was confirmed by zircon and apatite fission-track dating. Ilmenite and titanomagnetite gabbro-dolerites were produced by multilevel fractional crystallization of basaltic melts with, respectively, moderate and high Fe-Ti contents and contamination of these melts with rhyolitic melts of different compositions. Moderate- and high-Fe-Ti basaltic melts were derived from mantle spinel peridotite variably depleted and metasomatized by slab-derived fluid prior to melting. The melts were generated at variable depths and different degrees of melting. Biotite granites and granite aplites were produced by combined fractional crystallization of a crustal rhyolitic melt and its contamination with terrigenous rocks of the Omgon Group. The rhyolitic melts were likely derived from metabasaltic rocks of suprasubduction nature. Early Paleocene hypabyssal rocks of the Omgon Range were demonstrated to have been formed in an extensional environment, which dominated in the margin of the Eurasian continent from Late Cretaceous throughout Early Paleocene. Extension in the Western Kamchatka segment preceded the origin of the Western Koryakian-Kamchatka (Kinkil') continental-margin volcanic belt in Eocene time. This research was conducted based on original geological, mineralogical, geochemical, and isotopic (Rb-Sr) data obtained by the authors.

Glacier mass balances of Stubacher Sonnblickkees, Hohe Tauern Range, Eastern Alps, Austria, 1958/1959 to 2012/2013

Stubacher Sonnblickkees (SSK) is located in the Hohe Tauern Range (Eastern Alps) in the south of Salzburg Province (Austria) in the region of Oberpinzgau in the upper Stubach Valley. The glacier is situated at the main Alpine crest and faces east, starting at elevations close to 3050 m and in the 1980s terminated at 2500 m a.s.l. It had an area of 1.7 km² at that time, compared with 1 km² in 2013. The glacier type can be classified as a slope glacier, i.e. the relief is covered by a relatively thin ice sheet and there is no regular glacier tongue. The rough subglacial topography makes for a complex shape in the surface topography, with various concave and convex patterns. The main reason for selecting this glacier for mass balance observations (as early as 1963) was to verify on a complex glacier how the mass balance methods and the conclusions - derived during the more or less pioneer phase of glaciological investigations in the 1950s and 1960s - could be applied to the SSK glacier. The decision was influenced by the fact that close to the SSK there was the Rudolfshütte, a hostel of the Austrian Alpine Club (OeAV), newly constructed in the 1950s to replace the old hut dating from 1874. The new Alpenhotel Rudolfshütte, which was run by the Slupetzky family from 1958 to 1970, was the base station for the long-term observation; the cable car to Rudolfshütte, operated by the Austrian Federal Railways (ÖBB), was a logistic advantage. Another factor for choosing SSK as a glaciological research site was the availability of discharge records of the catchment area from the Austrian Federal Railways who had turned the nearby lake Weißsee ('White Lake') - a former natural lake - into a reservoir for their hydroelectric power plants. In terms of regional climatic differences between the Central Alps in Tyrol and those of the Hohe Tauern, the latter experienced significantly higher precipitation , so one could expect new insights in the different response of the two glaciers SSK and Hintereisferner (Ötztal Alps) - where a mass balance series went back to 1952. In 1966 another mass balance series with an additional focus on runoff recordings was initiated at Vernagtfener, near Hintereisferner, by the Commission of the Bavarian Academy of Sciences in Munich. The usual and necessary link to climate and climate change was given by a newly founded weather station (by Heinz and Werner Slupetzky) at the Rudolfshütte in 1961, which ran until 1967. Along with an extension and enlargement to the so-called Alpine Center Rudolfshütte of the OeAV, a climate observatory (suggested by Heinz Slupetzky) has been operating without interruption since 1980 under the responsibility of ZAMG and the Hydrological Service of Salzburg, providing long-term met observations. The weather station is supported by the Berghotel Rudolfshütte (in 2004 the OeAV sold the hotel to a private owner) with accommodation and facilities. Direct yearly mass balance measurements were started in 1963, first for 3 years as part of a thesis project. In 1965 the project was incorporated into the Austrian glacier measurement sites within the International Hydrological Decade (IHD) 1965 - 1974 and was afterwards extended via the International Hydrological Program (IHP) 1975 - 1981. During both periods the main financial support came from the Hydrological Survey of Austria. After 1981 funds were provided by the Hydrological Service of the Federal Government of Salzburg. The research was conducted from 1965 onwards by Heinz Slupetzky from the (former) Department of Geography of the University of Salzburg. These activities received better recognition when the High Alpine Research Station of the University of Salzburg was founded in 1982 and brought in additional funding from the University. With recent changes concerning Rudolfshütte, however, it became unfeasible to keep the research station going. Fortunately, at least the weather station at Rudolfshütte is still operating. In the pioneer years of the mass balance recordings at SSK, the main goal was to understand the influence of the complicated topography on the ablation and accumulation processes. With frequent strong southerly winds (foehn) on the one hand, and precipitation coming in with storms from the north to northwest, the snow drift is an important factor on the undulating glacier surface. This results in less snow cover in convex zones and in more or a maximum accumulation in concave or flat areas. As a consequence of the accentuated topography, certain characteristic ablation and accumulation patterns can be observed during the summer season every year, which have been regularly observed for many decades . The process of snow depletion (Ausaperung) runs through a series of stages (described by the AAR) every year. The sequence of stages until the end of the ablation season depends on the weather conditions in a balance year. One needs a strong negative mass balance year at the beginning of glacier measurements to find out the regularities; 1965, the second year of observation resulted in a very positive mass balance with very little ablation but heavy accumulation. To date it is the year with the absolute maximum positive balance in the entire mass balance series since 1959, probably since 1950. The highly complex ablation patterns required a high number of ablation stakes at the beginning of the research and it took several years to develop a clearer idea of the necessary density of measurement points to ensure high accuracy. A great number of snow pits and probing profiles (and additional measurements at crevasses) were necessary to map the accumulation area/patterns. Mapping the snow depletion, especially at the end of the ablation season, which coincides with the equilibrium line, is one of the main basic data for drawing contour lines of mass balance and to calculate the total mass balance (on a regular-shaped valley glacier there might be an equilibrium line following a contour line of elevation separating the accumulation area and the ablation area, but not at SSK). - An example: in 1969/70, 54 ablation stakes and 22 snow pits were used on the 1.77 km² glacier surface. In the course of the study the consistency of the accumulation and ablation patterns could be used to reduce the number of measurement points. - At the SSK the stratigraphic system, i.e. the natural balance year, is used instead the usual hydrological year. From 1964 to 1981, the yearly mass balance was calculated by direct measurements. Based on these records of 17 years, a regression analysis between the specific net mass balance and the ratio of ablation area to total area (AAR) has been used since then. The basic requirement was mapping the maximum snow depletion at the end of each balance year. There was the advantage of Heinz Slupetzky's detailed local and long-term experience, which ensured homogeneity of the series on individual influences of the mass balance calculations. Verifications took place as often as possible by means of independent geodetic methods, i.e. monoplotting , aerial and terrestrial photogrammetry, more recently also the application of PHOTOMODELLER and laser scans. The semi-direct mass balance determinations used at SSK were tentatively compared with data from periods of mass/volume change, resulting in promising first results on the reliability of the method. In recent years re-analyses of the mass balance series have been conducted by the World Glacier Monitoring Service and will be done at SSK too. - The methods developed at SSK also add to another objective, much discussed in the 1960s within the community, namely to achieve time- and labour-saving methods to ensure continuation of long-term mass balance series. The regression relations were used to extrapolate the mass balance series back to 1959, the maximum depletion could be reconstructed by means of photographs for those years. R. Günther (1982) calculated the mass balance series of SSK back to 1950 by analysing the correlation between meteorological data and the mass balance; he found a high statistical relation between measured and determined mass balance figures for SSK. In spite of the complex glacier topography, interesting empirical experiences were gained from the mass balance data sets, giving a better understanding of the characteristics of the glacier type, mass balance and mass exchange. It turned out that there are distinct relations between the specific net balance, net accumulation (defined as Bc/S) and net ablation (Ba/S) to the AAR, resulting in characteristic so-called 'turnover curves'. The diagram of SSK represents the type of a glacier without a glacier tongue. Between 1964 and 1966, a basic method was developed, starting from the idea that instead of measuring years to cover the range between extreme positive and extreme negative yearly balances one could record the AAR/snow depletion/Ausaperung during one or two summers. The new method was applied on Cathedral Massif Glacier, a cirque glacier with the same area as the Stubacher Sonnblickkees, in British Columbia, Canada. during the summers of 1977 and 1978. It returned exactly the expected relations, e.g. mass turnover curves, as found on SSK. The SSK was mapped several times on a scale of 1:5000 to 1:10000. Length variations have been measured since 1960 within the OeAV glacier length measurement programme. Between 1965 and 1981, there was a mass gain of 10 million cubic metres. With a time lag of 10 years, this resulted in an advance until the mid-1980s. Since 1982 there has been a distinct mass loss of 35 million cubic metres by 2013. In recent years, the glacier has disintegrated faster, forced by the formation of a periglacial lake at the glacier terminus and also by the outcrops of rocks (typical for the slope glacier type), which have accelerated the meltdown. The formation of this lake is well documented. The glacier has retreated by some 600 m since 1981. - Since August 2002, a runoff gauge installed by the Hydrographical Service of Salzburg has recorded the discharge of the main part of SSK at the outlet of the new Unterer Eisboden See. The annual reports - submitted from 1982 on as a contractual obligation to the Hydrological Service of Salzburg - document the ongoing processes on the one hand, and emphasize the mass balance of SSK and outline the climatological reasons, mainly based on the met-data of the observatory Rudolfshütte, on the other. There is an additional focus on estimating the annual water balance in the catchment area of the lake. There are certain preconditions for the water balance equation in the area. Runoff is recorded by the ÖBB power stations, the mass balance of the now approx. 20% glaciated area (mainly the Sonnblickkees) is measured andthe change of the snow and firn patches/the water content is estimated as well as possible. (Nowadays laserscanning and ground radar are available to measure the snow pack). There is a net of three precipitation gauges plus the recordings at Rudolfshütte. The evaporation is of minor importance. The long-term annual mean runoff depth in the catchment area is around 3.000 mm/year. The precipitation gauges have measured deficits between 10% and 35%, on average probably 25% to 30%. That means that the real precipitation in the catchment area Weißsee (at elevations between 2,250 and 3,000 m) is in an order of 3,200 to 3,400 mm a year. The mass balance record of SSK was the first one established in the Hohe Tauern region (and now since the Hohe Tauern National Park was founded in 1983 in Salzburg) and is one of the longest measurement series worldwide. Great efforts are under way to continue the series, to safeguard against interruption and to guarantee a long-term monitoring of the mass balance and volume change of SSK (until the glacier is completely gone, which seems to be realistic in the near future as a result of the ongoing global warming). Heinz Slupetzky, March 2014

A comprehensive analysis of tidal notches in the Mediterranean Sea

Recent works (Evelpidou et al., 2012) suggest that the modern tidal notch is disappearing worldwide due sea level rise over the last century. In order to assess this hypothesis, we measured modern tidal notches in several of sites along the Mediterranean coasts. We report observations on tidal notches cut along carbonate coasts from 73 sites from Italy, France, Croatia, Montenegro, Greece, Malta and Spain, plus additional observations carried outside the Mediterranean. At each site, we measured notch width and depth, and we described the characteristics of the biological rim at the base of the notch. We correlated these parameters with wave energy, tide gauge datasets and rock lithology. Our results suggest that, considering 'the development of tidal notches the consequence of midlittoral bioerosion' (as done in Evelpidou et al., 2012) is a simplification that can lead to misleading results, such as stating that notches are disappearing. Important roles in notch formation can be also played by wave action, rate of karst dissolution, salt weathering and wetting and drying cycles. Of course notch formation can be augmented and favoured also by bioerosion which can, in particular cases, be the main process of notch formation and development. Our dataset shows that notches are carved by an ensemble rather than by a single process, both today and in the past, and that it is difficult, if not impossible, to disentangle them and establish which one is prevailing. We therefore show that tidal notches are still forming, challenging the hypothesis that sea level rise has drowned them.

U-Pb, trace element, and Hf isotope analysis for Macquarie Island detrital zircon

Oceanic zircon trace element and Hf-isotope geochemistry offers a means to assess the magmatic evolution of a dying spreading ridge and provides an independent evaluation of the reliability of oceanic zircon as an indicator of mantle melting conditions. The Macquarie Island ophiolite in the Southern Ocean provides a unique testing ground for this approach due to its formation within a mid-ocean ridge that gradually changed into a transform plate boundary. Detrital zircon recovered from the island records this change through a progressive enrichment in incompatible trace elements. Oligocene age (33-27 Ma) paleo-detrital zircon in ophiolitic sandstones and breccias interbedded with pillow basalt have trace element compositions akin to a MORB crustal source, whereas Late Miocene age (8.5 Ma) modern-detrital zircon collected from gabbroic colluvium on the island have highly enriched compositions unlike typical oceanic zircon. This compositional disparity between age populations is not complimented by analytically equivalent eHf data that primarily ranges from 14 to 13 for sandstone and modern-detrital populations. A wider compositional range for the sandstone population reflects a multiple pluton source provenance and is augmented by a single cobble clast with eHf equivalent to the maximum observed composition in the sandstone (~17). Similar sandstone and colluvium Hf-isotope signatures indicate inheritance from a similar mantle reservoir that was enriched from the depleted MORB mantle average. The continuity in Hf-isotope signature relative to trace element enrichment in Macquarie Island zircon populations, suggests the latter formed by reduced partial melting linked to spreading-segment shortening and transform lengthening along the dying spreading ridge.

Chemical analysis of ash layers in ODP Leg 104 holes

Numerous fresh ash layers comprise about 0.3% by volume of Neogene to Holocene sediments drilled at Leg 104 Sites 642 and 643 (Vøring Plateau, North Atlantic). Median grain sizes of the ashes are about 100 /µm and maximum grain sizes range up to 1200 µm. Rhyolitic pumice shards dominate, with minor bubble wall shards. Basaltic shards are poorly vesicular and blocky or round. Phenocrystic plagioclase, zircon, and clinopyroxene occur in the rhyolitic, plagioclase, and clinopyroxene phenocrysts and basaltic lithics in the basaltic tephra. Quartz, amphibole, clinozoisite, and rutile are interpreted as xenocrysts. All ash layers are well-sorted and represent distal fallout from major explosive eruptions. Most ashes are rhyolitic (high-K and low-K) in composition, some are bimodal (tholeiitic and rhyolitic). Early Miocene tephra is dominantly basaltic. Iceland is inferred to be the likely source region for most ashes. Late Miocene high-K rhyolites may have originated from the K-rich Jan Mayen magmatic province. One Quaternary layer with biotite and alkali feldspar phenocrysts may have been derived from Jan Mayen Island. Four individual Pliocene to Holocene ash layers from Sites 642 and 643 can be correlated fairly well. Upper Miocene layers are tentatively correlated as a sequence between Sites 642 and 643. Average calculated layer frequencies are about three layers/m.y. through the Pliocene and Pleistocene and five to eight layers per m.y. through the middle and late Miocene, suggesting rather continuous volcanic activity in the North Atlantic. Episodic magmatic activity during Neogene epochs in this part of the North Atlantic, as postulated in the literature, cannot be confirmed.

Chemical analysis of various geological samples from Northern Victoria Land, Antarctica

This paper reports the results of a preliminary palaeomagnetic investigation of the Admiralty Intrusives complex of northern Victoria Land, Antarctica. The samples were collected at Mt. Supernal and Inferno Peak, two pinions mainly formed of granodiorite and minor tonalite and emplaced at ab. 350 Ma at a high crustal level, as shown by amphibole geobarometric data and occurrence of miarolitic cavities. Microprobe and isothermal remanence analyses showed that magnetite. characterized by low coercivity and Curic point in the range 550-570 °C is the only primary ferromagnetic mineral. Stepwise thermaldemagnetization succeeded in isolatingamagnetization component. stable up to 530 °C. The virtual geomagnetic poles (VGPs) of the two plutons are different. That of Inferno Peak is consistent with the Australian palaeopoles of late Devonian-early Carboniferous age, whereas the location of the Mt. Supernal VGP probably results from the tectonic activity which affected the Ross Sea region during the Cenozoic.

Geochemical analysis of sediments and interstitial water in sediment cores from the North-West African continental margin and from the Central Pacific

A. Continental slope sediments off Spanish-Sahara and Senegal contain up to 4% organic carbon and up to 0.4% total nitrogen. The highest concentrations were found in sediments from water depths between 1000 and 2000 m. The regional and vertical distribution of organic matter differs significantly. Off Spanish-Sahara the organic matter content of sediment deposited during glacial times (Wuerm, Late Riss) is high whereas sediments deposited during interglacial times (Recent, Eem) are low in organic matter. Opposite distribution was found in sediments off Senegal. The sediments contain 30 to 130 ppm of fixed nitrogen. In most sediments this corresponds to 2-8 % of the total nitrogen. Only in sediments deposited during interglacial times off Spanish-Sahara up to 20 % of the total nitrogen is contained as inorganically bound nitrogen. Positive correlations of the fixed nitrogen concentrations to the amounts of clay, alumina, and potassium suggest that it is primarily fixed to illites. The amino acid nitrogen and hexosamine nitrogen account for 17 to 26 % and 1.3 to 2.4 %, respectively of the total nitrogen content of the sediments. The concentrations vary between 200 and 850 ppm amino acid nitrogen and 20 to 70 ppm hexosamine nitrogen, both parallel the fluctiations of organic matter in the sediment. Fulvic acids, humic acids, and the total organic matter of the sediments may be clearly differentiated from one another and their amino acid and hexosamine contents and their amino acid composition: a) Fulvic acids contain only half as much amino acids as humic acids b) The molar amino acid/hexosamine ratios of the fulvic acids are half those of the humic acids and the total organic matter of the sediment c) The amino acid spectra of fulvic acids are characterized by an enrichment of aspartic acid, alanine, and methionine sulfoxide and a depletion of glycine, valine, isoleucine, leucine, tyrosine, phenylalanine, lysine, and arginine compared to the spectra of the humic acids and those of the total organic matter fraction of the sediment. d) The amino acid spectra of the humic acids and those of the total organic matter fraction of the sediments are about the same with the exception that arginine is clearly enriched in the total organic matter. In general, as indicated by the amino compounds humic acids resemble closer the total organic matter composition than the low molecular fulvic acids do. This supports the general idea that during the course of diagenesis in reducing sediments organic matter stabilizes from a fulvic-like structure to humic-like structure and finally to kerogen. The decomposition rates of single aminio acids differ significantly from one another. Generally amino acids which are preferentially contained in humic acids and the total organic matter fraction show a smaller loss with time than those preferably well documented in case of the basic amino acids lysine and arginine which- although thermally unstable- are the most stable amino acids in the sediments. A favoured incorporation of these compounds into high molecular substances as well as into clay minerals may explain their relatively high "stability" in the sediment. The nitrogen loss from the sediments due to the activity of sulphate-reducing bacteria amounts to 20-40 % of the total organic nitrogen now present. At least 40 % of the organic nitrogen which is liberated by sulphate-reducing bacteria can be explained ny decomposition of amino acids alone. B. Deep-sea sediments from the Central Pacific The deep-seas sediments contain 1 to 2 orders of magnitude less organic matter than the continental slope sediments off NW Africa, i.e. 0.04 to 0.3 % organic carbon. The fixed nitrogen content of the deep-sea sediments ranges from 60 to 270 ppm or from 20 to 45 % of the total nitrogen content. While ammonia is the prevailing inorganic nitrogen compound in anoxic pore waters, nitrate predominates in the oxic environment of the deep-sea sediments. Near the sediment/water interface interstital nitrate concentrations of around 30 µg-at. N/l were recorded. These generally increase with sediment depth by 10 to 15 µg-at. NO3- N/l. This suggests the presence of free oxygen and the activity of nitrifying bacteria in the interstitial waters. The ammonia content of the interstitial water of the oxic deep-sea sediments ranges from 2 to 60 µg-at. N/l and thus is several orders of magnitude less than in anoxic sediments. In contrast to recorded nitrate gradients towards the sediments/water interface, there are no ammonia concentration gradients. However, ammonia concentrations appear to be characteristic for certain regional areas. It is suggested that this regional differentiation is caused by ion exchange reactions involving potassium and ammonium ions rather than by different decomposition rates of organic matter. C. C/N ratios All estimated C/N ratios of surface sediments vary between 3 and 9 in the deep-sea and the continental margin, respectively. Whereas the C/N ratios generally increase with depth in the sediment cores off NW Africa they decrease in the deep-sea cores. The lowest values of around 1.3 were found in the deeper sections of the deep-sea cores, the highest of around 10 in the sediments off NW Africa. The wide range of the C/N ratios as well as their opposite behaviour with increasing sediment depth in both the deep-sea and continental margin sediment cores, can be attributed mainly to the combination of the following three factors: 1. Inorganic and organic substances bound within the latticed of clay minerals tend to decrease the C/N ratios. 2. Organic matter not protected by absorption on the clay minerals tends to increase C/N ratios 3. Diagenetic alteration of organic matter by micro-organisms tends to increase C/N ratios through preferential loss of nitrogen The diagenetic changes of the microbially decomposable organic matter results in both oxic and anoxic environments in a preferential loss of nitrogen and hence in higher C/N ratios of the organic fraction. This holds true for most of the continental margin sediments off NW Africa which contain relatively high amounts of organic matter so that factors 2 and 3 predominate there. The relative low C/N ratios of the sediments deposited during interglacial times off Spanish-Sahara, which are low in organic carbon, show the increasing influence of factor 1 - the nitrogen-rich organic substances bound to clay minerals. In the deep-sea sediments from the Central Pacific this factor completely predominates so that the C/N rations of the sediments approach that of the substance absorbed to clay minerals with decreasing organic matter content. In the deeper core sections the unprotected organic matter has been completely destroyed so that the C/N ratios of the total sediments eventually fall into the same range as those of the pure clay mineral fraction.

Geospatial analysis of groundwater depth for manual well drilling suitability in the Zinder Region, Niger

Manual and low-tech well drilling techniques have potential to assist in reaching the United Nations' millennium development goal for water in sub-Saharan Africa. This study used publicly available geospatial data in a regression tree analysis to predict groundwater depth in the Zinder region of Niger to identify suitable areas for manual well drilling. Regression trees were developed and tested on a database for 3681 wells in the Zinder region. A tree with 17 terminal leaves provided a range of ground water depth estimates that were appropriate for manual drilling, though much of the tree's complexity was associated with depths that were beyond manual methods. A natural log transformation of groundwater depth was tested to see if rescaling dataset variance would result in finer distinctions for regions of shallow groundwater. The RMSE for a log-transformed tree with only 10 terminal leaves was almost half that of the untransformed 17 leaf tree for groundwater depths less than 10 m. This analysis indicated important groundwater relationships for commonly available maps of geology, soils, elevation, and enhanced vegetation index from the MODIS satellite imaging system.

Sedimentological and palynological analysis of sediment cores from the northeastern Vietnamese Mekong River Delta

Three radiocarbon-dated sediment cores from the northeastern Vietnamese Mekong River Delta have been analysed with a multiproxy approach (grain size, pollen and spores, macro-charcoal, carbon content) to unravel the palaeoenvironmental history of the region since the mid Holocene. During the mid-Holocene sea-level highstand a diverse, zoned and widespread mangrove belt (dominated by Rhizophora) covered the extended tidal flats. The subsequent regression and coeval delta progradation led to the rapid development of a back-mangrove community dominated by Ceriops and Bruguiera but also represented locally by e.g. Kandelia, Excoecaria and Phoenix. Along rivers this community seems to have endured even when the adjoining floodplain had already shifted to freshwater vegetation. Generally this freshwater vegetation has a strong swamp signature but locally Arecaceae, Fabaceae, Moraceae/Urticaceae and Myrsinaceae are important and mirror the geomorphological diversity of the delta plain. The macro-charcoal record implies that natural burning of vegetation occurred throughout the records, however, the occurrence of the highest amounts of macro-charcoal particles is linked with modern human activity.

Utility of thallium and geochemical analysis of Mariana arc sediments from ODP Hole 129-801A and 129-801B

We provide the first exploration of thallium (Tl) abundances and stable isotope compositions as potential tracers during arc lava genesis. We present a case study of lavas from the Central Island Province (CIP) of the Mariana arc, supplemented by representative sedimentary and altered oceanic crust (AOC) inputs from ODP Leg 129 Hole 801 outboard of the Mariana trench. Given the large Tl concentration contrast between the mantle and subduction inputs coupled with previously published distinctive Tl isotope signatures of sediment and AOC, the Tl isotope system has great potential to distinguish different inputs to arc lavas. Furthermore, CIP lavas have well-established inter island variability, providing excellent context for the examination of Tl as a new stable isotope tracer. In contrast to previous work (Nielsen et al., 2006b), we do not observe Tl enrichment or light epsilon 205Tl (where epsilon 205Tl is the deviation in parts per 10,000 of a sample 205Tl/203Tl ratio compared to NIST SRM 997 Tl standard) in the Jurassic-aged altered mafic ocean crust subducting outboard of the Marianas (epsilon 205Tl = - 4.4 to 0). The lack of a distinctive epsilon 205Tl signature may be related to secular changes in ocean chemistry. Sediments representative of the major lithologies from ODP Hole Leg 129 801 have 1-2 orders of magnitude of Tl enrichment compared to the CIP lavas, but do not record heavy signatures (epsilon 205Tl = - 3.0 to + 0.4), as previously found in similar sediment types (epsilon 205Tl > + 2.5; Rehkämper et al., 2004). We find a restricted range of epsilon 205Tl = - 1.8 to - 0.4 in CIP lavas, which overlaps with MORB. One lava from Guguan falls outside this range with epsilon 205Tl = + 1.2. Coupled Cs, Tl and Pb systematics of Guguan lavas suggests that this heavy Tl isotope composition may be due to preferential degassing of isotopically light Tl. In general, the low Tl concentrations and limited isotopic range in the CIP lavas is likely due to the unexpectedly narrow range of epsilon 205Tl found in Mariana subduction inputs, coupled with volcaniclastic, rather than pelagic sediment as the dominant source of Tl. Much work remains to better understand the controls on Tl processing through a subduction zone. For example, Tl could be retained in residual phengite, offering the potential exploration of Cs/Tl ratios as a slab thermometer. However, data for Tl partitioning in phengite (and other micas) is required before developing this application further. Establishing a database of Tl concentrations and stable isotopes in subduction zone lavas with different thermal parameters and sedimentary inputs is required for the future use of Tl as a subduction zone tracer.