22Rutile is an important mineral host for high-field strength elements, so its solubility in 23 geologic fluids at high pressure and temperature plays an important role in the crustal and mantle 24 processes that control the terrestrial cycling of these elements. However, experimental 25 measurements of rutile solubility are in conflict by a factor of more than 100 at most studied 26 conditions. We performed new measurements of rutile solubility in H 2 O-albite and H 2 O-27 Na 2 Si 3 O 7 (NS3) fluids by in-situ synchrotron-radiation X-ray fluorescence spectroscopy using 28 modified Bassett-type hydrothermal diamond-anvil cells. Minimum detection limits were 1.9 and 29 2.3 ppm Ti by weight for the two cells. Three albite-H 2 O experiments at starting bulk 30 compositions of 2.7, 6.7 and 10.3 wt% albite involved spectral acquisition at rutile saturation in 31 the presence of albite crystals, melt, or a single homogeneous fluid phase; after accounting for 32 the additional phases, corrected fluid compositions were 0.6 to 7.5 wt% dissolved silicate over 33 the run conditions. At ≤2.7 wt% albite, rutile dissolution rate was slow and steady state was not 34 achieved at 600-800 °C; however, at higher dissolved albite contents, constant solubility with 35 time was observed. Rutile solubilities in the presence of a single fluid phase at 700 °C, 0.79 GPa, 36 5.4 wt% albite, and at 800 °C, 1.10 GPa, 6.7 wt% albite, were 37±2 and 156±6 ppm, 37 respectively. These data agree with results acquired using hydrothermal piston-cylinder methods 38 with long run times and suppression of new crystal growth, but not with data derived from visual 39 observation in hydrothermal diamond-anvil cells. This discrepancy is likely due to lack of 40 equilibrium in the latter approach. Two experiments in 10 and 30 wt% NS3 at 660-800 °C, 41 0.5±0.1 GPa, show extreme concentration-dependent rutile solubility enhancement to ~4500 42 ppm. The data indicate a strong positive correlation between rutile solubility and Na/Al. Because 43 (Na+K)/Al is likely to be greater than unity in aqueous fluids at high pressure and temperature 44 3 due to incongruent dissolution of albite and micas, the increase in rutile solubility along the 45 albite-NS3 join points to the possibility of significant Ti transport by silicate-bearing aqueous 46 fluids in the lower crust and upper mantle. 47 48

The ESRF synchrotron beamline ID22, dedicated to hard X-ray microanalysis and consisting of the combination of X-ray fluorescence, X-ray absorption spectroscopy, diffraction and 2D/3D X-ray imaging techniques, is one of the most versatile instruments in hard X-ray microscopy science. This paper describes the present beamline characteristics, recent technical developments, as well as a few scientific examples from recent years of the beamline operation. The upgrade plans to adapt the beamline to the growing needs of the user community are briefly discussed.

Seasonality is encoded in palaeoproxies of secondary cave mineral deposits (speleothems) and the code is becoming cracked. The petrology of calcite stalagmites from Obir, an Alpine (1100 m altitude), perennially wet cave, was characterized by optical and electron backscatter diffraction, and their chemistry by bulk ICP-MS analysis, ion microprobe and synchrotron-based micro-X-ray fluorescence. Vadose water penetrates 70 m through Triassic limestones (with some Pb–Zn mineralization) to the chamber Säulenhalle where the stalagmites were collected. Strong seasonal ventilation in the cave leads to low PCO2 in winter associated with falls in speleothem sulphate S and increase in δ13C values. All samples display autumnal event lamination defined by a narrow, optically visible zone with increases in trace element concentrations, within which synchrotron studies have resolved μm-scale enrichments of Pb and Zn. Small-scale (10 µm) lateral trace element variations reflect alternate flat faces and rough crystal edges, influenced by high Zn content. The elemental covariations are consistent with the transport of Pb, Zn, P, F, Br and I adsorbed onto organic colloids in dripwater, but the final deposition may have been from aerosols and we propose this as a new mechanism requiring further investigation. This study represents the most complete demonstration of how chemical variations are powerful expressions of seasonal cave physiology in humid temperate caves, including the contrast between summer and winter conditions, and the preservation of sub-weekly events during the autumn season.

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