different steps of the metamorphic evolution. Rutile grains that equilibrated their Zr concentrations at temperatures above 1070 °C (i.e. 1.1 wt% Zr) could not retain all Zr in the rutile structure during cooling and exsolved baddeleyite (ZrO 2 ). By subsequent reaction of baddeleyite exsolution lamellae with SiO 2 , zircon needles formed before the system finally closed at 650-700 °C without significant net loss of Zr from the whole host rutile grain. By reintegration of zircon exsolution needles, peak metamorphic temperatures of up to 1190 °C are derived for the studied rocks, which demonstrates the suitability of this solution thermometer to record UHT conditions and also confirms the extraordinary geological setting of the lowermost part of the Ivrea Zone.

Chondrules from unequilibrated ordinary and carbonaceous chondrites belong to the oldest and most primitive materials from the early solar system and record chemical and isotopic signatures relating to their formation and evolution. These signatures allow tracing protoplanetary disk processes that eventually led to the formation of planetary building blocks and rocky planets. 26 Al-26 Mg ages based on mineral-mesostasis isochrons of 31 porphyritic ferromagnesian chondrules, that belong mainly to type-II, constrain the time of chondrule melting prior to incorporation into the respective chondrite parent bodies. For this study chondrules from the unequilibrated L, L(LL) and LL ordinary chondrites (UOCs) NWA 5206, NWA 8276, MET 96503, MET 00452, MET 00526, NWA 7936 and QUE 97008 were selected, which are of petrologic types 3.00 to 3.15 and were thus least metamorphosed after formation. Magnesium and Al isotopes were measured in-situ by Secondary Ion Mass Spectrometry (SIMS) using a CAMECA 1280 ims. 26 Mg excess from in-situ decay of 26 Al correlating with 27 Al/ 24 Mg has been detected in the mesostasis of all but one chondrule. The initial Al isotopic compositions (26 Al/ 27 Al)0 and 26 Mg/ 24 Mg ratios (d 26 Mg*0) deduced from internal mineral isochron regressions range from (9.5 ± 2.8) × 10-6 to (3.1 ± 1.2) × 10-6 and-0.020 ± 0.028‰ to 0.011 ± 0.039‰, respectively. The corresponding chondrule ages (∆tCAI), calculated relative to calcium-aluminum-rich inclusions (CAIs) using the canonical 26 Al/ 27 Al = (5.23 ± 0.13) × 10-5 , are between 1.76 %&.'()&.*+ and 2.92 %&.*.)&./0 Ma and date melt formation and thus the primary chondrule formation from dust-like precursors or reprocessing of older chondrules. The age range agrees with those acquired with different short-lived chronometers and with published 26 Al-26 Mg ages, the majority of which were obtained for chondrules from the Bishunpur and Semarkona meteorites, although no chondrule with (26 Al/ 27 Al)0 > 10-5 was found. Chondrules in single chondrite samples or between different chondrite groups show no distinct age distributions. The initial 26 Al/ 27 Al of the oldest chondrules in the L(LL)/LL and L chondrite samples are identical within their 1σ uncertainties and yield a mean age of 1.99 %&.&1)&.&1 Ma and 1.81 %&.0&)&.00 Ma, respectively. The oldest chondrules from six of the seven studied samples record a mean age of 1.94 %&.&+)&.&(Ma. Since heating events in the protoplanetary disk could have partially reset the Al-Mg systematics in pre-existing chondrules and this would have shifted recorded 26 Al-26 Mg ages toward younger dates, the oldest mean age of 1.81 %&.0&)&.00 Ma recorded in L chondrite chondrules is interpreted to date the rapid and punctuated onset of chondrule formation. The density distribution of chondrule ages from this study, which '. 12 %&.**

Dendrometers offer a useful tool for long-term, high-resolution monitoring of tree responses to environmental fluctuations and climate change. Here, we analyze a 4-year dendrometer dataset (2014-17) on European beech (Fagus sylvatica L.), common hornbeam (Carpinus betulus L.) and pedunculate oak (Quercus robur L.), co-occuring in a mixed broadleaved forest in northeastern Germany. In our analyses, we focus both on seasonal growth dynamics as well as on the environmental forcing of daily stem-size variations. Over the study period with contrasting weather conditions, we observed species- and year-specific differences in growth phenology (i.e., growth onset, cessation and duration). Oak was characterized by early growth onset and long growth duration in all years as compared with beech and hornbeam. The analysis on the environmental forcing of daily stem dynamics revealed, however, highly similar responses for the studied species, with current-day vapor pressure deficit and sunshine duration negatively, and relative humidity and precipitation positively affecting stem size. When considering lagged effects, environmental conditions often oppositely affected stem-size changes. No consistent seasonality in environmental responses was detected, though specific weather conditions were found to affect temporal patterns in individual years. We suggest that the high similarity in environmental forcing observed between tree species can be explained by daily stem-size changes mainly reflecting tree water status rather than tree growth. Our results stress that correcting dendrometer series for reversible stem hydrological changes is of utmost importance to better quantify tree growth from dendrometers in future.

A new natural rutile reference material is presented, suitable for U‐Pb dating and Zr‐in‐rutile thermometry by microbeam methods. U‐Pb dating of rutile R632 using laser ablation ICP‐MS with both magnetic sector field and quadrupole instruments as well as isotope dilution‐thermal ionisation mass spectrometry yielded a concordia age of 496 ± 2 Ma. The high U content (> 300 μg g−1) enabled measurement of high‐precision U‐Pb ages despite its young age. The sample was found to have a Zr content of 4294 ± 196 μg g−1, which makes it an excellent complementary reference material for Zr‐in‐rutile thermometry. Individual rutile grains have homogeneous compositions of a number of other trace elements including V, Cr, Fe, Nb, Mo, Sn, Sb, Hf, Ta and W. This newly characterised material significantly expands the range of available rutile reference materials relevant for age and temperature determinations.

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