Geochemistry

This study documents the chemical and textural responses of zircon in the Elba igneous complex, with particular reference to the 7-to 7.8-Ma-old Monte Capanne pluton in relation to its coeval volcanic counterpart (Capraia), using BSE imaging and quantitative electron microprobe analyses. The Monte Capanne pluton displays multiple field and geochemical evidence for magma mixing. The samples we have investigated (including monzogranitic, mafic enclave and dyke samples) display similar zircon textures and are associated with an extremely large range of trace and minor element (Hf, Y, HREE, Th, U) compositions, which contrast with relatively simple textures and zoning patterns in zircons from a Capraia dacite. We have used a relatively simple textural classification (patchy zoning, homogenous cores, oscillatory zoning and unzoned zircon) as the basis for discussing the chemical composition and chemical variation within zircons from the Monte Capanne pluton. Based on these data and other works in Lithos 78:101-118, 2004 , it is inferred that mixing between metaluminous and peraluminous melts occurred early in the evolution of the Monte Capanne magma chamber. In particular, mixing was responsible for the development of the patchy-zoning texture in the zircon cores, which was associated with reactions between other accessory phases (including monazite, apatite, allanite), which we infer to have significantly affected the Th distribution in zircon. Zircons from the MC pluton displaying ''homogeneous cores'' have chemical affinities with zircons in the coeval Capraia volcanic system, consistent with the participation of a Capraia-like mantle end-member during mixing. Further zircon growth in the MC pluton produced the oscillatory zoning texture, which records both long-term (crystal fractionation) and transient (recharge with both silicic and mafic magmas) events in a hybrid magma chamber. It is inferred that Hf and the Th/U ratio cannot be used alone to infer magmatic processes due to their dependency on temperature, nor are they a diagnostic feature of xenocrystic grains. This study shows that zircon chemistry coupled with detailed textural analysis can provide a powerful tool to elucidate the complex evolution of a magma system.

The ancient rock city of Petra, which lies south of the Dead Sea in the Hashemite Kingdom of Jordan, displays with its unusual sandstone architecture an abundance of evidence of the Nabatean culture. Petra has gained special recognition for its around 600 hundred of rock facades carved out of the sandstone rock found there. Today, the existence of the unique rock architecture of these monuments is in danger due to the action of flash floods, decomposition, poor maintenance and lack of conservation. Within on-site work and field research in collaboration with the CARCIP (Conservation and Restoration Center in Petra), findings about the process of tafoni-weathering of the cambric sandstone by the interaction of uncontrolled flowing rainwater and salt could be gathered. A new technique for desalination by sprinkling the contaminated areas has been developed and employed. An inventory of risks, damages and needs of around one third of all monuments was done. Special attention was paid to drainage systems, static tension cracks, loose ashlars and rock slabs, rubble and dilapidation. The inspections revealed more than half of all stone facades were equipped with drainage systems. In consequence a maintenance strategy by partly repair and reactivation of the ancient drainage systems and cisterns was developed. Dry slaked lime mortars, according to the still found ancient decoration mortars on the facades were produced in historic technique. The mortar was tested in situ and by salt bursting tests. The hydraulic Ancient cistern mortar was investigated by grain size distribution, binder and aggregate relation and by using electron microprobe analysis (EMPA) to identify the source and type of hydraulic binding material.

In the SW Urals a change of tectonic conditions occurred at around 620 Ma leading to a detrital input from contrasting provenance areas. Fifty-seven detrital zircons were separated from Proterozoic sandstones of this setting to study their typologies and pattern of U-Pb systematics.

Dispersed quartz veinlets in Proterozoic enderbitic charnockite from Tromøy, Bamble sector (southern Norway), with Ti-concentrations of mostly 80–180 ppm, produce bright blue cathodoluminescence (CL), against contrasting micro-textures of secondary pure quartz with low CL intensity. The textures comprise grain boundary alteration, healed micro-fractures, patches of secondary quartz, and euhedral quartz nuclei. The secondary quartz locally makes up 50% of the total quartz. Trace element analysis has been done by electron-probe micro-analysis (EPMA), laser-induced coupled plasma mass spectrometry (LA-ICPMS), and additional electron-paramagnetic resonance (EPR) spectroscopy. These studies testify systematic trace element reduction and extensive quartz recovery during retrograde metamorphism. We assume healing of a part of the aqueous fluid inclusions during a late thermal event, possible correlated with Paleozoic magmatic activity in the Oslo-Rift. During final cooling, aqueous fluids were largely retrapped in patches of secondary quartz associated with healed fractures, whereas carbonic inclusions (without secondary quartz) may have survived retrograde metamorphism. The variable but generally high salinity of fluid inclusions is assumed to be in part the result of quartz recovery by which ion concentrations were increased in the percentage range.

We present electron microprobe, secondary ion mass spectrometry, and laser ablation inductively coupled mass spectrometry data for common trace elements (Li, Al, Ti, Na, K, Fe) in quartz. Our samples from both magmatic and hydrothermal environments all show heterogeneity at the single grain scale.