Projects

High-Precision Geochronology

• Deformation processes along major continental transforms
• Strain accumulation and reoccurrence of paleoseismic events
• The role of fluids in active fault zones
• Dating of primary and secondary carbonates
• Calibration of absolute time in Earth’s history using sedimentary archives
• Resolving magmatic processes
• Resolving processes in ore deposits
• Quantifying absolute time in the evolution of early terrestrial life

Isotopic Tracing

• Petrogenesis of magmatic rocks from different geodynamic settings
• Metallogenetic processes
• Tracing sources of fluids in ore deposits
• Paleoenvironmental changes
• Anthropogenic processes

Petrochronology, Thermochronology, and ⁴⁰Ar/³⁹Ar Geochronology

• Quantify thermal and exhumation histories using U/Pb, ⁴⁰Ar/³⁹Ar, and fission track methods for tectonic analysis
• Directly measure the timing of deformation and fluid interactions
• Determine the age and preservation potential of ore-forming systems
• Assess mechanisms driving daughter isotope loss in natural systems
• Develop thermochronometers for temperatures exceeding 300°C

Deformation processes along major continental transforms (Perach Nuriel) Continental transform plate boundaries are some of the most tectonically active structures on earth, producing relatively shallow and high-magnitude earthquakes within densely populated areas. We are interested to better understand the evolution and activity history of these structures from initiation to present day activity pattern. Previous projects in the Dead Sea Transform and the Eastern California Shear Zone demonstrated the reactivation behavior and the non-uniform activity pattern of these long-lived structures. Current projects are focused on the North Anatolian Fault Zone.
	Strain accumulation and reoccurrences of paleoseismic events (Perach Nuriel) The general concept of “earthquake cycle” is based on limited paleoseismological archives from the past 20,000. These records are essential for our understanding of faults behavior and the seismic cycle. In recent years, studies of crack-seal veins provided important information on their growth mechanisms, demonstrating their periodicity and potential to preserve the seismic cycle (both seismic and a-seismic periods). Our group advocate for the use of crack-seal type veins as potential archives for studying deformation rates, reoccurrences of events, and for temporally constraining the seismic cycle and we currently apply this method along the active North Anatolian Fault Zone.
The role of fluids in active fault zones (Perach Nuriel) Various roles and mechanisms have been proposed for fluids in fault zone including, earthquake-mobilized fluids; fault-valve behavior, fluid-enhanced healing, passive advective of meteoric water, local pressurized solutions; or a combination of several mechanisms. Many of these studies are based on geochemical-isotopic analyses of secondary precipitates from fault zones. Combined with high-resolution dating we could demonstrate the progressive evolution of fluids during the seismic cycle and during fault-life history. We are therefore committed to improving temporal resolution and accuracy to study fluids behavior in active fault zones.
	Dating of primary and secondary carbonates (Perach Nuriel, Maria Ovtcharova) Our group has experience with dating of various types of carbonate material including secondary carbonates such as nodules, microcodiumsm, cements, oncoids, speleothems, and stromatolites. We have also successfully dated primary dolomite and limestone units from the Archean time to the Pliocene. Following a textural study of the sample we mechanically separate several sub-samples from small microstructures using microdrilling device. Following a column-chemistry separation in clean-lab environment, the U-Pb or U-Th isotopes of several sub-samples are used to construct a Terra-Wasserburg or U-Th isochron ages, respectively. We are interested in working with new material and potentially other minerals with low-uranium content.
Calibration of absolute time in Earth’s history using sedimentary archives (Maria Ovtcharova) The quantification of the Geological time scale relies on detailed and accurate geochronology. We contribute to a series of research projects using high precision U-Pb geochronology of zircon in volcanic ash beds interlayered with sedimentary strata. This technique was applied to Ediacaran-Cambrian boundary (Linnemann et al., 2018); calibration of late Carboniferous (Pointon et al., 2012); lower and middle Triassic (Ovtcharova et al., 2006; Galfetti et al., 2007) and Paleocene-Eocene thermal maximum (in progress). This research was combined with developing strategies for the accurate definition of geological boundaries in complex sedimentary sections and developing a probabilistic approach for accurate interpretation of complex geochronological U-Pb results (Ovtcharova et al., 2015).
	Resolving magmatic processes: differentiation, duration, crystallization and cooling history (Maria Ovtcharova, Thoriso Lekoetje) The recent research in the field of magmatic petrology brings evidence that plutons are incrementally assembled by repeated magma injections and eventually build up huge complexes over extended periods of time. Timescales of pluton construction may vary from 104 to 106 years (in most Phanerozoic igneous complexes) to 108 years (in massif Anorthosites of the Proterozoic). Using high precision, chemical abrasion, isotope dilution thermal ionization mass spectrometry (CA-ID-TIMS) U-Pb zircon geochronology and high precision U-Pb on baddeleyites it is possible to resolve individual magma pulses and to track both the thermal and crystallization histories of magmatic systems at high temporal resolution. Examples of this approach are the results of our work in the Rustenburg Layered Suite (RLS) of the Bushveld Complex, which represents Earth’s oldest large igneous province crystalised in < 1 Ma (Zeh et al., 2015) and our current research on Kunene Anorthosite Complex in Angola and Namibia.
Resolving processes in ore deposits (duration and mechanism of ore formation) (Maria Ovtcharova) The timing of magmatism also has tremendous implications for the style and timescales of magmatic-hydrothermal ore deposits (Chiaradia et al., 2013). In order to provide the temporal link between magmatism and ore formation we apply high precision U-Pb dating of various magmatic (zircon, titanite, rutile) and some hydrothermal minerals (apatite, titanite, monazite, xenotime, rutile) and combine this with element chemical analyses both in-situ before, and in solution after dissolution of the dated minerals, as well as Hf isotope analysis. A major analytical problem to overcome is the partial loss of radiogenic Pb in zircon, which is related to the hydrothermal fluids that are in contact with the grain. In addition, precision of U-Pb dates in igneous zircon associated with ore deposits gets compromised by the presence of melt inclusions and elevated common Pb in the zircon lattice, which results in low radiogenic to common lead ratios. Nevertheless, the results obtained in our lab for several projects of the Ore deposit group in Geneva (mainly for ore deposits in Peru), in combination with a wealth of other geochronological, chemical and petrological analyses brought interesting outcomes (Chelle-Michou et al., 2014; Catchpole et al., 2015; Kouzmanov et al., 2008).
	Quantify absolute time in the evolution of early terrestrial life (Maria Ovtcharova) The 4.5-billion-year long Earth history has passed several milestones. One of them, at approximately 540 Ma, was the so called “Cambrian explosion” – an eruption of complex life recorded in fossils from around the world. This huge evolutionary jump from simple to more complex life forms happened after one unique first experiment – the late Neoproterozoic Ediacaran biota, which similarly to the Cambrian explosion started with rapid diversification but then declined and faded away, giving place to the more successful Cambrian metazoans. Whether Ediacaran-type biota gradually evolved into Cambrian biota, disappeared after a long decline or became rapidly extinct due to external, environmentally driven forces in the Early Cambrian remains the subject of debate. We aim to establish a more robust timescale for the evolution of Ediacaran biota as a function of time and paleo-latitude and to link their evolution to environmental changes. The research is carried out in several Ediacaran sections in Namibia, Ukraine, Ural and linked to a international GRIND drilling project via collaboration with Ulf Linnemann from Senckenberg Museum, Dresden (Linnemann et al., 2018; Soldatenko et al., 2019).
Petrogenesis of magmatic rocks from different geodynamic settings (Massimo Chiaradia, Hugo Carrasco Ronquillo, Wen-jie Xia) Analysis of whole rocks and mineral separates. Applications: petrogenesis of magmas from various geodynamic settings.
	Metallogenetic processes (Massimo Chiaradia, Hugo Carrasco Ronquillo) Mineral analysis (silicates, sulphides, sulphates, phosphates, oxides, carbonates). Applications: trace magmatic and hydrothermal ore-forming processes.
Trace sources of fluids in ore deposits (Massimo Chiaradia, Hugo Carrasco Ronquillo) Fluid analysis (fluid inclusions in minerals through the crush-leach technique, volcanic gases, organic fluids, waters). Applications: trace sources of fluids in ore deposits, behavior of metals during volcanic degassing.
	Paleoenvironmental changes (Massimo Chiaradia) Fossil analysis (carbonate and apatite down to sub-mg amounts). Applications: indirect dating of marine rocks (Sr isotope chronostratigraphic method) and tracing pre-historic human migrations.
Anthropogenic processes (Massimo Chiaradia) Modern and ancient handcraft analysis. Applications: forensic and archeometric studies.
	Measure the thermal and exhumation histories of minerals and rocks using the U/Pb, 40Ar/39Ar (in-situ and furnace heating) and fission track methods: Tectonic Analysis (Richard Spikings, Vidar Jakobsson) The reconstruction of continuous thermal histories is a powerful tool to address numerous questions in earth Sciences, ranging from investigating academic themes such as i) crustal thickening and orogenesis, ii) continental rifts, iii) cratonic stability, to questions that also have a commercial interest, including i) basin analysis, and ii) metallogenesis, telescoping and the preservation potential of mineralised regions. Careful consideration is placed on the potential for fluid interaction to reset isotopic reservoirs in minerals, which can invalidate the numerous assumptions that form the basis of thermochronology. Recent projects in our laboratory include studies from Venezuela, Colombia, Ecuador, Chile, Antarctica and the USA.
Directly measure the timing of deformation and fluid interaction (Richard Spikings, Vidar Jakobsson) In-situ 40Ar/39Ar and U-Pb isotopic measurements of common minerals such as potassium feldspar and micas, and accessory minerals such as apatite are combined with petrological characterisation of single crystals (e.g. using back-scatter electron, EPMA, stable isotope compositions) to investigate the dominant mechanisms that modify isotopic reservoirs. The in-situ dates are frequently compared with in-situ measurements of Rb-Sr dates. Such characterisation is important in thermochronology because it tests the fundamental assumption that daughter isotopes are solely lost by volume diffusion, and thus the accuracy of the thermal history solutions. These data also improve the accuracy of measurements of the timing of deformation and fluid flow events. Our laboratory has focused on Triassic granodiorites taken from the Andes of Colombia and Ecuador, Precambrian meta-igneous rocks of Madagascar, and Precambrian metasedimentary rocks, granites and pegmatites from the Black Hills, USA.
	Determine the age and preservation potential of ore forming systems (Richard Spikings, Hugo Carrasco Ronquillo) Our 40Ar/39Ar laboratory is frequently used to date mineral deposits, by analysing the Ar isotopic compositions of minerals such as adularia, alunite and hydrothermal micas. These are usually used as proxies for the timing of fluid flow, and dates with absolute precisions better than ±50 Ka (i.e. better than approximately ±0.3% for Miocene deposits) can be used to date discrete phases of circulation of mineralising fluids, building more accurate models of how ore deposits form. Recent projects in our laboratory include studies in Ecuador, Peru, Armenia, Bulgaria and Turkey.
Assess the mechanisms that drive daughter isotope loss in natural systems (Richard Spikings, Vidar Jakobsson) In-situ 40Ar/39Ar and U-Pb isotopic measurements of common minerals such as potassium feldspar and micas, and accessory minerals such as apatite are combined with petrological characterisation of single crystals (e.g. using back-scatter electron, EPMA, stable isotope compositions) to investigate the dominant mechanisms that modify isotopic reservoirs. The in-situ dates are frequently compared with in-situ measurements of Rb-Sr dates. Such characterisation is important in thermochronology because it tests the fundamental assumption that daughter isotopes are solely lost by volume diffusion, and thus the accuracy of the thermal history solutions. These data also improve the accuracy of measurements of the timing of deformation and fluid flow events. Our laboratory has focused on Triassic granodiorites taken from the Andes of Colombia and Ecuador, Precambrian meta-igneous rocks of Madagascar, and Precambrian metasedimentary rocks, granites and pegmatites from the Black Hills, USA.
	Development of thermochronometers at temperatures higher than 300°C. (Richard Spikings, Vidar Jakobsson) A majority of thermochronological analyses since the 1970’s were made using fission track and (U-)/He systems, and thus are sensitive to temperature lower than approximately 300°C. Several PhD projects have tested the utility of the U-Pb (apatite), 40Ar/39Ar (potassium feldspar, muscovite) methods to derive thermal history solutions, by testing the assumption that i) daughter isotopes were only lost by thermally driven diffusion, and ii) laboratory diffusion experiments that last from minutes to weeks, mimic diffusion at lower temperatures over geological timescales.