Isotope Geology and Petrology
Isotope Geology
Isotope geology interprets isotopic signals to reconstruct geologic processes. These signals result from the physical and chemical separation of isotopes and from radioactive processes. Radiometric dating allows to assign an absolute age to geologic processes. This method is based on the radioactive decay of a parent isotope to a daughter isotope using the half-life (time interval after which half of the initial amount of the parent isotope has decayed) to calculate an age. Depending on the geologic setting the rock originates from, the rock´s mineral content, and the isotopic system selected for analysis the temporal succession of important geological events can be reconstructed. These events could be, for example, magmatic or metamorphic crystallization, erosion and cooling of rocks, volcanic eruptions, or deposition and diagenesis of sediments.
Current research by our group focusses on understanding the development of magmatic systems. We study minerals that are stable even at magmatic temperatures and that contain the radioactive element uranium (U) such as zircon, allanite, baddeleyite, or monazite. Some of the decay products of U are short-lived (e.g., 230Th) and others are stable (e.g., Pb and He). Using the ion probe (SIMS = secondary ion mass spectrometry) is essential to determine the duration of crystal growth over natural time scales. The isotopic fingerprint of the minerals makes it possible to resolve their origin in a geological and archaeological context, for example when dating and correlating volcanic deposits.
Petrology
Rocks are archives of the geologic history of the Earth as well as witnesses of hidden processes occurring deep in the Earth which are crucial for the development of the planet. The composition, texture, and structure of rocks helps to decipher their origin in respect of the physical and chemical conditions during their formation. Geological processes such as magmatism, weathering, diagenesis, or metamorphism leave traces in the mineral components whose isotopic composition can vary in the micro- to nano-range. Therefore, petrologic research applies a variety of microscopic methods (from the petrographic microscope to the ion probe) which are available in a unique constellation at the Institute of Earth Sciences Heidelberg.
News
Anne Sturm was awarded the “Student Poster Award” at the yearly meeting of the section “Geochemistry/Petrology & Petrophysics” of the German Mineralogical Society (DMG) in Mainz (2022). Congrats, Anne!
She received the award for her contribution “Permian magmatism and a billion years of crustal evolution below the Eifel, Germany: Deep insights from crustal xenoliths and zircon”. Anne is doing a PhD in our research group.
Blue glasses from lime kilns was used in Baroque architecture to substitute expensive lapis lazuli. The causes of their color, however, remained unknown. Electron microscopy has now resolved this enigma using a sample collected by Goethe during his Italian travels. [Read the paper (in German)]
Supervolcanoes remain active and dangerous even thousands of years after their eruption - this is what an international team of researchers including Prof. Dr. Axel Schmitt from the Institute of Earth Sciences at Heidelberg University found in their study on Toba volcano which erupted on the island of Sumatra (Indonesia) arounf 75.000 years ago. [Press release]
Title of the PhD thesis: "Eruptive recurrence and magma accumulation for Quaternary stratovolcanoes in Central Anatolia"
Paul-Ramdohr-Award to Bjarne Friedrichs
Bjarne Friedrichs received the Paul-Ramdohr-Award for 2020. This award of the German Mineralogical Society (DMG) is presented to the two best contributions by early career scientists.
Way to go!
Title of the PhD thesis: "Magmatic processes and timescales of explosive volcanoes of the Chiapanecan and Central American volcanic arcs through zircon petrochronology"
Maya blue is a pigment of the Maya which was prepared from special clays and Indigo. How these clays formed was so far unknown. Alejandro Cisneros and a group of Heidelberg students could demonstrate that these clays formed from volcanic ash which erupted from 40–50 million year old volcanoes. [More]
...could show on the reverse a volcano in present-day Turkey. Did this volcano erupt during Roman times, as some believe? Find out more about Bjarne Friedrich’s research here.
Blue zircon is extremely rare in nature. Heating can give naturally brown-red zircon a blue color, and these crystals are praised as gemstones. Yi Sun has now discovered the cause for the natural blue color in zircon from Vesuvius. [Read publication]
Talk by Prof. Olivier Bachmann, currently visiting professor in the research group "Isotope Geology and Petrology"
Title: "Dynamics of transcrustal magmatic systems, and their consequences on volcanic behaviour"
When: Fri, 22.03.19, 11:15am
Where: INF236 R516
Poster award for Bjarne Friedrichs at GeoBonn 2018 (Annual meeting of DGGV, DMG and PalGes) for his poster "Holocene Silicic Volcanism at Mt. Erciyes, Central Anatolia, Turkey“
Acquisition under way of a new correlative Raman and scanning electron microscope (RISE by ZEISS and WITec)
Members of the research group on the summit of Hasan Dagi (3253 m) in order to sample for the DFG Project „Eruptive recurrence and magma accumulation for Quaternary stratovolcanoes in Central Anatolia“
New study on the evolution of Toba caldera after the supereruption in cooperation with researchers from the US, Australia, and Indonesia
https://www.nature.com/articles/ncomms15248
Image courtesy of NASA/GSFC/MITI/ERSDAC/JAROS, and the U.S./Japan ASTER Science Team.
Presentation of HIP - Heidelberg Ion Probe during the RIMG Shortcourse (Vienna 2017)
http://vienna2017.petrochronology.org/program/
Publication & cover photo in the journal "Geology":
Tierney, C. R.*, Schmitt, A. K., Lovera, O. M., & de Silva, S. L. (2016). Voluminous plutonism during volcanic quiescence revealed by thermochemical modeling of zircon. Geology, 44(8), 683-686.
Student field trip to Oman:
In March a small group of geology students and professors from Heidelberg went to Oman to study the petrology of the oceanic crust and learn about geochemical and tectonic processes of the Oman-Ophiolith. The ophiolith represents a complete sequence of oceanic crust and upper mantle which is usually located in several kilometers of depth and under a few kilometers of water, well hidden from the researchers' eyes. In the Oman mountains this sequence comes up to surface and offers the rare opportunity to investigate several million year old oceanic rocks at the Earth's surface.
2015 Gondwana Research Best Paper Award for
Robinson, Paul T., Robert B. Trumbull, Axel Schmitt, Jing-Sui Yang, Jian-Wei Li, Mei-Fu Zhou, Jörg Erzinger, Sarah Dare, and Fahui Xiong. "The origin and significance of crustal minerals in ophiolitic chromitites and peridotites." Gondwana Research 27, no. 2 (2015): 486-506.
The paper reports the surprising presence of crustal minerals in oceanic upper mantle rocks from Tibet, Oman and Russia.
Is there a strombolian eruption (photo) depicted in a 35000 year old cave painting in south-eastern France? This is what French scientists assume who dated samples of volcanic rocks from the Bas-Vivarais Region at approximately this age. In an interview with the journal NATURE Axel Schmitt from the Institute of Earth Sciences at Heidelberg University commented on the results.
Photo: Stromboli (Felix Wicke)
Publication of the Master student Wan-Ning-Wu „U-Th baddeleyite geochronology and its significance to date the emplacement of silica undersaturated magmas” presented as “Highlight and Breakthrough“ in the October edition of the journal „American Mineralogist“ (Bernal, J. P., 2015, Reaching new boundaries for in-situ U-Th geochronology. American Mineralogist, 100[10], 2017-2017).
