AG Petrology of the Ocean Crust

Room 5350

Department of Geosciences
University of Bremen
Klagenfurter Straße 2
28359 Bremen
Germany

Phone: +49 421 218 65404
Fax: +49 421 218 65429
Email: diehl@uni-bremen.de

Alexander Diehl


Dissertation

Energetic and chemical dynamics of mid-ocean ridge and island arc associated hydrothermal systems

The project “Magma hydrothermal interactions in island arcs” aims to assess the coupled energetic and chemical mass transport processes in the magmatic-hydrothermal interface of island arcs. Besides analyses of phase assemblages in volcanic rocks and hydrothermal precipitates, investigations on fluids and volatiles expelled at vent sites are performed. The solid material is used for a thermobarometric approach using phase transitions in fluid inclusions to reconstruct the physical conditions, to consider stable isotope (Sr, O) geochemical mass balances. The work program is complemented by selected geophysical observations directly related to the interplay of magmatic and hydrothermal processes. The overarching aim includes the classification of island arcs regarding their energetic and chemical properties and the evaluation of the role of magma-hydrothermal processes in the long-term evolution of the system earth. The new findings will be essential in understanding the energetic and chemical evolution of the ocean and the oceanic lithosphere and also set a basis for further interdisciplinary approaches. Beside metallogenetic processes and potential deep-sea mining endeavors, the hydrothermal activity is directly related to microbial communities occurring in the water column as it can provide important micronutrients to their habitats.



Agenda

Hydrothermal systems in the Kermadec island arc

  • Recovery of and investigations on hydrothermal fluids, precipitates and volcanic rocks from remote sensing explored volcanic edifices.
  • Performance of combined fluid and rock analysis for energetic and geochemical mass balance calculations to examine the energetic and chemical mass transport between the sampled magmatic and hydrothermal systems.


Hydrothermal systems associated with the ultra-slow spreading Gakkel Ridge

  • Sampling of hydrothermal vent sites and hydrothermally influenced sediments near vent sites.
  • Microthermometric investigations on hydrothermal precipitates potentially occurring at the Karasik Seamount to assess the development of hydrothermal systems at ultra slow spreading ridges.
  • Transfer of thermobarometric results and geophysical measurements to a numerical geothermal model.


Geothermal modeling of the oceanic lithosphere

  • Development of a numerical approach to estimate the general lithospheric temperatures and considerations on regional scenarios with magmatic and hydrothermal influences.
  • Calculation of hydrothermal energy uptake and estimation of fluid mass transport in hydrothermal environments.
  • Global predictions on the hydrothermal contribution to the overall lithospheric energy loss.


Methods

  • Recovery of volcanic rocks and hydrothermal precipitates (ROV-grab, box corer).
  • Recovery of escaping fluids from chimneys or orifices at vent sites (ROV-IGT).
  • Sampling, processing and analysis of fluids from hydrothermal plumes (GC).
  • Gravity coring of hydrothermally influenced sediments.
  • Microscopic investigations on volcanic rocks and hydrothermal mineral assemblages coupled to additional analytics (LA-ICPMS, ESM).
  • Micro thermometric investigations on phase transitions of fluid inclusions in hydrothermal minerals.
  • Analysis of strontium- and oxygen isotope systems (TIMS) and use of the results for geochemical mass balance calculations.
  • Numerical modeling of complex geothermal scenarios under consideration of chosen geophysical evidences.
  • Reaction path modeling using thermal and geochemical data.



Expeditions

Cruise participations

  • 31.05.2018 - 28.06.2018: SO263: Northern Tonga Arc; Suva (Fidji) - Suva (Fidji)
  • 22.12.2016 - 21.01.2017: SO253: Kermadec Arc; Nouméa (New Caledonia) - Auckland (New Zealand)
  • 09.09.2016 - 23.10.2016: PS101 / ARK XXX-3: Karasik seamount (Gakkel Ridge, Arctic Ocean) at 86°N 60°E; Tromsø (Norway) - Bremerhaven
  • 09.02.2015 - 23.02.2015: Field work in the Oman Ophiolite Complex
  • 05.07.2014 - 03.08.2014: PS86 / ARK XXIII-3: Aurora sea mount in the Arctic Ocean at 82°N, 6°W; Tromsø (Norway) - Tromsø



Scientific career

  • 2009 - 2012: B.Sc. Geosciences at Bremen University
    • 2012: Bachelor thesis: "Geochemische Untersuchungen an hydrothermalen Bildungen aus dem Arnsteinvulkan,Ostsauerland - Rekonstruktion des Temperaturmilieus anhand einer mikrothermometrischen Studie und einer Sauerstoffisotopenanalyse"
  • 2012 - 2015: M.Sc. Geoscience at Bremen University
    • 2015: Master thesis: "Formation temperatures of epidote veins in the Wadi Gideah section, Oman Ophiolite: Constraints on cooling of the ocean crust"
  • 2015 - present: Ph.D. student at the research group "Petrology of the Ocean Crust" at Bremen University.



Publications

  • Bieseler B, Diehl A, Jöns N, Lucassen F, Bach W (accepted): Constraints on cooling of the lower ocean crust from epidote veins in the Wadi Gideah section, Oman Ophiolite. Geochemistry, Geophysics, Geosystems
    | doi:10.1029/2018GC007679 |
  • Walter M, Albers E, Bäger J, Diehl A, German C, Hand KP, Horn M, Köhler J, McDermott J, Molari M, Steinmacher B, Wegener G, Wischnewski L, Mertens C, Sültenfuß J, Hoppmann M, Damm E, Bach W, Seewald J (2017): Physical oceanography and biogeochemistry of hydrothermal plumes, in: Boetius A, Purser A (eds.) The expedition PS101 of the Research Vessel POLARSTERN to the Arctic Ocean in 2016. Reports on Polar and Marine Research 706, 63–80.
    | doi:10.2312/BzPM_0706_2017 |
  • Diehl A, Albers E, German CR, Hand KP, Bach W (2017): Geology and hard rock petrology, in: Boetius A, Purser A (eds.) The expedition PS101 of the Research Vessel POLARSTERN to the Arctic Ocean in 2016. Reports on Polar and Marine Research 706, 41–50.
    | doi:10.2312/BzPM_0706_2017 |
  • Dziadek R, Gohl K, Diehl A, Kaul N (2017): Geothermal heat flux in the Amundsen Sea sector of West Antarctica: New insights from temperature measurements, depth to the bottom of the magnetic source estimation, and thermal modeling. Geochemistry, Geophysics, Geosystems 18(7), 2657-2672.
    doi:10.1002/2016GC006755 |
  • Longpre MA, Klügel A, Diehl A, Stix J (2014): Mixing in mantle magma reservoirs prior to and during the 2011-2012 eruption at El Hierro, Canary Islands. Geology 42(4), 315-318.
    doi:10.1130/G35165.1 |



Conference Abstracts

  • Diehl A, Kleint C, Bach W, Strauss H, de Ronde C, Koschinsky A (2017): Contrasting styles of hydrothermal activity in the Southern Kermadec Arc. GeoBremen 2017, Bremen, Germany (Poster).
  • Bieseler B, Diehl A, Jöns N, Bach W (2017): Constraints on cooling of the lower ocean crust from epidote veins in the Wadi Gideah section, Oman Ophiolite. GeoBremen 2017, Bremen, Germany (Poster).
  • McDermott J, Albers E, Bach W, Diehl A, German C, Hand K, Koehler J, Seewald J, Walter M, Wegener G, Wischnewski L (2017): Geochemistry, physics, and dispersion of a Gakkel Ridge hydrothermal plume, 87°N, 55°30’E. Goldschmidt Conference 2017, Paris, France (Poster).
  • Marcon Y, Purser A, Diehl A, Albers E, Türke A, McDermott J, German C, Hand K, Schlindwein V, Dorschel B, Wegener G, Boetius A, Bach W (2017): Geological settings of hydrothermal vents at 6°15’W and 55°30’E on the Gakkel Ridge, Arctic Ocean. Goldschmidt Conference 2017, Paris, France (Poster).
  • Türke A, Bach W, Boetius A, Diehl A, German C, Köhler J, Mertens C, Monien P, Prause S, Sueltenfuss J (2017): Dissolved-particulate exchange in the proximal hydrothermal plume at the Aurora Vent Field, Gakkel Ridge, Arctic Ocean. Goldschmidt Conference 2017, Paris, France (Poster).
  • Bieseler B, Diehl A, Jöns N, Bach W (2015): Constraints on cooling of the lower ocean crust from epidote veins in the Wadi Gideah section, Oman Ophiolite. Joint IODP/ICDP Colloquium, Bonn, Germany (Poster).
  • Boetius A, Bach W, Borowski C, Diehl A, German CR, Kaul NE, Koehler J, Marcon Y, Mertens C, Molari M, Schlindwein VSN, Türke A, Wegener G, and Science Party of RV POLARSTERN Expedition Aurora PS86 (2014): Exploring the habitability of Ice-covered waterworlds: The deep-sea hydrothermal system of the Aurora Mount at Gakkel Ridge, Arctic Ocean (82°54’ N, 6°15W, 3900 m). American Geoscience Union, Fall Meeting 2014, San Franzisko, USA.