EAG

Home

  • Program

    The Goldschmidt2020 program

  • Venue

    All about the venue and city

  • Registration

    Details of how to register to attend the conference and/or submit an abstract

  • Exhibition

    Information for and about exhibitors and sponsors

  • My Goldschmidt

    My program, purchases, connections, etc.

Home

Program

Events

  • Sponsor Seminars

  • Training Events

    These are scheduled events to help delegates test out the tools and platform we will be using for the Q&A and other events at the conference.

  • Workshops

    Our workshop program provides training and teaching in topics across geochemistry and related fields. We are currently liaising with the workshop organisers to ascertain if any workshops can become virtual. Any updates will be added to this page.

Locations

  • Conference Locations

    Location of the convention center and social events

  • Hotels

    The hotels are no longer available to book at the special rates agreed by the conference. Should you wish to cancel or change your hotel reservation please see the details below.

Information

Present your work

Attend

Exhibition

Sponsorships

My Goldschmidt

Role functions

Abstract Details

(2020) Slab Temperature Control on Volatile Budgets of Arc Magmas Tracked from Melt Inclusion Halogen Contents

Brahm R, Kuritani T, Sakamoto N, Yurimoto H, Zellmer G, Nakagawa M & Sato E

https://doi.org/10.46427/gold2020.253

Sorry, the PDF cannot be displayed on your browser.

Download abstract

The author has not provided any additional details.

05d: Room 2, View in program

Listed below are questions that have been submitted by the community that the author will try and cover in their presentation. To submit a question, ensure you are signed in to the website. Authors or session conveners approve questions before they are displayed here.

Submitted by Lucy McGee on
Hi Raimundo - great study! Amazing how distinct those 7 centres are in their trace element contents. On your figure of Pb/Ce vs. F/Y what is the difference between 'slab fluid flux signal' (vertical arrow) and '%slab fluid in melt' (horizontal arrow)? Also, are there any other cases where you get slab melting way out in the back arc? Or is that a very unique scenario? Thanks and best wishes! Lucy
Hi Lucy, thank you! By slab fluid signal I refer to the flux of slab fluid added to the mantle source, whereas %slab fluid in melt refers to the final proportion of the slab component in the generated magma. I think we are seeing a dilution effect, where a low degree of fluid flux into the source mantle produces low melt volumes or low degree partial melts. This process results in high fluid concentrations in the primary melt. Rishiri’s tectonic setting is distinct. It is very far from the trench, and the slab surface under it reaches almost 8GPa. I would not know if it is comparable to any other back-arc volcano. Hydrous silicate melts have been invoked to explain particular geochemical signals of other volcanic systems, but I don’t think that any of it is directly comparable to this particular rear-arc setting. As I said in the presentation, Rishiri’s halogen compositions are remarkably similar to those found in an olivine-hosted melt inclusion group from Mt. Shasta (Le Voyer et al., 2010), which is not a back-arc setting. Slab temperature conditions might be closer to a back-arc setting as subduction rate is very low in the Cascades.
Submitted by Diego F. Narváez on
Could it be possible that there is phlogopite in the mantle wedge under Rishiri volcano? if so, it would affect the F/Cl ratio. Have you considered that?
Hi Diego, thanks for the question. I have not yet explored the possibility of phlogopite involvement in the F/Cl ratio shift in the rear-arc. Nonetheless, as this change is accompanied with enrichment of incompatible but immobile elements like Zr, I am inclined to think that the most probable cause of higher F/Cl is a change in the nature of the slab liquid (silicate melt or supercritical fluid). The somewhat narrow range of F/Cl ratios from arc to back-arc (excluding Rishiri volcano) makes me think that the process of fluid release should be a continuous dehydration reaction of a particular lithology, which I believe to be serpentinites. Serpentinites can be present and continuously dehydrated as subduction progresses. Kendrick et al. (2020) and their presentation in this conference, found that the halogen signals of arc and back-arc magmas (using F, Cl, I and Br) are probably inherited from the serpentinites from the metasomatized slab lithospheric mantle. Again, the change towards the rear-arc is indicating a shift on the controlling reaction of fluid release, which needs to start transporting more immobile elements from a source already depleted of mobile elements through progressive dehydration.
Submitted by Emily Johnson on
Hello Raimundo, Excellent study! The very high Cl and F are interesting, and yes, similarly high F and Cl are found at Shasta, but not elsewhere in the Cascades (to my knowledge) although slab Ts remain quite high along the arc. What about the possibility of a subducted fracture zone or seamounts that could contribute volatiles? Thanks again for a great talk!

Sign in to ask a question.

Geochemical Society, an organization registered in USA. Address: 5241 Broad Branch Road, NW Washington, DC 20015-1305.
Tel: +44 1223 852663. Email: helpdesk@goldschmidt.info

Goldschmidt® is a registered trademark of the Geochemical Society and of the European Association of Geochemistry

Conference management and website by White Iron Conferences

Main photograph © Kenneth Rubin