Constraints on pre-eruptive magmatic history using multi-faceted diffusion modeling: an analytical, experimental and numerical study

Rout, Smruti Sourav

dc.contributor.advisor	Wörner, Gerhard Prof. Dr.
dc.contributor.author	Rout, Smruti Sourav
dc.date.accessioned	2020-05-28T14:51:42Z
dc.date.available	2020-05-28T14:51:42Z
dc.date.issued	2020-05-28
dc.identifier.uri	http://hdl.handle.net/21.11130/00-1735-0000-0005-13B8-6
dc.identifier.uri	http://dx.doi.org/10.53846/goediss-7995
dc.language.iso	eng	de
dc.rights.uri	http://creativecommons.org/licenses/by-nc-nd/4.0/
dc.subject.ddc	910	de
dc.subject.ddc	550	de
dc.title	Constraints on pre-eruptive magmatic history using multi-faceted diffusion modeling: an analytical, experimental and numerical study	de
dc.type	doctoralThesis	de
dc.contributor.referee	Wörner, Gerhard Prof. Dr.
dc.date.examination	2020-01-22
dc.description.abstracteng	Time-scales extracted from chemically zoned minerals provide insights into crystal residence time, magma storage and compositional evolution of magmas and allow better constraints on pre-eruptive history of large and potentially dangerous magma chambers. We applied diffusion chronometry to different eruption products from Laacher See volcano (Germany) and Taapaca volcano (Chile). (a) Laacher See volcano: (1) Diffusion modeling of Ba-diffusion across outermost resorption interfaces in sanidine phenocrysts constrains the time between magma mixing and eruption to be 4-8 years. Diffusion time-scales obtained from interior resorption and regrowth zones suggest a recharge frequency of every 1.5-3 ky in the past ~24 ky history of the mama reservoir. (2) Carbonatitic syenites are interpreted to represent a crystallizing carapace around the phonolite magma. The pre-eruptive, core-rim Na-K diffusion in sanidines constrains the effective storage temperature at 630-670 ᵒC. These values along with a conduction model constrain the radial inward growth rate of the syenite carapace at ~8 cm/year. Uphill diffusion modeling across exsolution boundaries in sanidine gave a maximum time between the destabilisation of the carapace and eruption of only 40-50 days. (3) Crystal mushes that form accumulation of phenocrysts are generally devoid of zoned crystals. Only crystals with resorbed boundaries or very thin overgrowths (a few microns) with very sharp compositional changes imply the activation of cumulates only months before eruption. (b) Taapaca volcano: Sanidine megacrysts in dacites show repetitive, sharp jumps in Ba concentration at resorption interfaces that reflect frequent heating events during their growth. These distinct growth bands formed at temperatures of ~720 to 820 ᵒC pressures of 1-3 kbar based on amphibole-plagioclase thermometry and Al-in-Hornblende barometry for each growth zone separately. A non-isothermal diffusion modeling was tested experimentally using halogen diffusion and further developed in terms of precision. The new algorithm was applied to Ba-profiles across individual diffusive boundaries to give diffusion times ranging from 0.4 to 490 ky and total residence times of 9 to 499 ky for different crystals from different stages of eruption. All crystals show late oscillatory overgrowths that indicate multiple heating events in the magmatic system at increased frequency only ~0.4 to 3 ky before eruption. Based on these diffusion times and storage temperatures, genetic models for the process and timing of storage and activation are presented for both the magma systems with respect to the current discussions regarding cold- versus hot-storage models.	de
dc.contributor.coReferee	Webb, Sharon Prof. Dr.
dc.contributor.thirdReferee	Pack, Andreas Prof. Dr.
dc.contributor.thirdReferee	Kronz, Andreas Dr.
dc.contributor.thirdReferee	Schmidt, Burkhard Dr.
dc.contributor.thirdReferee	Holtz, François Prof. Dr.
dc.subject.eng	Diffusion modeling	de
dc.subject.eng	Laacher See	de
dc.subject.eng	Taapaca volcano	de
dc.subject.eng	Non-isothermal diffusion	de
dc.subject.eng	Magma storage	de
dc.subject.eng	Chronometry	de
dc.identifier.urn	urn:nbn:de:gbv:7-21.11130/00-1735-0000-0005-13B8-6-3
dc.affiliation.institute	Fakultät für Geowissenschaften und Geographie	de
dc.subject.gokfull	Geologische Wissenschaften (PPN62504584X)	de
dc.identifier.ppn	1699000719