Publication Date:
2017-04-04
Description:
There is considerable evidence for continuing, late-stage interaction
between the magmatic system at Merapi volcano, Indonesia, and
local crustal carbonate (limestone). Calc-silicate xenoliths within
Merapi basaltic-andesite eruptive rocks display textures indicative
of intense interaction between magma and crustal carbonate, and
Merapi feldspar phenocrysts frequently contain crustally contaminated
cores and zones. To resolve the interaction processes between
magma and limestone in detail we have performed a series of
time-variable decarbonation experiments in silicate melt, at magmatic
pressure and temperature, using a Merapi basaltic-andesite
and local Javanese limestone as starting materials.We have used in
situ analytical methods to determine the elemental and strontium isotope
composition of the experimental products and to trace the textural,
chemical, and isotopic evolution of carbonate assimilation.
The major processes of magma^carbonate interaction identified
are: (1) rapid decomposition and degassing of carbonate; (2) generation
of a Ca-enriched, highly radiogenic strontium contaminant
melt, distinct from the starting material composition; (3) intense
CO2 vesiculation, particularly within the contaminated zones; (4)
physical mingling between the contaminated and unaffected melt
domains; (5) chemical mixing between melts. The experiments
reproduce many of the features of magma^carbonate interaction
observed in the natural Merapi xenoliths and feldspar phenocrysts.
The Ca-rich, high 87Sr/86Sr contaminant melt produced in the
experiments is considered as a precursor to the Ca-rich (often
‘hyper-calcic’) phases found in the xenoliths and the contaminated
zones inMerapi feldspars.The xenoliths also exhibit micro-vesicular
textures that can be linked to the CO2 liberation process seen in the
experiments.This study, therefore, provides well-constrained petrological
insights into the problem of crustal interaction at Merapi and
points toward the substantial impact of such interaction on the
volatile budget of the volcano.
Description:
Swedish Science Foundation (Vetenskapsrdet)
Project FIRBMIUR‘Development of innovative technologies for the environmental protection fromnatural events’
Description:
Published
Description:
1027-1051
Description:
2.3. TTC - Laboratori di chimica e fisica delle rocce
Description:
JCR Journal
Description:
open
Keywords:
carbon dioxide
;
experimental petrology
;
magma-carbonate interaction
;
Merapi
;
; strontium isotopes
;
04. Solid Earth::04.08. Volcanology::04.08.03. Magmas
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
Permalink
