Publication Date:
2021-03-29
Description:
As has been demonstrated in recent years, the
heterogeneities of coeval magmas can be more successfully
revealed by zoned megacrysts rather than by analysis of the
whole rocks hosting them. Here, the geochemical heterogeneities
of feldspar megacrysts from the Karkonosze
granite, Poland, are investigated by LA-ICP-MS. The crystals
are the product of migration and growth in regions of
poorly mixed magmas. 3D-modeling of the Ba, Sr, and Rb
distributions emphasizes the importance of micro-domain
growth morphologies. Two models of element behavior—a
relative concentration model and a composition gradient
model—provide a potentially effective tool for tracking the
mixing process on a microscale. Measured concentrations of
elements of different mobilities do not agree with what
might be expected from the mixing of two end-member
magmas. If mixing was the only process occurring, linear
correlations between the concentrations of any two elements
should be observed; this, however, is not the case. For
combinations of any two of the three elements, modeling
reveals differing non-linear correlations between concentrations.
The megacryst heterogeneities provide an insight
into how mixing magmas are chaotically advected to
growing crystals and the degree of inter-magma element
exchange between the magmas.
Keywords:
Mixing; Element mobility; Diffusion; Alkali feldspar; 3D-depiction; Cut-off value models; Gradient models; Probabilistic models; Geochemical heterogeneity; Karkonosze granite
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551
Language:
English
Type:
article
,
publishedVersion
