Trace element composition and cathodoluminescence of kyanite and its petrogenetic implications

Müller, Axel; Kerkhof, Alfons M. van den; Selbekk, Rune S.; Broekmans, Maarten A. T. M.

doi:10.1007/s00410-016-1280-6

Cited by 13 publications

(47 citation statements)

References 59 publications

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“…() and Müller et al. () to be linked to oxygen fugacity during kyanite growth, as they observed elevated Fe in kyanite in oxidised rocks. The subtle Ky1b to Ky2 Fe enrichment could therefore be indicative of changing f O 2 during metamorphism, though the zonation could also be caused by minerals of different Fe content breaking down in kyanite‐forming reactions (e.g., muscovite v .…”

Section: Kyanite Chemical Compositionmentioning

confidence: 92%

“…Müller et al. () found a positive correlation between trace Ti in kyanite and growth temperature, and suggested that Ti incorporation in kyanite is dependent on temperature. Here, however, retrograde rims in each sample formed by the same reaction at similar temperatures, and show different trends relative to prograde kyanite.…”

Section: Kyanite Chemical Compositionmentioning

confidence: 99%

“…As garnet is consumed during melt crystallization, these rims partially break down, which may explain the characteristic Cr enrichment of retrograde kyanite. Differences in average Cr in kyanite between samples may be a function of the bulk composition of the samples (Müller et al., ). Iron in kyanite, assumed to be Fe 3+ , has been suggested by Chinner et al.…”

Section: Kyanite Chemical Compositionmentioning

confidence: 99%

“…An investigation of kyanite CL by Müller et al. () focused on a variety of rock types including metapelites, felsic granulites, and metamorphosed alteration zones, and also found some examples of a core and rim with distinct CL signatures in kyanite grains. These findings attest to the potential of CL imaging for highlighting the subtle changes in trace element composition that delineate kyanite growth zones, which can then be linked to the metamorphic history.…”

Section: Introductionmentioning

confidence: 99%

“…Kyanite has a simple chemical composition (Al 2 SiO 5 ), but it may contain significant concentrations of trace elements, in particular Cr, Ti, V and Fe, along with others (Chinner, Smith, & Knowles, 1969;Herz & Dutra, 1964;Hietanen, 1956;M€ uller, van den Kerkhof, Selbekk, & Broekmans, 2016;Pearson & Shaw, 1960). Trace elements have been found to record and reveal growth zonation particularly well relative to major elements in some metamorphic minerals, most notably garnet (Spear & Kohn, 1996).…”

Section: Introductionmentioning

confidence: 99%

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The reaction history of kyanite in high‐P aluminous granulites

Kendrick

Indares

2017

Journal Metamorphic Geology

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Cathodoluminescence (CL) mapping of kyanite in high pressure, aluminous granulites from the central Grenville Province reveals internal structures that are linked to their metamorphic reaction history. In two samples, individual kyanite crystals are shown to be composite porphyroblasts comprising three distinct generations, defined by their CL intensity and Cr (±V, Ti, Fe and Ga) content, and each separated by resorbed interfaces. In contrast, a sub‐aluminous sample contains two types of kyanite, one as resorbed inclusions in garnet and another in the groundmass or replacing garnet. These textural variants of kyanite are interpreted within the framework of phase equilibria modelling. In P–T pseudosections, a first generation of kyanite, which is only present in the most aluminous samples, is potentially linked to staurolite breakdown, and its resorption is consistent with a subsequent increase in pressure. This kyanite represents the earliest remnant of prograde metamorphism identifiable in these rocks. The second generation, present in the porphyroblasts in the same samples and as inclusions in garnet in the sub‐aluminous sample, is interpreted to be the peritectic product of muscovite dehydration melting. Resorption of this kyanite is consistent with subsequent continuous dehydration melting of biotite, which is also inferred based on microstructural considerations. The final generation of kyanite, present as rims on the prograde kyanite porphyroblasts in aluminous samples and as part of the groundmass or replacing garnet in the sub‐aluminous rock, is interpreted to have grown during melt crystallization upon retrogression. The presence of retrograde kyanite implies that the melt crystallized over a wide range of temperatures, and provides an important constraint on the P–T conditions of the metamorphic peak and on the retrograde P–T path. CL mapping is crucial for identifying retrograde kyanite in aluminous samples, as it preferentially overgrows existing kyanite rather than replacing other prograde phases. The scarcity of kyanite in sub‐aluminous rocks allows retrograde kyanite to grow as discrete crystals that can be identified by optical microscopy. This work attests to the potential of unconventional tools such as CL imaging for deciphering the metamorphic history of rocks.

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Section: Kyanite Chemical Compositionmentioning

confidence: 92%

Section: Kyanite Chemical Compositionmentioning

confidence: 99%

Section: Kyanite Chemical Compositionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The reaction history of kyanite in high‐P aluminous granulites

Kendrick

Indares

2017

Journal Metamorphic Geology

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Pressure-enforced Cr substitution in Cr1+xAl1−xO(SiO4), synthetic analogues of kyanite

et al. 2019

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Cr 3+ can substitute for Al 3+ in the crystal structure of kyanite, Al 2 O(SiO 4). Cr 3+-rich solid solutions along the binary Al 2 O(SiO 4)-Cr 2 O(SiO 4) joint were synthesized under distinct high-pressure conditions. Sample crystals of Cr 1+x Al 1−x O(SiO 4) with x = 0.025(12) and 0.188(8) have been synthesized at pressures of 7 GPa and temperatures up to 1200 °C. Unit-cell dimensions and single-crystal X-ray diffraction of the new Cr 3+-rich kyanite-type phases show a linear increase of lattice parameters a, b and c with increasing Cr 3+ content. Cr 3+ replaces Al 3+ on the octahedrally coordinated M-sites with Cr 3+ preferentially occupying large [MO 6 ]-octahedra. Cr 3+ substitution for Al 3+ is highest on the M3 site in a sequence of Cr 3+ (M3) > Cr 3+ (M2) > Cr 3+ (M1) > Cr 3+ (M4) following the polyhedral volumes V(M3O 6) > V(M2O 6) > V(M1O 6) > V(M4 O 6). The compressibility of Cr 1.19 Al 0.81 O(SiO 4) has been determined via precise lattice parameters up to 6.00(4) GPa. The pressure-volume data fitted to the third-order Birch-Murnaghan equation of state yielded an isothermal bulk modulus (K T0) of 196(16) GPa and a pressure derivative K′ T0 of 2(4) at V 0 = 310.3(1) Å 3. The value of K T0 is in accordance to the Anderson-Anderson relation but it is slightly smaller than the respective value for natural Cr 3+-free kyanite.

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