Consequences of open-system melting in tectonics

Yakymchuk, Chris; Brown, Michael

doi:10.1144/jgs2013-039

Cited by 124 publications

(150 citation statements)

References 144 publications

(201 reference statements)

Supporting

Mentioning

145

Contrasting

Order By: Relevance

“…It is one of the few methods that allows investigation of the petrological and chemical evolution of deep-crustal rocks, as it provides an opportunity to define equilibrium relationships between melt and solid mineral species for particular bulk compositions at a given set of P-T conditions e.g., [13,14]. Several previous studies have utilised this technique to explore the effects of reintegrating melt back into lower-crustal rocks [16,18,19,41,78,79].…”

Section: Implications Of the Melt Reintegration Modellingmentioning

confidence: 99%

“…Advances in thermodynamic modelling of mineral assemblages have enabled quantitative phase equilibria modelling of the melting processes operating in partially molten siliciclastic rocks in increasingly complex chemical systems [4][5][6][7][8][9][10][11]. These models have been used to investigate the effects of melting and melt loss on crustal rheology, composition and the preservation of geochronometers e.g., [1,5,[12][13][14][15]. However, the application of these models has been limited to theoretical situations, as in almost all real cases there is little information about the composition of the rock prior to melting cf.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Melt Reintegration Modelling: Testing against a Subsolidus Reference Assemblage

et al. 2017

View full text Add to dashboard Cite

Phase equilibria modelling incorporating melt reintegration offers a methodology to create hypothetical rock compositions that may have existed prior to melt loss, allowing the potential prograde evolution of rocks to be explored. However, melt reintegration modelling relies on assumptions concerning the volume of melt that was lost and is generally restricted by the absence of direct constraints on the pre-anatectic mineral assemblages. Mg-rich granulite in the 514-490 Ma Delamerian Orogen in southern Australia contains spinel-cordierite symplectic intergrowths that surround rare, coarse blocky domains of sillimanite. These sillimanite cores, as well as the widespread presence of andalusite in lower grade areas of the southern Delamerian Orogen, suggest that the subsolidus precursor to the granulite contained andalusite. This provides the opportunity to test if melt reintegration modelling of the granulite predicts subsolidus andalusite.Stepwise down-temperature melt reintegration modelling produces a water-saturated solidus after the addition of 12 mol% melt. When modelled at subsolidus conditions, the resulting rock composition produces andalusite-bearing assemblages with andalusite modes similar to the abundance of the sillimanite-cored spinel-cordierite intergrowths. The modelling results from this case study suggest that melt reintegration modelling is a valid method to recreate prograde subsolidus bulk rock compositions.

show abstract

Section: Implications Of the Melt Reintegration Modellingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Melt Reintegration Modelling: Testing against a Subsolidus Reference Assemblage

et al. 2017

View full text Add to dashboard Cite

show abstract

“…The latter were chosen to produce Crd-bearing assemblages, which are common in many regional migmatite terranes, and a peak-T Qtz þ Spl assemblage in which all of the Kfs dissolves into the melt. For simplicity, we consider just isobaric heating and cooling, which allows us to eliminate some variables in an already complex modelling exercise (see Yakymchuk & Brown, 2014).…”

Section: Pressure (P)-temperature (T) Pathsmentioning

confidence: 99%

Crystallization of Heterogeneous Pelitic Migmatites: Insights from Thermodynamic Modelling

Koblinger

Pattison

2017

Journal of Petrology

View full text Add to dashboard Cite

Pelitic migmatites are texturally and mineralogically heterogeneous owing to variable proportions of light and dark coloured domains (leucosome and melanosome), the degree to which the two domains are segregated from one another and the variable composition of the leucosome (tonalitetrondhjemite to alkali feldspar granite). We use thermodynamic modelling to (1) provide insights into the variation in leucosome composition and solidification conditions for different melting and crystallization processes and (2) address the practical problem of how to sample heterogeneous migmatites for the purpose of constraining the pressure-temperature conditions of their formation. The latter is challenging because the appropriate bulk composition is affected by the above heterogeneity, as well as by the possibility of melt loss. Both dehydration melting and excess-water melting (for 2Á0 wt % excess water) are simulated for both equilibrium and fractional melting endmember processes. Three end-member processes are considered during the crystallization stage: (1) fractional crystallization of the melt; (2) equilibrium crystallization of just the melt in isolation from the solid phases; (3) crystallization during which melt and solids maintain chemical communication. Loss of melt during heating and cooling are also considered. Some of the key results of our simulations of pelitic migmatites are as follows. (1) Leucosome composition is primarily a reflection of the melt composition and to lesser degrees the crystallization process and the temperature of melt loss during cooling. Granite (sensu stricto) is the most common leucosome type, arising from many melting and crystallization processes, whereas tonalite or trondhjemite leucosome is generally indicative of excess-water melting. (2) Melts lost from partially molten regions, which have the potential to coalesce and form granites at shallower crustal levels, show less compositional variation than leucosomes in migmatites. Extracted melts are monzogranitic, or rarely granodioritic at low temperatures. (3) Comparing plagioclase compositions between leucosome and melanosome is potentially an effective means of distinguishing between crystallization processes, as well as the degree of retrograde melt-leucosome-melanosome chemical interaction. Fractional crystallization produces zoned plagioclase in the leucosome, isolated equilibrium crystallization produces plagioclase of different composition in the leucosome and melanosome, whereas chemical interaction causes the leucosome and melanosome plagioclase compositions to remain similar during crystallization. (4) The peak temperature of heterogeneous migmatites is most reliably constrained from an equilibrium phase assemblage diagram calculated using just the melanosome composition. Addition of leucosome to the melanosome composition can lead to peaktemperature estimates that differ from actual peak conditions by À25 to þ50 C. In extreme cases, such as in rocks containing high proportions of leucosome to melanosome, or in which...

show abstract

“…For the subsolidus and suprasolidus P-376 T paths, this includes an average amphibolite-facies metapelite (Ague 1991) and an average 377 passive margin greywacke (Yakymchuk and Brown 2014a …”

Section: Bulk Compositions 374mentioning

confidence: 99%

2. Phase Relations, Reaction Sequences and Petrochronology

Yakymchuk¹,

Clark²,

White³

2017

Petrochronology

Self Cite

View full text Add to dashboard Cite

At the core of petrochronology is the relationship between geochronology and the 22 petrological evolution of major mineral assemblages. The focus of this chapter is on outlining 23 some of the available strategies to link inferred reaction sequences and microstructures in 24 metamorphic rocks to the ages obtained from geochronology of accessory minerals and datable 25 major minerals. Reaction sequences and mineral assemblages in metamorphic rocks are 26 primarily a function of pressure (P), temperature (T) and bulk composition (X). Several of the 27 major rock-forming minerals are particularly sensitive to changes in P-T (e.g., garnet, staurolite, 28 biotite, plagioclase), but their direct geochronology is challenging and in many cases not 29 currently possible. One exception is garnet, which can be dated using Sm-Nd and Lu-Hf 30 geochronology (e.g., Baxter et al. 2013). Accessory mineral chronometers such as zircon, 31 monazite, xenotime, titanite and rutile are stable over a relatively wide range of P-T conditions 32 and can incorporate enough U and/or Th to be dated using U-Th-Pb geochronology. Therefore, 33Published in Reviews in Mineralogy, Yakymchuk, C., Clark, C., & White, R. W. (2017). Phase Relations, Reaction Sequences and Petrochronology. Reviews in Mineralogy and Geochemistry, 83(1), 13-53. https://doi.org/10.2138/rmg.2017.83.2 2 linking the growth of P-T sensitive major minerals to accessory and/or major mineral 34 chronometers is essential for determining a metamorphic P-T-t history, which is itself critical 35 for understanding metamorphic rocks and the geodynamic processes that produce them (e.g., 36England and McClelland and Lapen 2013;Brown, 2014). 37Linking the ages obtained from accessory and major minerals with the growth and 38 breakdown of the important P-T sensitive minerals requires an understanding of the 39 metamorphic reaction sequences for a particular bulk rock composition along a well-constrained 40 P-T evolution. Fortunately, the phase relations and reaction sequences for the most widely 41 studied metamorphic protoliths (e.g., pelites, greywackes, basalts) can be determined using 42 quantitative phase equilibria forward modelling (e.g., Powell and Holland 2008). Comprehensive 43 activity-composition models of the major metamorphic minerals in large chemical systems (e.g., 44White et al. 2014a) allow the calculation of phase proportions and compositions for a given rock 45 composition along a metamorphic P-T path. For accessory minerals, subsolidus growth and 46 breakdown can be modelled in some cases using phase equilibria modelling (e.g., Spear 2010; 47 Spear and Pyle 2010). Suprasolidus accessory mineral behaviour can be investigated by coupling 48 phase equilibria modelling with the experimental results of accessory mineral solubility in melt 49 (Kelsey et al. 2008;Yakymchuk and Brown 2014b). This technique provides a basic framework 50 for interpreting the geological significance of accessory mineral ages in suprasolidus 51 metamorphic rocks. 52In this chapter, we use pha...

show abstract

Consequences of open-system melting in tectonics

Cited by 124 publications

References 144 publications

Melt Reintegration Modelling: Testing against a Subsolidus Reference Assemblage

Melt Reintegration Modelling: Testing against a Subsolidus Reference Assemblage

Crystallization of Heterogeneous Pelitic Migmatites: Insights from Thermodynamic Modelling

2. Phase Relations, Reaction Sequences and Petrochronology

Contact Info

Product

Resources

About