The Ballachulish Igneous Complex, Scotland: Petrography, Mineral Chemistry, and Order of Crystallization in the Monzodiorite-Quartz Diorite Suite and in the Granite

Weiss, S.; Troll, Georg

doi:10.1093/petrology/30.5.1069

Cited by 49 publications

(28 citation statements)

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“…However, upward displacement of Al-solubility temperatures would result in extreme temperatures in excess of 1ooo"C from many rocks in the Minto area studied by BCgin & Pattison 1994), inconsistent with the absence of sapphirine and extreme rarity of spinel + quartz in aluminous Gt + Crd + Sil paragneisses that would be expected at such temperatures (see petrogenetic grids of Harley, 1989;Hensen & Harley, 1990). Additionally, the high SB and LG Fe-Mg temperatures from Ballachulish are inconsistent with numerous other data in the aureole and igneous complex (Weiss & Troll, 1989Masch & Heuss-Assbichler, 1991;Pattison, 1991).…”

Section: Constraints On Calibration Accuracy From Zoning Patte C N Smentioning

confidence: 84%

Zoning patterns in orthopyroxene and garnet in granulites: implications for geothermometry

Pattison

Bégin

1994

Journal Metamorphic Geology

153

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Compositional maps of orthopyroxene and garnet of contrasting grain size and in contact with different minerals were made from two paragneiss granulites from the Minto terrane of northern Quebec. The compositional maps provide clear evidence of late exchange of Fe/(Fe + Mg) after Ca in garnet and A1 in orthopyroxene had been quenched-in. The extent of late Fe-Mg exchange was controlled by neighbouring minerals, with negligible Fe-Mg gradients against plagioclase and quartz, and substantial gradients against exchangeable Fe-Mg minerals. Cores of grains in contact with exchangeable Fe-Mg neighbours are progressively more reset in Fe/(Fe + Mg) as grain size decreases, whereas cores of even small grains surrounded by only plagioclase and quartz are not significantly different in Fe/(Fe + Mg) than cores of the largest grains. Gradients of Ca in garnet and of Al in orthopyroxene in grains of uniform Fe/(Fe + Mg) preserve a high-temperature retrograde history during which intergranular exchange effected compositional uniformity of mineral rims and intragranular Fe-Mg diffusion in garnet and orthopyroxene was rapid enough to homogenize Fe/(Fe + Mg). The transition from efficient intergranular exchange at relatively high temperatures to local Fe-Mg exchange at lower temperatures may have been controlled by loss of an intergranular exchange medium in the rock, possibly an internally generated dehydration melt phase. Implications for geothermometry of granulites include the following (numerical values are particular to this study): (1) core compositions of garnet and orthopyroxene grains in contact with exchangeable neighbours may be reset in Fe/(Fe + Mg) relative to the most refractory compositions by an amount equivalent to 120°C; (2) Fe-Mg exchange thermometry using even the most refractory Fe/(Fe + Mg) compositions may not record peak granulite conditions, possibly recording instead the temperature at which an intergranular exchange medium was lost from the rock; and (3) temperaturesensitive net transfer equilibria involving Al solubility in orthopyroxene yield temperatures up to 150" C higher than maximum Fe-Mg exchange temperatures, even in grains with flat Fe/(Fe + Mg) compositional profiles, making them a better means of estimating peak granulite temperatures than Fe-Mg exchange thermometry.

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Section: Constraints On Calibration Accuracy From Zoning Patte C N Smentioning

confidence: 84%

Zoning patterns in orthopyroxene and garnet in granulites: implications for geothermometry

Pattison

Bégin

1994

Journal Metamorphic Geology

153

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“…In both cases, the resulting anomalies have wavelengths of <50 km. The predominance of induced over remanent magnetization can be predicted from the presence of coarse-grained (>1 mm) magnetite in the Minto rocks, suggesting a multidomain microstincture that is conducive to large susceptibilities but low stable remanent magnetization levels, a characteristic of several plutonit rock suites [Henkel, 1991[Henkel, , 1994 [Petersen, 1980;Eggins and Hensen, 1987;Weiss and Troll, 1989;Lahti, 1995] support linkages between early, hightemperature crystallization of pyroxenes and compositionally evolved, hydrous granitoid rocks. Crustal xenolith suites from areas with associated LWA could be queried for igneous chamockitic components to assess the validity of this conjecture.…”

Section: Susceptibility Measurementsmentioning

confidence: 97%

Crustal magnetization and long‐wavelength aeromagnetic anomalies of the Minto block, Quebec

Pilkington¹,

Percival²

1999

J. Geophys. Res.

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“…A depth of intrusion of around 10km [Pattison, 1989] suggests the country rocks were 250-300°C pre-emplacement, assuming a normal geothermal gradient. Maximum temperatures of 1100°C were attained within the igneous body [Weiss and Troll, 1989], leading to contact-metamorphism of the country rock at up to 850°C [Lind, 1996], although estimates vary. Contact metamorphism is thought to have lasted around 500k.y., including around 270k.y.…”

Section: 2) Thermal Conditions In the Aureolementioning

confidence: 99%

Using titanium-in-quartz geothermometry and geospeedometry to recover temperatures in the aureole of the Ballachulish Igneous Complex, NW Scotland

Morgan

Jollands

Lloyd

et al. 2013

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Titanium--in--Quartz geothermometry, originally pioneered by Wark and Watson [2006] then later modified by Kawasaki and Osanai [2008] and Thomas et al. [2010] promises accurate quartz crystallisation temperature determinations from straightforward measurements of Ti within the quartz lattice. These geothermometers are tested by applying them to a suite of contact metamorphosed quartzites from around the Ballachulish Igneous Complex in West Scotland. Results show that the original Ti--in--Quartz geothermometer gives results broadly in agreement with thermal modelling and pre--existing geothermometry data from Ballachulish and the latter geothermometers give temperatures which are consistently too low. However, despite a broad agreement between published temperature values and those derived from the original thermometer of Wark and Watson [2006], there is a lack of correlation between distance from the igneous contact and determined temperature, as well as unacceptably large errors in some cases. Furthermore, a rigorous test of the methodology employed in this and other studies suggests that the system is more complex than assumed, and a greater understanding of the substitution of other elements in quartz (such as aluminium) is necessary. In addition, various issues have been raised by other workers regarding the validity of Ti--in--Quartz as a geothermometry tool at all, inasmuch as the original equations were constructed with a disregard for a range of complicating factors. This study adds further weight to a growing mass of critiques of this technique of geothermometry and suggests a much greater understanding of the processes is necessary before Ti--in--Quartz can be convincingly upheld as a viable tool.

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The Ballachulish Igneous Complex, Scotland: Petrography, Mineral Chemistry, and Order of Crystallization in the Monzodiorite-Quartz Diorite Suite and in the Granite

Cited by 49 publications

References 0 publications

Zoning patterns in orthopyroxene and garnet in granulites: implications for geothermometry

Zoning patterns in orthopyroxene and garnet in granulites: implications for geothermometry

Crustal magnetization and long‐wavelength aeromagnetic anomalies of the Minto block, Quebec

Using titanium-in-quartz geothermometry and geospeedometry to recover temperatures in the aureole of the Ballachulish Igneous Complex, NW Scotland

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