Non-ideal interactions in calcic amphiboles and their bearing on amphibole-plagioclase thermometry

Holland, T. J. B.; Blundy, Jon

doi:10.1007/bf00310910

Cited by 2,045 publications

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“…Equilibration temperatures for hornblendeplagioclase assemblages were calculated on the basis of iterations started from pressures calculated using Anderson & Smith (1995) and using various thermometers. Preferred values according to Anderson (1996) have been accepted (see also Anderson et al 2008;Holland & Blundy, 1994). Accordingly, temperature and pressure values were calculated ) and of minettes/leucominettes from Veliki Majdan ) are also displayed.…”

Section: Geology and Petrography Of The Mt Cer Plutonmentioning

confidence: 99%

Petrogenetic and tectonic inferences from the study of the Mt Cer pluton (West Serbia)

et al. 2010

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-The Mt Cer Pluton, Serbia, is a complex laccolith-like intrusion (∼ 60 km 2 ), situated along the junction between the southern Pannonian Basin and northern Dinarides. It intrudes Palaeozoic metamorphic rocks causing weak to strong thermal effects. Based on modal and chemical compositions, four rock-types can be distinguished: (1) metaluminous I-type quartz monzonite/quartz monzodiorite (QMZD); (2) peraluminous S-type two-mica granite (TMG), which intrudes QMZD; (3) Stražanica granodiorite/quartz monzonite (GDS); and (4) isolated mafic enclaves (ME), found only in QMZD. 40 K-39 Ar dating and geological constraints indicate that the main quartz monzonite/quartz monzodiorite body of Mt Cer was emplaced not later than 21 Ma, whereas the emplacement ages of the Stražanica granodiorite/quartz monzonite and two-mica granites are estimated at around 18 and 16 Ma, respectively. The Mt Cer pluton is similar to the Mt Bukulja pluton, some 80 km southwestwards. Genesis of QMZD cannot be interpreted by fractional crystallization coupled with mixing or assimilation. It is best explained by a convection-diffusion process between mantle-derived minette/leucominette magmas and GDS-like magmas followed by two end-member magma mixing. The composition of GDS rocks suggests that GDS-like magmas could have formed by melting of lower crustal lithologies similar to amphibolite/metabasalts. The geochemistry of TMG is reproduced by an Assimilation/Fractional Crystallization model with a ratio of rate of assimilation to rate of fractional crystallization of 0.4, using the compositions of the least evolved TMG of the Bukulja pluton and adjacent metamorphic rocks as proxies for the parental magma and contaminant, respectively. The origin and evolution of the Mt Cer and adjacent Mt Bukulja plutons provide new constraints on the Tertiary geodynamics of the northern Dinarides-southern Pannonian region. The quartz monzonite/quartz monzodiorite is interpreted as a result of the Oligocene post-collisional Dinaride orogen-collapse, which included a limited lithosphere delamination, small-scale mantle upwelling, and melting of the lower crust. By contrast, the two-mica granite magmas formed through melting in shallower crustal levels during the extensional collapse in the Pannonian area.

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Section: Geology and Petrography Of The Mt Cer Plutonmentioning

confidence: 99%

Petrogenetic and tectonic inferences from the study of the Mt Cer pluton (West Serbia)

et al. 2010

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“…[42] Deformation temperature estimates were made using the modified hornblende-plagioclase geothermometer [Holland and Blundy, 1994;Dale et al, 2000] in highly deformed samples 3649-1257 and 3645-1130. Discussion of methods used to processes mineral chemistry data are detailed in Appendix A along with a discussion of error estimation.…”

Section: Gabbro Mineral Chemistry and Plagioclase-hornblende Thermometrymentioning

confidence: 99%

“…[66] Deformation temperature estimates were made using the modified hornblende-plagioclase geothermometer [Holland and Blundy, 1994]. This method uses the DG of two possible equilibria to estimate temperature at varying pressures.…”

Section: A2 Gabbro Mineral Chemistry and Plagioclase-hornblende Thermentioning

confidence: 99%

Strain localization on an oceanic detachment fault system, Atlantis Massif, 30°N, Mid‐Atlantic Ridge

Schroeder

John

2004

Geochem Geophys Geosyst

153

217

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[1] Microstructural observations, mineral chemistry, and the spatial distribution of deformation fabrics recorded in outcrop samples collected from Atlantis Massif, the active inside corner high at 30°N, MidAtlantic Ridge, suggest that strain is localized near the subhorizontal domal surface hypothesized to be an exposed detachment fault. Deformation textures in peridotite and gabbro indicate that high-temperature (>500°C) strain occurred via crystal-plastic flow and diffusive mass transfer. Low-temperature (<400°C) shear zones containing brittle and semibrittle microboudinage textures in which tremolite, chlorite, and/or talc replace fractured serpentine or hornblende cut earlier formed high-temperature deformation fabrics in peridotite. Textures indicate strain was localized by cataclasis and reaction softening into zones of intense greenschist and subgreenschist grade metamorphism. Gabbro is only weakly deformed below amphibolite facies (<500°C), indicating that strain was partitioned into altered peridotite at low temperature. There is a clear relationship between deformation intensity and structural depth beneath the subhorizontal surface of the Massif. Discontinuous high-intensity crystal-plastic deformation fabrics are found at all structural depths (0-520 m) beneath the surface, indicating that high-temperature, granulite-and amphibolite-grade deformation was not localized in a single shear zone. In contrast, semibrittle and brittle low-temperature shear zones are concentrated less than 90 m structurally beneath the surface, and the most intensely brittlely deformed samples concentrated in the upper 10 m. Localization of brittle deformation fabrics near the upper surface of the massif supports the hypothesis that it is the exposed footwall of a detachment fault. The structural evolution of Atlantis Massif is therefore analogous to a continental metamorphic core complex. Strain was localized onto the fault by reaction-softening and fluid-assisted fracturing during greenschist-and subgreenschist-grade hydrothermal alteration of olivine, clinopyroxene, serpentine, and hornblende to tremolite, chlorite, and/or talc.

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“…Natural and synthetic oxides and silicates were used as standards for major elements. Structural formulas for all amphiboles were calculated according to Holland & Blundy (1994). We used the Mathematica package based software (PET) (Dachs 2004) for mineral formula calculation (including the nomenclature for amphibole according to the IMA scheme), calculation and plotting of mineral compositions.…”

Section: Electron Microprobe Analytical Techniquementioning

confidence: 99%

“…In order to evaluate the depth of origin of material and the depth of intrusion of the mafic dykes, temperature and pressure were calculated using the PET software (Dachs 2004) based on the hornblende-plagioclase thermometer of Holland & Blundy (1994) and the aluminum-in-hornblende barometer (Hammarstrom & Zen 1986;Hollister et al 1987) respectively.…”

Section: Pressure and Temperature Constraintsmentioning

confidence: 99%

Geochemical and isotopic evidence for Carboniferous rifting: mafic dykes in the central Sanandaj-Sirjan zone (Dorud-Azna, West Iran)

Shakerardakani¹,

Neubauer²,

Bernroider³

et al. 2017

Geologica Carpathica

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Abstract:In this paper, we present detailed field observations, chronological, geochemical and Sr-Nd isotopic data and discuss the petrogenetic aspects of two types of mafic dykes, of alkaline to subalkaline nature. The alkaline mafic dykes exhibit a cumulate to foliated texture and strike NW-SE, parallel to the main trend of the region. The 40 Ar/ 39 Ar amphibole age of 321.32 ± 0.55 Ma from an alkaline mafic dyke is interpreted as an indication of Carboniferous cooling through ca. 550 °C after intrusion of the dyke into the granitic Galeh-Doz orthogneiss and Amphibolite-Metagabbro units, the latter with Early Carboniferous amphibolite facies grade metamorphism and containing the Dare-Hedavand metagabbro with a similar Carboniferous age. The alkaline and subalkaline mafic dykes can be geochemically categorized into those with light REE-enriched patterns [(La/Yb) N = 8.32-9.28] and others with a rather flat REE pattern [(La/Yb) N = 1.16] and with a negative Nb anomaly. Together, the mafic dykes show oceanic island basalt to MORB geochemical signature, respectively. This is consistent, as well, with the (Tb/Yb) PM ratios. The alkaline mafic dykes were formed within an enriched mantle source at depths of ˃ 90 km, generating a suite of alkaline basalts. In comparison, the subalkaline mafic dykes were formed within more depleted mantle source at depths of ˂ 90 km. The subalkaline mafic dyke is characterized by 87 Sr/ 86 Sr ratio of 0.706 and positive ɛ Nd (t) value of + 0.77, whereas 87 Sr/ 86 Sr ratio of 0.708 and ɛ Nd (t) value of + 1.65 of the alkaline mafic dyke, consistent with the derivation from an enriched mantle source. There is no evidence that the mafic dykes were affected by significant crustal contamination during emplacement. Because of the similar age, the generation of magmas of alkaline mafic dykes and of the Dare-Hedavand metagabbro are assumed to reflect the same process of lithospheric or asthenospheric melting. Carboniferous back-arc rifting is the likely geodynamic setting of mafic dyke generation and emplacement. In contrast, the subalkaline mafic sill is likely related to the emplacement of the Jurassic Darijune gabbro.

show abstract

Non-ideal interactions in calcic amphiboles and their bearing on amphibole-plagioclase thermometry

Cited by 2,045 publications

References 75 publications

Petrogenetic and tectonic inferences from the study of the Mt Cer pluton (West Serbia)

Petrogenetic and tectonic inferences from the study of the Mt Cer pluton (West Serbia)

Strain localization on an oceanic detachment fault system, Atlantis Massif, 30°N, Mid‐Atlantic Ridge

Geochemical and isotopic evidence for Carboniferous rifting: mafic dykes in the central Sanandaj-Sirjan zone (Dorud-Azna, West Iran)

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