Regression diagnostics and robust regression in geothermometer/geobarometer calibration: the garnet-clinopyroxene geothermometer revisited   总被引：25，自引：1，他引：25  

ROGER POWELL 《Journal of Metamorphic Geology》1985,3(3):231-243

Abstract The calibration of geothermometers and geobarometers should involve not only the determination of the parameters in the equation used, but also the uncertainties on, and the correlations between, these parameters. This necessitates the use of a technique such as least squares. Given the poor performance of least squares in the presence of outliers in the data, techniques for identifying outliers for exclusion—regression diagnostics, and techniques for handling data which include outliers—robust regression and jackknifing, are essential. These techniques are summarized and their importance is emphasized, and they are applied to the calibration of the garnet-clinopyroxene Fe-Mg exchange geothermometer.
The experimental data of Raheim & Green (1974) and Ellis & Green (1979) are explored using regression diagnostics to discover outliers in the data. After exclusion of the two influential outliers found, a new geothermometer equation for garnet-clinopyroxene Fe-Mg exchange is derived using robust regression and based on all the data: thus, T (K) = 2790 + 10 P + 3140x_ca,g/1.735 + In K _D where T is in Kelvin and P is in kbar. This equation, as might be hoped, is essentially identical to that of Ellis & Green (1979). Equations for calculating the uncertainty in a calculated temperature, contributed by uncertainties in the calibration, are also derived.  相似文献   

Precambrian granulites of the Aldan shield, eastern Siberia, USSR   总被引：17，自引：0，他引：17  

L. L. PERCHUK  L. Ya. ARANOVICH  K. K. PODLESSKII  I. V. LAVRANT'EVA  V. Yu GERASIMOV  V. V. FED'KIN  V. I. KITSUL  L. P. KARSAKOV  N. V. BERDNIKOV 《Journal of Metamorphic Geology》1985,3(3):265-310

Abstract Precambrian granulites of the Aldan shield in southern Yakutia, USSR, form a massif of 200,000 km² bounded by younger fold-belts to the south, west and east. The massif consists of several blocks that reflect a primary heterogeneity of composition and differences in structural and thermodynamic evolution of different parts of the area. According to structural and petrological data the massif can be divided into two megablocks: eastern Aldan and western Aldan. They are separated by a narrow meridional fold-belt. Structural evolution of this central zone was determined by the geodynamics of the mega-blocks and was completed in the late Archaean. Towards the south, this central zone is ‘transformed’into the relatively small Sutam block adjoining the Stanovoy fold-belt that bounds the Aldan shield on the south. The Sutam block is separated from the other structural units of the Aldan shield by a system of north trending grabens filled by post-Archaean sediments. The Aldan shield is composed of Archaean high-grade granulites, while the Stanovoy fold-belt, to the south, consists of highly foliated Proterozoic rocks metamorphosed under relatively lower-grade conditions. However, relics of the granulites are mapped within the fold-belt. They contain high-grade assemblages (e.g. Opx + Sil + Qz, Sap + Qz, Opx + Gr + Sil, etc.). One of the relics, the Tokskii block, which is only slightly touched by diaphthoresis, is located in the southeastern part of the Stanovoy fold-belt. Metamorphic conditions of the Tokskii block are compared with those of the Sutam block and a similar evolution of the units is revealed. Mineral assemblages and mineral compositions do not vary within each unit, but they change in a north-south direction. The Opx + Sil + Qz assemblage has been found only in Sutam and Tok, but not in eastern Aldan and western Aldan. The Sap + Qz assemblage has been found in the Tokskii block but has not yet been found in the Sutam block. The pyrope content in garnets, from metapelites of both blocks, is significantly higher than that from the Aldan (eastern and western blocks) rocks to the north. The most important assemblages from different units of the Aldan shield have been studied using the electron microprobe in order to unravel the metamorphic evolution of the granulites and thus to deduce the thermodynamic regime of this evolution. A geodynamic model for the Aldan shield is discussed in terms of Archaean island arc development.  相似文献   

Aluminous reaction textures in orthoamphibole-bearing rocks: the pressure–temperature evolution of the high-grade Proterozoic of the Bamble sector, south Norway     

D. VISSER  A. SENIOR 《Journal of Metamorphic Geology》1990,8(2):231-246

Aluminous reaction textures in orthoamphibole-bearing rocks from the Froland area, Bamble, south Norway, record the prograde pressure–temperature path of the high-grade Kongsbergian Orogeny (c. 1600–1500 Ma) and the low–mid amphibolite facies overprint during the Sveconorwegian Orogeny (c. 1100–1000 Ma). The rocks contain anthophyllite/gedrite, garnet, cordierite, biotite, quartz, andalusite, kyanite, Cr-rich staurolite, tourmaline, ilmenite, rutile and corundum in a variety of parageneses. The P–T path is deduced from petrographic observations, mineral chemistry and zoning, geothermometry and (N)FMASH equilibria. The results indicate the sequence of metamorphic stages outlined below. (a) An M₁ phase characterized by the presence of strongly deformed andalusite, gedrite and tourmaline. (b) An M₂ phase with the development of kyanite after andalusite and the growth of staurolite associated with strong Na–Al–Mg zoning in orthoamphibole, indicating an increase in pressure (4 8 kbar) and temperature (500° 650°C). (c) Pressure decrease at high P (6–7 kbar) and high T (600–700 °C) during M_3a with the production of cordierite ° Corundum between kyanite, staurolite and orthoamphibole and cordierite growth between corundum and orthoamphibole. (d) Temperature increase to 740 ± 60 °C and 7 kbar; static growth of garnet (M_3b) at the metamorphic climax (peak T). The heat supply necessary to explain the temperature increase between the M_3a and M_3b phases is correlated with synkinematic enderbitic–charnockitic and basic intrusions in the Arendal granulite facies terrain. (e) M_3b metamorphic conditions were followed by an initial isobaric cooling path (early M₄) and late-stage pressure decrease (late M₄). Early M₄ conditions of 6–7 kbar and 550–600 °C, assuming P_H2O < P_total are indicated by a retrograde talc–kyanite–quartz assemblage in late quartz–cordierite veins. Late M₄ conditions of 3–4 kbar and 420–530 °C are inferred from a kyanite–andalusite–chlorite–quartz assemblage in vein-cordierite. The M₁–M₃ stages are interpreted as being the result of the same metamorphic P–T path, which was caused by both tectonic and magmatic thickening. A prolonged crustal residence time is proposed for the Bamble sector before uplift during the later stages of M₄ occurred.  相似文献   

Plagioclase ultraphyric basalts in Iceland: the mush of the rift   总被引：1，自引：0，他引：1  

H. Hansen  K. Grnvold 《Journal of Volcanology and Geothermal Research》2000,98(1-4)

Glassy, plagioclase ultraphyric basalts from six locations in Iceland have bimodal phenocryst size distributions where microphenocrysts (ol+plg±cpx±mt) are in equilibrium with the matrix glass, but macrophenocrysts (ol+plg±cpx) are too primitive to be so. Matrix glass compositions are similar to those of other rift zone glasses from Iceland, and oxygen isotope variations suggest they interacted with the Icelandic crust. A lack of negative Eu-anomalies in matrix glasses precludes large amounts of plagioclase crystallisation from their parental liquids. Compositions of glass inclusions in plagioclase and olivine macrophenocrysts indicate that parental magma compositions of the macrophenocryst assemblage are similar to those of primitive, Icelandic rift zone glasses. Temperatures for plagioclase macrophenocryst crystallisation obtained from Linkam^® heating stage experiments, and from glass inclusion compositions corrected for post-entrapment crystallisation, give temperatures up to 1260°C, corresponding to crystallisation at middle to deep crustal levels. Temperature differences of less than 100°C between plagioclase-hosted glass inclusions before and after post-entrapment plagioclase crystallisation show that the macrophenocrysts must have been kept at elevated temperatures prior to incorporation in their present host magmas. We suggest that the macrophenocrysts of the plagioclase ultraphyric basalts accumulated in crystal mush bodies underneath the rift zone and were picked up by their present hosts during a rifting event with increased magma supply from the mantle.  相似文献   

Thermal water prospecting results at Jelenia Góra-Cieplice (Sudetes, Poland) versus geothermometric forecasts     

J. Dowgiałło 《Environmental Geology》2000,39(5):433-436

 To provide additional volume of thermal water for balneotherapy and space heating the well Cieplice-1 has been deepened from 661 m to 2002.5 m. A spontaneous outflow of water with temperatures reaching 87.8  °C was obtained. Thermal logging revealed 97.7  °C at 1870 m. These results are consistent with earlier estimates based on various chemical geothermometers that indicated water temperatures in the lower parts of the geothermal system possibly exceeding 100  °C. This was also confirmed by the cationic composition geothermometer. The estimates based on the dependence of saturation indices on temperature did not prove correct, suggesting 65  °C as the most probable maximum temperature of the water. Received: 11 Sebtember 1998 · Accepted: 7 January 1999  相似文献   

IMPACT OF SUBGLACIAL GEOTHERMAL ACTIVITY ON MELTWATER QUALITY IN THE JÖKULSÁ Á SÓLHEIMASANDI SYSTEM,SOUTHERN ICELAND     

D. M. LAWLER  H. BJ RNSSON  M. DOLAN 《水文研究》1996,10(4):557-577

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