Mineralogic and Oxygen Isotopic Studies of Open System Magmatie Processes in the South Kawishiwi Intrusion, Spruce Road Area, Duluth Complex, Minnesota     

LEE  INSUNG; RIPLEY  EDWARD M. 《Journal of Petrology》1996,37(6):1437-1461

The South Kawishiwi intrusion, located along the western marginof the Duluth Complex, Minnesota, is one of several compositeintrusions that are found in the Complex. The Duluth Complexis the principal exposed plutonic portion of the 1.1 Ga MidcontineniRift system. In the Spruce Road area the South Kawishiwi intrusionis divided into seven distinct units that are part of the broaderSouth Kawishiwi Troctolite Series defined by Severson (Tech.Rep. NRRI/TR-91/13a, Natural Resources Research Institute, Universityof Minnesota, Duluth, 1994). Units may be characterized as follows:Unit I—basal accumulation of heterogeneous gabbro, troctolite,and norite; Unit II—norite with abundant inverted pigeonite;Unit III—troctolite and olivine gabbro with local oxide-richlayers; Unit IV—mlatroctolite, troctolite, olivine gabbro;Unit VI—increased plagioclase abundance in troctolitesand leucocratic troctolites; Unit VI—strongly alteredtroctolite; Unit VII—similar to Unit V, troctolite andleucocratic troctolite. Country rocks in the Spruce Road areaare granodiorite to quartz monzonite of the Archean Giants RangeBatholith. Sutfide mineralization, consisting of 1–5 vol.% of disseminated pyrrhotitt, cubanite, chalcopyrite and pentlandite,occurs in Units I, II, III, and VI. Oxygen isotopic analysesindicate that Unit II has experienced extensive crustal contamination.¹⁸O values of Unit II range from 6.9 to 7.1% and are ¹⁸O enrichedcompared with values of 5.1–6.8% found in other units.Silica contamination is indicated based not only on ¹⁸O values,but also by the predominance of orthopyroxene in the unit. Possiblehigh-¹⁸O contaminant rocks include the Giants Range Batholithand pelitic rocks of the Lower Proterozoic Virginia Formationor Biwabik Iron Formation. Mass balance computations suggestthat units in the Spruce Road area may be related through varyingdegrees of fractionation of a high-Al, olivine tholeiite magma.Modeling of trace element concentrations and variations in mineralchemistry suggest that discontinuities within the major unitsdeveloped by in situ boundary-layer equilibrium crystallizationof solidification zones 20–50 m in thickness, followedby recharge of fresh magma. Upward enrichment of incompatibleelements, olivine Fa content, and plagioclase Ab content maybe effectively explained by this process. ¹⁸O values of uncontaminatedrock types are strongly correlative with modal mineralogy, andcan also be modeled by boundary-layer fractionation, A parentalmagma ¹⁸ O value of 6.3% is calculated for Unit VII based onolivine and plagioclase values, and is similar to that of severalother large, layered mafic intrusives. KEY WORDS: Duluth Complex; South Kawishiwi Intrusion; high-Al olivine tholeiite; open system crystallization; oxygen isotopes ^* Present address: Korea Basic Science Center, Isotope Research Group, Yeocun Dong 224–1, Yusung Ku, Yusung P.O. Box 41, Taejean 305–333, Korea  相似文献   

Near-solidus Melting of the Shallow Upper Mantle: Partial Melting Experiments on Depleted Peridotite   总被引：10，自引：5，他引：10  

WASYLENKI  LAURA E.; BAKER  MICHAEL B.; KENT  ADAM J. R.; STOLPER  EDWARD M. 《Journal of Petrology》2003,44(7):1163-1191

We present the results of melting experiments on a moderatelydepleted peridotite composition (DMM1) at 10 kbar and 1250–1390°C.Specially designed experiments demonstrate that liquids extractedinto aggregates of vitreous carbon spheres maintained chemicalcontact with the bulk charge down to melt fractions of  相似文献   

Subaquatic flow tills: a new interpretation for the genesis of some laminated till deposits     

EDWARD B. EVENSON  ALEKSIS DREIMANIS  JOHAIL W. NEWSOME 《Boreas: An International Journal of Quaternary Research》1977,6(2):115-133

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COMMENTS ON “AN INTERPRETATION SYSTEM FOR GEO-ELECTRICAL SOUNDING GRAPHS”*     

EDWARD SZARANIEC 《Geophysical Prospecting》1974,22(1):189-190

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On the meltwater genesis of drumlins   总被引：1，自引：0，他引：1  

EDWARD M. SHOEMAKER 《Boreas: An International Journal of Quaternary Research》1995,24(1):3-10

Large subglacial cavities in basal ice. the presumed precursors of depositional drumlins, can be created by corrasion from suspended sediment during a large water sheet outburst flood. The cavities are primarily the result of vortex action. For a given flood discharge the corrasion rate of the ice roof increases with water sheet velocity, V, to a power greater than V^16/3, Because of ice displacment during a flood, V can vary spatially along a flow line by up to an order of magnitude. The highest velocities normally occur downstream from major bed depressions or near the ice margin. Fields of large drumlins frequently occur at such sites. The process of formation of large subglacial cavities is predicted to be more velocity-sensitive than the erosion of bedrock. No accurate estimate of water sheet flood volumes can be made at this time but they could be at least an order of magnitude less than the 80 000 km³, which was previously estimated.  相似文献   

Petrology of Biotite-Cordierite-Garnet Gneiss of the McCullough Range, Nevada II. P-T-aH2O Path and Growth of Cordierite During Late Stages of Low-P Granulite-Grade Metamorphism     

YOUNG  EDWARD D. 《Journal of Petrology》1989,30(1):61-78

Thermodynamic calculations based on addition of mass balanceequations to the Gibbs Method (Spear, 1986) are used to modelthe cordierite-producing reaction in pelitic gneiss from theMcCullough Range, southern Nevada. Calculations which treatthe model paragenesis as a system open to transfer of H₂O areconsistent with textural relations. Results indicate that cordieritegrew by the continuous net-transfer reaction: 0?76 BIO+1?72 SILL+3? 55 QTZ+0?27 PLG+0?005 GRT +0?06Al₂R²⁺_–1Si_–1[BIO]1?02 KSP+0?76 H₂O +0?30 FeMg_–1[CRD]+0?15FeMg_–1[BIO]+0?0005 FeMg_–1[GRT] +0?005 CaNaAl_–1Si_–1[PLG] with decreasing P, decreasing T, and increasing a_H2O The steepretrograde dP/dT path for these low-pressure granulites contrastswith isobaric cooling paths typical of higher pressure granulites,and suggests uplift and erosion were active during Proterozoicgranulite-grade metamorphism in this area.  相似文献   

The geometry and organization of fluviodeltaic channel sandstones in the Jurassic Saltwick Formation, Yorkshire, England     

RUNE MJØS  EDWARD PRESTHOLM 《Sedimentology》1993,40(5):919-935

Within the Middle Jurassic Saltwick Formation of Yorkshire, England, 65% of the fluvial channel sandstones (n= 22) have width to thickness ratios in the range 17–30. More than 90% lie in the range 17–67 and are classified as narrow sheet channel sandstones. A broad sheet channel sandstone (c. 15 m thick, 3 km wide, width to thickness ratio of 200) occurs at the base of the formation in the proximal part of the studied depositional system. The thicknesses of the channel sandstones are in the range 4 m to more than 22 m, with 90% in the range 4–12 m. The widths of the channel sandstone sections are in the range 100–800 m, with 80% between 100 and 400 m. In plan view the channel sandstones display relatively constant thicknesses across the main part (80%) of the channel body. Channel sandstones are usually multistorey. The storeys are separated by major scour surfaces, with depths of scour ranging from 2 m to 8–10 m. The individual storeys are 4–13 m thick, and transverse and oblique storey sections have lateral extents of 60–480 m. Vertical stacking of storeys is accompanied by a decrease in the width to thickness ratio of the channel sandstones, whereas lateral stacking of storeys is accompanied by an increase. Mudstones and siltstones within channel sandstone bodies occur at the top of storeys and were in most cases deposited during channel abandonment. The Saltwick Formation was deposited during increasing accommodation forming a transgressive systems tract. The channel sandstone to interchannel sediment ratio is highest in the lower parts of the transgressive systems tract. The quantitative geometry and architecture data from the Saltwick Formation may be useful for describing and modelling humid delta plain hydrocarbon reservoirs of transgressive systems tracts.  相似文献   

A look at some details of the growth of initial uncertainties     

EDWARD N. LORENZ 《地球，A辑:动力气象学与海洋学》2005,57(1):1-11

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The general circulation of the atmosphere: an evolving problem     

EDWARD N. LORENZ 《地球，A辑:动力气象学与海洋学》1991,43(4):8-15

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The general circulation of the atmosphere: an evolving problem     

EDWARD N. LORENZ 《Tellus. Series B, Chemical and physical meteorology》1991,43(4):8-15

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