Geochemistry and Intrusive History of the Ashland Pluton, Klamath Mountains, California and Oregon   总被引：3，自引：1，他引：2  

GRIBBLE  ROBERT F.; BARNES  CALVIN G.; DONATO  MARY M.; HOOVER  JAMES D.; KISTLER  RONALD W. 《Journal of Petrology》1990,31(4):883-923

The Ashland pluton is a calc-alkaline plutonic complex thatintruded the western Paleozoic and Triassic belt of the KlamathMountains in late Middle Jurassic time. The pluton comprisesa series of compositionally distinct magma pulses. The oldestrocks are hornblende gabbro and two-pyroxene quartz gabbro withinitial ⁸⁷Sr/⁸⁶Sr = 0{dot}7044, ¹⁸O = 8{dot}7%, and REE patternswith chondrite normalized La/Lu = 7. These units were followedby a suite of tonalitic rocks (La_N/Lu_N = 7) and then by a suiteof K₂O- and P₂O₅ rocks of quartz monzodioritic affinity (La_N/Lu_N= 13–21; La_N/Sm_N = 2{dot}4–3{dot}) The quartz monzodioriticrocks were then intruded by biotite granodiorite and granitewith lower REE abundances but more fractionated LREE(La_N/Lu_N= 13–19; La_N/Sm_N = 4{dot}3–6 and they, in turn,were host to dikes and bosses of hornblende diorite. The latestintrusive activity consisted of aplitic and granitic dikes.Combined phase equilibria and mineral composition data, indicateemplacement conditions of approximately P_total = 2{dot}3kb,P_H2O between 1{dot}5 and 2{dot}2 kb, and f_O2 between the nickel-nickeloxide and hematite-magnetite buffers. Successive pulses of magma display increasing SiO₂ togetherwith increasing ¹⁸O and decreasing initial ⁸⁷Sr/⁸⁶Sr. The isotopicdata are consistent with either (1) combined fractional crystallizationof andesitic magma and concurrent assimilation of crustal materialcharacterized by low Sr₁ and high (¹⁸O or, more probably, (2)a series of partial melting events in which sources were successivelyless radiogenic but richer in ¹⁸O Each intrusive stage displaysevidence for some degree of crystal accumulation and/or fractionalcrystallization but neither process adequately accounts fortheir compositional differences. Consequently, each stage appearsto represent a distinct partial melting or assimilation event. The P₂O₅-rich nature of the quartz monzodiorite suite suggestsaccumulation of apatite. However, the suite contains abundantmafic microgranitoid enclaves and most apatite in the suiteis acicular. These observations suggest that magma mixing affectedthe compositional variation of the quartz monzodiorite suite.Mass balance calculations are consistent with a simple mixingprocess in which P₂O₅-rich alkalic basalt magma (representedby the mafic microgranitoid enclaves) was combined with a crystal-poorfelsic magma (represented by the tonalite suite), yielding aquartz monzodioritic magma that then underwent differentiationby crystal fractionation and accumulation.  相似文献   

EFFECT OF SNOW FENCE HEIGHT ON WIND SPEED     

RONALD D. TABLER  DONALD L. VEAL 《水文科学杂志》2013,58(4):49-56

Abstract

Accumulations of snow behind fences may increase the water yield in windswept areas. The efficiency of snow collection depends on the reduction in wind speed in the lee of the fence. Wind speeds have been measured to windward and to leeward of vertical slat fences from 6 to 16 ft. high. The down-wind measurements were made at distances of 2.5H, 5H and 10H from the fence where H is the height of the fence. Speed measurements at various levels were integrated up to the height of the fence and the percentage reduction in wind speed was calculated. Expressions are given for the velocity reduction factor at distances down-wind of fences having a bottom gap, and for the cross-sectional area of a fully developed drift.  相似文献   

Erg deposits in the Lower Jurassic Wingate Sandstone, northeastern Arizona: oblique dune sedimentation     

LARS B. CLEMMENSEN  RONALD C. BLAKEY 《Sedimentology》1989,36(3):449-470

The Lower Jurassic erg (aeolian sand sea) deposits of the Wingate Sandstone on the Colorado Plateau are beautifully exposed near Many Farms, Arizona. These 3-D outcrops allow a detailed study of structures and sequenses in the erg body. The erg sequence comprises chiefly oblique dune deposits. The dune facies are in most cases characterized by a well-developed tripartite upbuilding. Each dune coset contains unusually thick and intricate bottomsets, medial low-angle dipping toesets, and upper steeply dipping foresets. The foresets reveal significant across-crest transport of sand and dip within a narrow range of directions towards the ESE. The bottomset beds are composed of compound cross-bedding that documents strong along-crest transport towards the SSW, whereas the toeset beds reveal upslope, downslope, and along-crest transport of sand. The ancient dunes apparently formed in a directionally varying wind flow with prevailing winds (early summer) from the NW and periodic strong winds (late summer) from the SW. The dunes were oblique not only to seasonal transport directions, but also to the resultant annual transport direction and dune migration direction. This was caused by the interaction of the dune system with the primary winds which resulted in secondary airflow and significant along-crest transport of sand. The erg deposits at Many Farms are separated by a number of super bounding surfaces suggesting several episodes of erg formation and destruction. The initial erg system was dominated by transverse dunes, but overlying ergs only contained oblique dunes. All erg systems were bounded to the SW by wide regions of erg margin environments in which aeolian sand sheet, fluvial, and lacustrine facies were deposited. Even though fluvial deposits are absent from the main part of the sequence at the study area, the effects of this system are reflected within the erg deposits at Many Farms.  相似文献   

Contact Metamorphism of Serpentinite, Chloritic Blackwall and Rodingite at Paddy-Go-Easy Pass, Central Cascades, Washington   总被引：2，自引：2，他引：2  

FROST  B. RONALD 《Journal of Petrology》1975,16(1):272-313

The 2 km wide contact aureole produced from serpentinite bythe intrusion of the Mount Stuart Batholith into the IngallsComplex at Paddy-Go-Easy Pass contains the following ultramaficassemblages, in order of increasing grade: serpentine-forsterite-diopside,serpentine-forsterite-tremolite, forsterite-talc, forsterite-anthophyllite,forsterite-enstatite-anthophyllite, forsterite-enstatite-chlorite,forsterite-enstatite-spinel. Associated metarodingites displayfive metamorphic zones, the diagnostic assemblages of whichare, in increasing grade: grossular-idocrase-chlorite, grossular-diopside-chlorite,epidote-diopside-chlorite, epidote-diopside-spinel, plagioclase-grossular-diopside.Mafic hornfels in the aureole contains no orthopyroxene, indicatingthat the conditions of pyroxene hornfels facies were not reached. The breakdown of chlorite is best displayed in aluminous blackwallreaction zones around mafic inclusions in the peridotite. Attemperatures above those of the anthophyllite-out isograd, butwithin the field of forsterite+tremolite, these chlorite-richrocks react to form the assemblage: forsterite-enstatite-spinel.Calculations show that cordierite did not form as a result ofchlorite breakdown in the natural system because impurities,such as iron and chromium, displaced the equilibrium: forsterite+cordierite=enstatite+spinelto much lower pressures than the three kilobars found in thepure system. The primary chromite of the peridotite has been altered to chrome-magnetitein the serpentinite. This alteration seems to be isochemicalover the whole rock, as true chromite, formed by metamorphism,occurs at grades above that of the forsterite-enstatite-anthophylliteassemblage. Calcic amphibole in high-grade metaperidotite is tremolite,even in the presence of aluminous chromite, whereas that inmetamorphosed blackwall rock grades from tremolite into hornblende.The pattern of substitution appears to be: Mg₂Si₃(Na,K)(Al^VI)₂(Al^IV)₃.  相似文献   

The rôle of thermohaline circulation in climate     

SYUKURO MANABE  RONALD J. STOUFFER 《Tellus. Series B, Chemical and physical meteorology》1999,51(1):91-109

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Notes on the appropriateness of "bred modes" for generating initial perturbations used in ensemble prediction     

BY RONALD M. ERRICO    ROLF LANGLAND 《地球，A辑:动力气象学与海洋学》1999,51(3):431-441

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Are two modes of thermohaline circulation stable?     

BY SYUKURO MANABE  RONALD J. STOUFFER 《地球，A辑:动力气象学与海洋学》1999,51(3):400-411

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Water vapour ¹⁸O/¹⁶O isotope ratio in surface air in New England, USA     

XUHUI LEE  RONALD SMITH  JOHN WILLIAMS 《Tellus. Series B, Chemical and physical meteorology》2006,58(4):293-304

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Linearization and adjoint of parameterized moist diabatic processes     

TOMISLAVA VUKI&#;EVI&#;  RONALD M. ERRICO 《地球，A辑:动力气象学与海洋学》1993,45(5):493-510

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Gould Pond, Maine: late-glacial transitions from marine to upland environments     

R. SCOTT ANDERSON  GEORGE L. JACOBSON JR.    RONALD B. DAVIS  ROBERT STUCKENRATH 《Boreas: An International Journal of Quaternary Research》1992,21(4):359-371

Gould Pond sediments are unusual in North America in that they include a continuous record of change from marine to freshwater conditions during the late-glacial period, with a wide array of micro- and macrofossils deposited during a period of high sedimentation rate. Marine waters, much colder than those in the present Gulf of Maine, covered the site at the time of deglaciation (c. 13,200 BP). Plants characteristic of modem tundra grew on nearby uplands. Marine recession, due to isostatic rebound of the land, occurred from c . 12,800–12,200 BP. The lake water was completely freshened by 12,000 BP. A sparse shrub-herb tundra became established around Gould Pond as marine waters receded. Subsequent to 11,300 BP, sedges and other herbs became more abundant, and willow and Dryas less abundant, signifying increased warmth and decreased frost action. At least six tree species, all now common in the area, arrived around Gould Pond between c . 10,800 and 10,500 BP. This rapid transition was coincident with the most rapid major non-anthropogenic change of vegetation at sites across eastern North America during the postglacial period.  相似文献