ATLAS OF METAMORPHIC–METASOMATIC TEXTURES AND PROCESSES     

R. Vernon 《Journal of Metamorphic Geology》1992,10(3):483-485

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Nd,Sr, and Pb isotopic characteristics of Cretaceous intrusive rocks from deep levels of the Sierra Nevada batholith,Tehachapi Mountains,California   总被引：6，自引：0，他引：6  

David A. Pickett  Jason B. Saleeby 《Contributions to Mineralogy and Petrology》1994,118(2):198-215

The Cretaceous gabbroic to granitic intrusive rocks of the Tehachapi Mountains were emplaced at depths of 25–30 km and thus afford a view of deep processes in the Sierra Nevada batholith. They consist of the 115 Ma Tehachapi suite and the 100 Ma Bear Valley suite; new zircon U-Pb age data reveal the presence of the latter as far west as Grapevine Canyon. The Nd, Sr, Pb, and O isotopic whole-rock data and zircon Pb inheritance patterns for the bulk of the suites suggest an origin by mixing between depleted mantlederived magmas and metasedimentary material with a substantial component of old continental material. However, this mixing is not evident in variations between isotopic ratios and chemical and lithologic parameters. This implies that isotopic hybridization of magmas took place deeper than 30 km, and that fractionation processes are likely responsible for the bulk of the chemical variation in this part of the Sierra Nevada batholith. Consideration of the isotopic data in the context of the Sierra Nevada batholith as a whole suggests that the well-known east-to-west isotopic gradients in the batholith may reflect a change in the average isotopic character of the preintrusive frame-work rather than a change in amount of crustal component. On the other hand, the lack of areal gradients in Sr and Nd isotopic ratios in the main study area may indicate a lack of pronounced gradation at deep levels, at least within the western batholith.  相似文献   

The Port Mouton Shear Zone: intersection of a regional fault with a crystallizing granitoid pluton   总被引：2，自引：0，他引：2  

D. Barrie Clarke  Krista L. McCuish  Ron H. Vernon  Victor Maksaev  Brent V. Miller   《Lithos》2002,61(3-4):141-159

The peraluminous tonalite–monzogranite Port Mouton Pluton is a petrological, geochemical, structural, and geochronological anomaly among the many Late Devonian granitoid intrusions of the Meguma Lithotectonic Zone of southern Nova Scotia. The most remarkable structural feature of this pluton is a 4-km-wide zone of strongly foliated (040/subvertical) monzogranites culminating in a narrow (10–30 m), straight, zone of compositionally banded rocks that extends for at least 3 km along strike. The banded monzogranites consist of alternating melanocratic and leucocratic compositions that are complementary to the overall composition of that part of the pluton, suggesting an origin by mineral–melt and mineral–mineral sorting. Biotite and feldspar are strongly foliated in the plane of the compositional bands. These compositional variations and foliations originated by a process of segregation flow during shearing of the main magma with a crystallinity of 55–75%. Subsequent minor brittle fracturing of feldspars, twinning of microcline, development of blocky sub-grains in quartz, and kinking of micas demonstrate overprinting by a high-temperature deformation straddling the monzogranite solidus. Small folds and late sigmoidal dykes indicate dextral movement on the shear zone. This Port Mouton Shear Zone (PMSZ) is approximately co-linear with the only outcrops of Late Devonian mafic intrusions in the area, two of which are syn-plutonic with well-developed mingling textures in the marginal tonalite of the Port Mouton Pluton. Also closely co-linear with the mafic intrusions are a granitoid dyke that extends well beyond the outer contact of the Port Mouton Pluton, a swarm of large aligned angular xenolithic slabs, a zone of thin wispy schlieren banding, a large Be-bearing pegmatite, and a breccia pipe with abundant garnetiferous metapelitic xenoliths. In various ways, the shear zone may control all of these features. The Port Mouton Shear Zone is parallel to many other NE-trending faults and shear zones in the northern Appalachians, probably related to the docking of the Meguma Zone along the Cobequid–Chedabucto Fault system.  相似文献   

Sediment deposition in the flood plain of Stemple Creek Watershed, northern California     

Jerry C. Ritchie  Vernon L. Finney  Kenneth J. Oster  Carole A. Ritchie 《Geomorphology》2004,61(3-4):347-360

Over the past 150 years, major land use changes have occurred in the Stemple Creek Watershed in northern California that have caused erosion to move soils from the upland to the flood plain, stream channels, and the bay. The purpose of this study is to document the recent (1954 to present) sediment deposition patterns in the flood plain area adjacent to Stemple Creek using the ¹³⁷Cesium technique. Sediment deposition ranged from 0.26 to 1.84 cm year⁻¹ for the period from 1964 to 2002 with an average of 0.85±0.41 cm year⁻¹. Sediment deposition rates were higher for the 1954 to 1964 period with a range of 0.31–3.50 cm year⁻¹ and an average of 1.29±1.04 cm year⁻¹. These data indicate that sediment deposition in the flood plain has decreased since the middle 1950s, probably related to reduction in row crop agriculture and an increase in pasturelands. This study shows that the flood plains in the Stemple Creek Watershed are a significant sink for the soils being eroded from the upland area. Given the significance of the flood plain for trapping eroded materials before they reach the stream channels or the bay, efforts need to be made to manage these flood plain areas to insure that they do not change and become a source rather than a sink for eroded materials as improved management practices on the upland areas reduce sediment input to the flood plain.  相似文献   

Magnetosheath Interaction with the High Latitude Magnetopause     

S. Savin  A. Skalsky  L. Zelenyi  L. Avanov  N. Borodkova  S. Klimov  V. Lutsenko  E. Panov  S. Romanov  V. Smirnov  YU. Yermolaev  P. Song  E. Amata  G. Consolini  T. A. Fritz  J. Buechner  B. Nikutowski  J. Blecki  C. Farrugia  N. Maynard  J. Pickett  J. A. Sauvaud  J. L. Rauch  J. G. Trotignon  Y. Khotyaintsev  K. Stasiewicz 《Surveys in Geophysics》2005,26(1-3):95-133

We present both statistical and case studies of magnetosheath interaction with the high-latitude magnetopause on the basis of Interball-1 and other ISTP spacecraft data. We discuss those data along with recently published results on the topology of cusp-magnetosheath transition and the roles of nonlinear disturbances in mass and energy transfer across the high-latitude magnetopause. For sunward dipole tilts, a cusp throat is magnetically open for direct interaction with the incident flow that results in the creation of a turbulent boundary layer (TBL) over an indented magnetopause and downstream of the cusp. For antisunward tilts, the cusp throat is closed by a smooth magnetopause; demagnetized ‘plasma balls’ (with scale ∼ few R_E, an occurrence rate of ∼25% and trapped energetic particles) present a major magnetosheath plasma channel just inside the cusp. The flow interacts with the ‘plasma balls’ via reflected waves, which trigger a chaotization of up to 40% of the upstream kinetic energy. These waves propagate upstream of the TBL and initiate amplification of the existing magnetosheath waves and their cascade-like decays during downstream passage throughout the TBL. The most striking feature of the nonlinear interaction is the appearance of magnetosonic jets, accelerated up to an Alfvenic Mach number of 3. The characteristic impulsive local momentum loss is followed by decelerated Alfvenic flows and modulated by the TBL waves; momentum balance is conserved only on time scales of the Alfvenic flows (1/f_A ∼12 min). Wave trains at f_A∼1.3 mHz are capable of synchronizing interactions throughout the outer and inner boundary layers. The sonic/Alfvenic flows, bounded by current sheets, control the TBL spectral shape and result in non-Gaussian statistical characteristics of the disturbances, indicating the fluctuation intermittency. We suggest that the multi-scale TBL processes play at least a comparable role to that of macro-reconnection (remote from or in the cusp) in solar wind energy transformation and population of the magnetosphere by the magnetosheath plasma. Secondary micro-reconnection constitutes a necessary chain at the small-scale (∼ion gyroradius) edge of the TBL cascades. The thick TBL transforms the flow energy, including deceleration and heating of the flow in the open throat, ‘plasma ball’ and the region downstream of the cusp.  相似文献   

Shallow seismic trapping structure in the San Jacinto fault zone near Anza, California   总被引：3，自引：0，他引：3  

M. A. Lewis  Z. Peng †  Y. Ben-Zion  F. L. Vernon 《Geophysical Journal International》2005,162(3):867-881

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Testing the Limits of ICP-MS: Determination of Trace Elements in Ground Water at the Part-Per-Trillion Level   总被引：3，自引：0，他引：3  

Klaus J. Stetzenbach  Megumi Amano  David K. Kreamer  Vernon F. Hodge 《Ground water》1994,32(6):976-985

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3-D velocity structure of the San Jacinto fault zone near Anza, California—I. P waves     

Jennifer S. Scott  T. Guy Masters  Frank L. Vernon 《Geophysical Journal International》1994,119(2):611-626

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Book reviews     

Yukio Fujinawa  A. V. Koloskov  Gerardo G. Tango  Lech Stefaníak  Douglas R. Schmitt  Kei Katsumata  Vernon F. Cormier  Wladislaw Lyatsky  Krzysztof Haman  P. Vincent  Konrad Bajer  Henryk Piwkowski 《Pure and Applied Geophysics》1991,136(2-3):343-367

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Lower Tropospheric Warm Air Advection Patterns Associated with Heavy Rainfall over the Appalachian Region*     

Charles E. Konrad  Vernon Meentemeyer 《The Professional geographer》1994,46(2):143-155

A synoptic climatology of warm season heavy rainfall is developed from patterns of 850 mb thermal advection over the Appalachian region. Heavy rain events are categorized according to the position and orientation of a warm air advection (WAA) ridge, a feature found in nearly two-thirds of the events. Numerous study events occur within the conditionally unstable region of the WAA ridge. In fact, numerous occurrences of heavy rainfall are tied to a superpositioning of a WAA and air mass instability ridge in the vicinity or upstream of the heavy rain area.  相似文献