Are extrusive rhyolites produced from permeable foam eruptions?     

I. Friedman 《Bulletin of Volcanology》1989,51(1):69-71

The permeable foam hypothesis is suggested by Eichelberger et al. (1986) to explain a major loss of water from rhyolitic magmas in the volcanic conduit. Evidence for the high-water content of the major portion of the magma is herein examined and rejected. Eichelberger's hypothesis does not take into account the large (2 orders of magnitude) viscosity change that would occur in the conduit as a result of water loss. It also requires that the permeable foam collapse and weld to form an obsidian that in thin section displays no evidence of the foam. An alternate hypothesis to explain the existence of small amounts of high water content rhyolite glasses in acid volcanoes is that rhyolite magmas are relatively dry (0.1–0.3% H₂O) and that water enters the magma from the environment to produce a water-rich selvage which then is kneaded into the body of the magma.  相似文献   

Centroid-moment tensor solutions for January–March, 1983     

A.M. Dziewonski  A. Friedman  J.H. Woodhouse 《Physics of the Earth and Planetary Interiors》1983,33(2):71-75

Centroid-moment tensor solutions are presented for 89 earthquakes that occurred during the first quarter of 1983.  相似文献   

Magmatic relationships and ages of Caribbean Island arc tholeiites, boninites and related felsic rocks, Dominican Republic     

J. Escuder Viruete  A. Díaz de Neira  P.P. Herniz Huerta  J. Monthel  J. García Senz  M. Joubert  E. Lopera  T. Ullrich  R. Friedman  J. Mortensen  A. Prez-Estaún 《Lithos》2006,90(3-4):161-186

Located in the Cordillera Oriental of the Dominican Republic, the Early Cretaceous Los Ranchos Fm (LRF) comprises a > 3-km thick sequence of volcanic and volcaniclastic rocks with variable geochemical characteristics, which is intruded by tonalite batholiths, minor gabbro/diorite plutons and mafic dykes. From top to bottom, three main stratigraphic units have been mapped: upper basaltic, intermediate rhyodacitic and lower basaltic. Combined detailed mapping, stratigraphy, geochemistry, Rb–Sr/Sm–Nd isotopic studies and U–Pb/Ar–Ar geochronology show that the mafic rocks of the LRF include boninites and LREE-depleted island arc tholeiites (IAT) in the lower unit, both which appear genetically related, whereas normal IAT occur in the upper unit. The source for these rocks is thought to reflect variably depleted mantle, overprinted by a subduction zone component. Contemporaneous Aptian U–Pb zircon ages were obtained for a rhyodacite from the intermediate unit (116.0 ± 0.8 Ma) and a tonalite of the Zambrana batholith (115.5 ± 0.3 Ma) that intrudes the LRF. The similarity of trace element signatures in both units argues for genetic link between the felsic volcanics of the LRF and the tonalite plutonism. Low-K rhyolites and tonalite batholiths are interpreted as products of secondary melting at the base of thickened early arc crust. ⁴⁰Ar/³⁹Ar plateau ages of hornblende in most tonalites are Albian (109–106 Ma) and interpreted as final cooling ages, prior to unroofing and growth of unconformable overlying reef limestones of the Hatillo Fm (112–100 Ma). The LREE-depleted IAT and boninites of lower basaltic unit are interpreted to have formed during subduction zone initiation in the Caribbean Island arc, and the normal IAT of the upper unit are thought to represent the subsequent establishment of the volcanic front.  相似文献   

Observations of eruption clouds from Sakura-zima volcano,Kyushu, Japan from Skylab 4     

Jules D. Friedman  Grant Heiken  Darryl Randerson  David S. McKay 《Journal of Volcanology and Geothermal Research》1976,1(4):305-329

Hasselblad and Nikon stereographic photographs taken from Skylab between 9 June 1973 and 1 February 1974 give synoptic plan views of several entire eruption clouds emanating from Sakura-zima volcano in Kagoshima Bay, Kyushu, Japan. Analytical plots of these stereographic pairs, studied in combination with meteorological data, indicate that the eruption clouds did not penetrate the tropopause and thus did not create a stratospheric dust veil of long residence time. A horizontal eddy diffusivity of the order of 10⁶ cm² s^?1 and a vertical eddy diffusivity of the order of 10⁵ cm² s^?1 were calculated from the observed plume dimensions and from available meteorological data. These observations are the first, direct evidence that explosive eruption at an estimated energy level of about 10¹⁸ ergs per paroxysm may be too small under atmospheric conditions similar to those prevailing over Sakura-zima for volcanic effluents to penetrate low-level tropospheric temperature inversions and, consequently, the tropopause over northern middle latitudes. Maximum elevation of the volcanic clouds was determined to be 3.4 km. The cumulative thermal energy release in the rise of volcanic plumes for 385 observed explosive eruptions was estimated to be 10²⁰ to 10²¹ ergs (10¹³ to 10¹⁴ J), but the entire thermal energy release associated with pyroclastic activity may be of the order of 2.5 × 10²² ergs (2.5 × 10¹⁵ J).Estimation of the kinetic energy component of explosive eruptions via satellite observation and meteorological consideration of eruption clouds is thus useful in volcanology as an alternative technique to confirm the kinetic energy estimates made by ground-based geological and geophysical methods, and to aid in construction of physical models of potential and historical tephra-fallout sectors with implications for volcano-hazard prediction.  相似文献   

Caribbean island-arc rifting and back-arc basin development in the Late Cretaceous: Geochemical, isotopic and geochronological evidence from Central Hispaniola     

J. Escuder Viruete  M. Joubert  P. Urien  R. Friedman  D. Weis  T. Ullrich  A. Prez-Estaún 《Lithos》2008,104(1-4):378-404

We present new regional petrologic, geochemical, Sr–Nd isotopic, and U–Pb geochronological data on the Turonian–Campanian mafic igneous rocks of Central Hispaniola that provide important clues on the development of the Caribbean island-arc. Central Hispaniola is made up of three main tectonic blocks—Jicomé, Jarabacoa and Bonao—that include four broad geochemical groups of Late Cretaceous mafic igneous rocks: group I, tholeiitic to calc-alkaline basalts and andesites; group II, low-Ti high-Mg andesites and basalts; group III, tholeiitic basalts and gabbros/dolerites; and group IV, tholeiitic to transitional and alkalic basalts. These igneous rocks show significant differences in time and space, from arc-like to non-arc-like characteristics, suggesting that they were derived from different mantle sources. We interpret these groups as the record of Caribbean arc-rifting and back-arc basin development in the Late Cretaceous. The> 90 Ma group I volcanic rocks and associated cumulate complexes preserved in the Jicomé and Jarabacoa blocks represent the Albian to Cenomanian Caribbean island-arc material. The arc rift stage magmatism in these blocks took place during the deposition of the Restauración Formation from the Turonian–Coniacian transition (~ 90 Ma) to Santonian/Lower Campanian, particularly in its lower part with extrusion at 90–88 Ma of group II low-Ti, high-Mg andesites/basalts. During this time or slightly afterwards adakitic rhyolites erupted in the Jarabacoa block. Group III tholeiitic lavas represent the initiation of Coniacian–Lower Campanian back-arc spreading. In the Bonao block, this stage is represented by back-arc basin-like basalts, gabbros and dolerite/diorite dykes intruded into the Loma Caribe peridotite, as well as the Peralvillo Sur Formation basalts, capped by tuffs, shales and Campanian cherts. This dismembered ophiolitic stratigraphy indicates that the Bonao block is a fragment of an ensimatic back-arc basin. In the Jicomé and Jarabacoa blocks, the mainly Campanian group IV basalts of the Peña Blanca, Siete Cabezas and Pelona–Pico Duarte Formation, represent the subsequent stage of back-arc spreading and off-axis non-arc-like magmatism, caused by migration of the arc toward the northeast. These basalts have geochemical affinities with the mantle domain influenced by the Caribbean plume, suggesting that mantle was flowing toward the NE, beneath the extended Caribbean island-arc, in response to rollback of the subducting proto-Caribbean slab.  相似文献   

North Atlantic extratropical and subpolar gyre variability during the last 120 years: a gridded dataset of surface temperature,salinity, and density. Part 1: dataset validation and RMS variability     

Reverdin  Gilles  Friedman  Andrew Ronald  Chafik  Léon  Holliday  Naomi Penny  Szekely  Tanguy  Valdimarsson  Héðinn  Yashayaev  Igor 《Ocean Dynamics》2019,69(3):385-403

We present a binned annual product (BINS) of sea surface temperature (SST), sea surface salinity (SSS), and sea surface density (SSD) observations for 1896–2015 of the subpolar North Atlantic between 40° N and 70° N, mostly excluding the shelf areas. The product of bin averages over spatial scales on the order of 200 to 500 km, reproducing most of the interannual variability in different time series covering at least the last three decades or of the along-track ship monitoring. Comparisons with other SSS and SST gridded products available since 1950 suggest that BINS captures the large decadal to multidecadal variability. Comparison with the HadSST3 SST product since 1896 also indicates that the decadal and multidecadal variability is usually well-reproduced, with small differences in long-term trends or in areas with marginal data coverage in either of the two products. Outside of the Labrador Sea and Greenland margins, interannual variability is rather similar in different seasons. Variability at periods longer than 15 years is a large part of the total interannual variability, both for SST and SSS, except possibly in the south-western part of the domain. Variability in SST and SSS increases towards the west, with the contribution of salinity variability to density dominating that of temperature in the western Atlantic, except close to the Gulf Stream and North Atlantic Current in the southwest area. Weaker variability and larger relative temperature contributions to density changes are found in the eastern part of the gyre and south of Iceland.

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Application of Mössbauer spectroscopy,multidimensional discriminant analysis,and Mahalanobis distance for classification of equilibrated ordinary chondrites     

Marek Wo niak  Jolanta Ga&#x;&#x;zka‐Friedman  Przemys&#x;aw Duda  Martyna Jakubowska  Patrycja Rzepecka  &#x;ukasz Karwowski 《Meteoritics & planetary science》2019,54(8):1828-1839

Mössbauer spectra of equilibrated ordinary chondrites consist of two doublets due to paramagnetic iron present in olivines and pyroxenes and two sextets due to magnetically ordered iron present in metallic phases and troilite. The spectral areas of the different mineralogical phases found by Mössbauer spectroscopy in meteorites are proportional to the number of iron atoms in this mineralogical phase. This property of Mössbauer spectra can be the basis for constructing a method for the classification of ordinary chondrites. This idea was first explored at the Mössbauer Laboratory in Kanpur. This group suggested a qualitative method based on 2‐dimensional plots of Mössbauer spectral areas and thus classified properly some meteorites. We constructed a quantitative method using Mössbauer spectral areas, multidimensional discriminant analysis, and Mahalanobis distance (4M method) to determine the probability of a meteorite to be of type H, L, or LL. Based on 59 Mössbauer spectra, we calculated by the 4M method, S _cluster , the level of similarity of the Goronyo meteorite to the clusters. On the plot of ferrosilite versus fayalite, the point representing Goronyo is located on the border between H and L areas. Calculated by the 4M method, the meteorite Goronyo is 32% similar to type H, 75% to type L, and 11% to type LL. Additional mineralogical analyses suggested that the Goronyo meteorite would be classified as type L, although it was originally reported as type H in the Meteoritical Bulletin Database.  相似文献   

Waters and organic-rich waste near dumping grounds in the New York Bight     

G. M. Friedman  P. K. Mukhopadhyay  A. Moch  M. Ahmed 《International Journal of Coal Geology》2000,43(1-4)

The New York Bight is a sector of the Middle Atlantic continental shelf. The Bight consists of a part of the Atlantic Ocean offshore of the New York and New Jersey metropolitan area. This area includes the most populated coastal setting in North America. The Atlantic shelf and its estuaries are used for waste disposal, dredging, commercial fishing, and recreation; activities that contribute to the contamination of associated bottom sediments. Existing data for toxicants are still inadequate. Improvements in sediment and water quality will require a more detailed knowledge and understanding of sediments and water in the Bight. Eleven coring stations were established in New York Bight. Decreases in pH and Eh both above and below the water/sediment interface are attributed to the activity of anaerobic bacteria. Sulfate reduction is one of the important processes in lowering pH. Low Eh values of up to −443 can be related to sulfate-reducing bacteria. The highest negative Eh generally occurs with the highest organic carbon concentration. Core samples yielded up to 4.00% organic carbon compared to 0.8 to 1.2% in sediments of the natural nearshore environment. Twenty-seven different aliphatic hydrocarbons, fourteen PAHs, five cyclic hydrocarbons, and eight dicarboxylic acids were identified in the Bight pore waters. Sediment located deeper in the Hudson Shelf Valley has a greater abundance of aliphatic hydrocarbons as adsorbed pollution on clay and silt. The presence of dicarboxylic acids leached from plastic came from anthropogenic activities (mostly sewage). PAHs have two sources: coal ash (observed in sediments) and petroleum (part of the sewage, run-offs, and oil spills). The rest of the hydrocarbons have a petroleum or biogenic origin. The high amount of organic carbon may be the result of sewage sludge or originated from natural sources. The main sources of contaminants are dumpsites, emergency releases after heavy rainstorms from sewage-treatment plants, tanker washing, storage transfer spills, run-off, and air-borne pollution. The relatively high accumulation of organic matter causes oxygen depletion, which creates anaerobic conditions. The presence of hydrogen sulfide makes the environment toxic for most of the biota. Detected hydrocarbons, especially PAHs easily enter the food chain and may cause cancer and mutagenic reactions of biota and humans. Organic petrology of six organic-rich sediments from New York Harbor illustrates a diverse population of anthropogenic and natural organic components. Three core samples (V-2, AC-4, and HV-3) contain coarse-textured organic matter. A slim majority of those components are anthropogenic. They are derived mainly from coal combustion by-products. The other two core samples (AC-6 and T-1) contain mainly very fine-grained organic matter. A majority of them are amorphous organic matter (AOM) that is derived from bacterial degradation of modern organic matter. Radionuclide dating (¹³⁷Cs, K-40, Pb-210) shows post-1950 components for the shallowest intervals in the cores (<30 cm). The post-1950 sediment, distributed in the tops of core, is recycled material from the dumpsites. The underlying sediment has isotopic signatures that suggest dates before active dumping.  相似文献   

On a possible proton origin for type V continuum radiation from a solar flare     

M. Friedman  S. M. Hamberger 《Solar physics》1969,8(2):398-399

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Design alternatives for a domestic carbon trading scheme in the United States     

K. John Holmes  Robert M. Friedman 《Global Environmental Change》2000,10(4)

One critical aspect of the Kyoto Protocol is its flexibility in compliance. Countries or groups of countries are free to choose their own implementation strategies. Should the United States ratify the Protocol, it will most likely use emissions trading in some form to implement this accord. Two variations on a US domestic carbon trading system are presented here. One is an auction system controlling carbon at the point of energy production and distribution. The second is a hybrid system allocating permits to large combustors and controlling smaller sources through standards. Within this paper we describe and compare the main attributes of each system. Separate sections also discuss various methods for allocating permits and incorporating standards.  相似文献