Cyclonic eddies and upper thermocline fine-scale structures in the Antarctic Circumpolar Current     

Leach  Harry  Strass  Volker 《Ocean Dynamics》2019,69(2):157-173

Ocean Dynamics - Mesoscale eddies in the open ocean are mostly formed by baroclinic instability, in which the available potential energy from the large-scale slope of the isopycnals is converted...  相似文献   

Origin of lunar fragmental matrix breccias—Highly siderophile element constraints     

Philipp Gleißner  Harry Becker 《Meteoritics & planetary science》2019,54(9):2006-2026

Ejecta at North Ray crater (Apollo 16) sampled a unique section of the lunar highlands not accessible at most other landing sites and provide important constraints on the composition of late accreted materials. New data on multiple aliquots of four fragmental matrix breccias and a fragment‐laden melt breccia from this site display a variety of highly siderophile element patterns which may represent the signatures of volatile element‐depleted carbonaceous chondrite‐like material, primitive achondrite, differentiated metal, and an impactor component that cannot be related to known meteoritic material. The latter component is prevalent in these rocks besides characterized by depletions in Re and Os compared to Ir, Ru and Pt, chondritic Re/Os, and a gradual depletion of Pd and Au. The observed characteristics are more consistent with fractionations by nebular processes, like incomplete condensation or evaporation, than with lunar crustal processes, like partial melting or volatilization. The impactor signature preserved in these breccias may stem from primitive meteorites with a refractory element composition moderately different from known chondrites. The presence of distinct impactor components within the North Ray crater breccias together with observed correlations of characteristic element ratios (e.g., Re/Os, Ru/Pt, Pd/Ir) in different impact lithologies of four Apollo landing sites constrains physical mixing processes ranging from the scale of gram‐sized samples to the area covered by the Apollo missions.  相似文献   

Ferroan olivine-bearing eucrite clasts found in howardites     

Andrea Patzer  Harry Y. McSween Jr. 《Meteoritics & planetary science》2018,53(6):1131-1149

We investigated several olivine-bearing, medium-grained, ophitic to subophitic eucritic clasts from three different Antarctic howardites. Based on grain size (0.5–2 mm), these clasts could represent intrusive igneous units. Based on mineral composition (pyroxene and plagioclase), they are similar to basaltic eucrites. Elemental concentrations of the major silicates and bulk mg#, however, range from those known for basaltic eucrites to those found in cumulate eucrites. Recognizable cumulus phases are absent. Conservatively speaking, the clasts examined may simply classify as relatively coarse-grained unequilibrated basaltic eucrites. Alternatively, at least one of the clasts showing intermediate grain size and a relatively primitive chemical composition (mg# 50) may sample a rock type that could be genetically placed between the basaltic and cumulate eucrite lines of origin. A minor, yet genetically meaningful common feature of the clasts studied is the occurrence of fayalitic olivine. Two distinct categories exist. They are (1) fine veinlets exclusively percolating through pyroxene and (2) more substantial (up to 100 μm wide) veins and/or interstitial deposits. Only the fine veinlets also contain variable amounts of anorthite, ilmenite, and troilite. Although both types of olivine are ferroan, textural aspects suggest distinct paths of generation. The fine veinlets are best explained by decomposition of relatively FeO-rich, heterogeneous, and locally metastable pyroxene, caused in situ by impact heating and subsequent fast cooling. The wider, often very ragged-looking monomineralic olivine fillings, on the other hand, may represent the iron-enriched portion of a highly fractionated magma.  相似文献   

Petrology and geochemistry of olivine‐phyric shergottites LAR 12095 and LAR 12240: Implications for their petrogenetic history on Mars     

Emilie T. Dunham  J. Brian Balta  Meenakshi Wadhwa  Thomas G. Sharp  Harry Y. McSween 《Meteoritics & planetary science》2019,54(4):811-835

Larkman Nunatak (LAR) 12095 and LAR 12240 are recent olivine‐phyric shergottite finds. We report the results of petrographic and chemical analyses of these two samples to understand their petrogenesis on Mars. Based on our analyses, we suggest that these samples are likely paired and are most similar to other depleted olivine‐phyric shergottites, particularly Dar al Gani (DaG) 476 and Sayh al Uhaymir (SaU) 005 (and samples paired with those). The olivine megacryst cores in LAR 12095 and LAR 12240 are not in equilibrium with the groundmass olivines. We infer that these megacrysts are phenocrysts and their major element compositions have been homogenized by diffusion (the cores of the olivine megacrysts have Mg# ~70, whereas megacryst rims and groundmass olivines typically have Mg# ~58–60). The rare earth element (REE) microdistributions in the various phases (olivine, low‐ and high‐Ca pyroxene, maskelynite, and merrillite) in both samples are similar and support the likelihood that these two shergottites are indeed paired. The calculated parent melt (i.e., in equilibrium with the low‐Ca pyroxene, which is one of the earliest formed REE‐bearing minerals) has an REE pattern parallel to that of melt in equilibrium with merrillite (i.e., one of the last‐formed minerals). This suggests that the LAR 12095/12240 paired shergottites represent the product of closed‐system fractional crystallization following magma emplacement and crystal accumulation. Utilizing the europium oxybarometer, we estimate that the magmatic oxygen fugacity early in the crystallization sequence was ~IW. Finally, petrographic evidence indicates that LAR 12095/12240 experienced extensive shock prior to being ejected from Mars.  相似文献   

Recognizing and compensating for interference from the sediment’s background organic matter and biodegradation during interpretation of biomarker data from seafloor hydrocarbon seeps: An example from the Marco Polo area seeps,Gulf of Mexico,USA     

Harry Dembicki Jr. 《Marine and Petroleum Geology》2010

A suite of seep samples from the vicinity of the Marco Polo field in the Green Canyon area of the Gulf of Mexico provides an exceptional opportunity to study the impact of interference from sediment background organic matter and alteration by biodegradation on thermogenic hydrocarbons from seafloor seeps. These seep samples contain a range in both the concentration of seeped hydrocarbons present and level of biodegradation experienced. In addition, the subsurface oil that sources the seepage was available for comparison.  相似文献   

A numerical model study of barotropic subtidal water exchange between estuary and subestuaries (tributaries) in the Chesapeake Bay during northeaster events   总被引：3，自引：0，他引：3  

Wenping Gong  Jian Shen  Kyoung-Ho Cho  Harry V. Wang 《Ocean Modelling》2009,26(3-4):170-189

Northeasters are storms that affect the Chesapeake Bay area more frequently, last for longer periods and impact larger areas than hurricanes. Their impacts on storm surge development and the water exchange between estuary and subestuaries (tributaries) in the Bay vary from one event to another. In this study, three different northeaster events were selected based on their tracks when passing through the Chesapeake Bay area. An unstructured grid finite volume model ELCIRC was utilized to examine the response of the water level of the Chesapeake Bay to three selected northeasters, and the barotropic subtidal water exchanges between the tributaries and the estuary in the Bay. Model sensitivity tests were conducted to examine various effects induced by, for example, tide–surge interaction, open boundary condition, river inflow, wetting-and-drying of the low-lying land area and the usage of 2-D or 3-D mode. The results show that excluding tide–surge interaction did not deteriorate the model performance in the lower Bay but it increased the model inaccuracy in the upper Bay and in the tributaries; using radiation boundary condition decreased the sea level variation in the Bay without appropriately specifying incoming wave; excluding wetting-and-drying of low-lying land area reduced the volume flux by approximately 5%; and using 3-D mode generally increased the water level variation in the Bay. The model predicted storm surges well for three northeaster events. Further diagnostic experiments show that the relative importance of the local and remote winds in generating storm surges in the Bay varied with different northeasters. The inverse barometeric effect played an important role in inducing storm surges for two selected northeasters. The interaction between the tributaries and the Bay proper is considerable. The impacts of the remote wind and Bay wind can be much larger than that of the tributary wind and, thus, control the hydrodynamics and mass transport in the tributaries. The Bay wind and tributary wind effects are largely affected by the wind direction and wind phase, and geographic locations of the tributaries in the Bay. The tributary wind can be dominant over the remote wind and Bay wind effects when the local wind stress and barometric pressure changes are large.  相似文献   

Petrographic and geochemical characterization of seep carbonate from Bush Hill (GC 185) gas vent and hydrate site of the Gulf of Mexico     

Dong Feng  Duofu Chen  Harry H. Roberts 《Marine and Petroleum Geology》2009

Authigenic carbonates are common at cold seep sites as a result of microbial oxidation of hydrocarbons. Seep carbonate samples were collected from the surface of the Bush Hill (Green Canyon Block 185, Gulf of Mexico), a mound containing gas hydrate. The carbonates consisted of oily, porous limestone slabs and blocks containing bioclasts and matrix. Analysis by X-ray diffraction shows that aragonite is the dominant mineral (89–99 wt% with an average of 94 wt%) in the matrix of seep carbonate. This cement occurs in microcrystalline, microspar, and sparite forms. The moderate ¹³C depletion of the seep carbonate (the most depleted one has δ¹³C value of −29.4‰, and 26 of 38 subsamples have δ¹³C values >−20.0‰) indicates that the non-methane hydrocarbons was incorporated during seep carbonate precipitation. Relative enrichment of ¹⁸O may be related to localized destabilization of gas hydrate or derived from ¹⁸O-enriched pore water originated from smectite–illite transition in the deep sediments. The total content of rare earth elements (REE) of the 5% HNO₃-treated solution of the carbonates is from 0.40 ppm to 30.9 ppm. The shale-normalized REE patterns show varied Ce anomalies from significantly negative, slightly negative, and no to positive Ce anomalies. Variable content of trace elements, total REE, and Ce anomalies in different samples and even in the different carbonate mineral forms (microcrystalline, microspar and sparite) of the same sample suggest that the formation condition of the Bush Hill seep carbonate is variable and complex, which is possibly controlled by the rate of fluid flux.  相似文献   

Understanding Stone Tools: A Cognitive Approach. David E. Young and Robson Bonnichsen. Peopling of Americas Process Series: Vol. 1. Center for the Study of Early Man,University of Maine at Orono, 312 pp, 46 fig., 28 tables, 5 appendixes. $27.00 ($37.00 outside N. America), 1984     

Harry J. Shafer 《Geoarchaeology》1986,1(2):213-215

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Spatial models with spatially lagged dependent variables and incomplete data     

Harry H. Kelejian  Ingmar R. Prucha 《Journal of Geographical Systems》2010,12(3):241-257

The purpose of this paper is to suggest estimators for the parameters of spatial models containing a spatially lagged dependent variable, as well as spatially lagged independent variables, and an incomplete data set. The specifications allow for nonstationarity, and the disturbance process of the model is specified non-parametrically. We consider various scenarios concerning the pattern of missing data points. One estimator we suggest is based on a smaller but complete subset of the sample; another is based on a larger but incomplete subset of the sample. We give large sample results for both of these cases.  相似文献   

Electronic Publishing: Economic Issues in a time of Transition     

Harry Lustig 《Astrophysics and Space Science》1997,247(1-2):117-132

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