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1.
The petrography and mineralogy of a coarse-grained eclogitelens from the La Rinconada Group of northeastern Margarita Island,Venezuela, reflect the metamorphic evolution of the rock. Omphacite+ garnet + paragonite + barroisite + epidote + rutile/ilmenite+ quartz + pyrite + apatite represents the stable assemblagemarking the culmination of a single metamorphic episode. Electronmicroprobe analyses of the major minerals indicate an affinitywith Smulikowski's low-temperature ‘ophiolitic’type. Schreinemakers relationships among the mineral phasesallow the observed complex reaction relations to be explainedas late-stage depressurization effects. The crystallizationof eclogite instead of amphibole gneiss, as in the chemicallyidentical country rock, must be related to a lower H2O in theaqueous fluid phase attending metamorphism. It is inferred frommineralogical stability data that the ‘culmination assemblage’was stable at approximately 450–525 °C and 11.5–13.5kb load pressure, and that depressurization to less than 5 kboccurred at slightly increasing metamorphic temperatures. 相似文献
2.
Lijing CHENG John ABRAHAM Kevin E.TRENBERTH John FASULLO Tim BOYER Michael E.MANN Jiang ZHU Fan WANG Ricardo LOCARNINI Yuanlong LI Bin ZHANG Fujiang YU Liying WAN Xingrong CHEN Licheng Feng Xiangzhou SONG Yulong LIU Franco RESEGHETTI Simona SIMONCELLI Viktor GOURETSKI Gengxin CHEN Alexey MISHONOV Jim REAGAN Guancheng LI 《大气科学进展》2023,40(6):963-974
Changes in ocean heat content(OHC), salinity, and stratification provide critical indicators for changes in Earth’s energy and water cycles. These cycles have been profoundly altered due to the emission of greenhouse gasses and other anthropogenic substances by human activities, driving pervasive changes in Earth’s climate system. In 2022, the world’s oceans, as given by OHC, were again the hottest in the historical record and exceeded the previous 2021 record maximum.According to IAP/CAS data, ... 相似文献
3.
Lijing CHENG John ABRAHAM Kevin ETRENBERTH John FASULLO Tim BOYER Ricardo LOCARNINI Bin ZHANG Fujiang YU Liying WAN Xingrong CHEN Xiangzhou SONG Yulong LIU Michael EMANN Franco RESEGHETTI Simona SIMONCELLI Viktor GOURETSKI Gengxin CHEN Alexey MISHONOV Jim REAGAN Jiang ZHU 《大气科学进展》2021,38(4):523-530
The long-term warming of the ocean is a critical indicator of both the past and present state of the climate system. It also provides insights about the changes to come, owing to the persistence of both decadal variations and secular trends,which the ocean records extremely well(Hansen et al., 2011;IPCC, 2013;Rhein et al., 2013;Trenberth et al., 2016;Abram et al., 2019). 相似文献
4.
Unusual corundum-fuchsite rocks with Al2O3 contents up to 89per cent and Cr2O3 values up to 2.8 per cent were investigatedfrom two localities in Zimbabwe and Transvaal. They form lenseswithin volcano-sedimentary series of different metamorphic gradesand are closely associated with metamorphic ultramafics. In Zimbabwe the corundum contains up to 3.8 wt. per cent Cr2O3,and fuchsite up to 3.7 per cent Cr2O3. Coexisting minerals areandalusite (2 per cent Cr2O3), chlorite (3.2 per cent Cr2O3),complex margarite solid solutions, tourmaline (4.9 per centCr2O3), dispore (1.1 per cent Cr2O3), and rutile (1.9 per centCr2O3); gersdorffite (NiAsS), wehrlite (BiTe), and native bismuthare occasional opaque accessories. The minerals from the Transvaallocality are generally poorer in Cr2O3. Important parageneticdifferences are the lack of diaspore, tourmaline and margarite,the occurrence of kyanite (0.9 per cent Cr2O3) instead of andalusite,exsolution bodies of complex CrFeAl-oxides in rutile, and theappearance of biotite and plagioclase. Both biotite and fuchsitemay be rich in Ba. Critical mineral assemblages indicate that the Zimbabwe rockswere metamorphosed at temperatures not greatly exceeding 400°C and at pressures below 3.5 kb, those from Transvaal near600 °C at or above 5 kb. The textures suggest that the extremeAl-enrichment did not occur during metamorphism but essentiallyprior to it or at least in its early stages. Major and minor element analyses of the rocks from both localitiesshow that they are strongly enriched in the elements Al, Cr,B, V, and As, and locally also in K, Rb, Ni, Sb, Bi, and Te,whereas they are depleted in Si, Mg, Fe, Mn, Na, Ca, S, Cu,Zn, Ga, Sr, and Y. During their formation a strong Al/Ga fractionationmust have taken place leading to exceptionally low Ga/Al ratios. Three modes of primary origin are discussed. (1) Formation ofa low-iron bauxite in a reducing Archaean atmosphere is consideredunlikely, ly on geochemical grounds (very high B-contents; aberrantCr/Ni ratios; low Ga and Y), partly because similar rocks arefound in a non-Archaean formation of New Zealand. (2) Metasomatismin connection with early metamorphic serpentini-zation of theultramafic country rock does not seem impossible but would haveto be utterly different from the commonly observed rodingitizationand other metasomatic zones surrounding serpentinites. (3) Amodel is proposed for premetamorphic postvolcanic exhalativealteration of ultramafic komatiitic lavas, during which theelements B, K, Rb, As, Sb, Bi, Te were deposited from the solutions,while Al, Cr, Ni, and V were concentrated as immobile remaindersof the original rock, and Mg, Si, Fe, and Ca were largely dissolvedand transported away. The mineralogy of these alteration productsmay have been governed by aluminous sulphate minerals like alunite,KAl3[SO4]2 (OH)6, which, during subsequent regional metamorphism,broke down to form, with the remaining silica, fuchsite andAl2SiO5, and without silica, diaspore and corundum, while sulphatewas carried away by the metamorphic solutions. 相似文献
5.
Abstract This study proposes an empirical approach that can lead to the sustainable management of groundwater resources. This approach enables a comprehensive understanding of an aquifer, delineates distinct hydrological scenarios, and recommends a set of operational activities for each sub-region of the aquifer. The paper focuses on the Coastal aquifer of the Gaza Strip region which has been divided into three sub-regions. The southern sub-region (WSW) is classified as scenario “+a2”, which indicates that it can be used as a multi-annual groundwater reservoir. The northern sub-region (NW-E) is designated scenario “-a2”, where the recommended operational measures include injection of freshwater in wells and cleaning of the surface environment. The third sub-region (CSE), is classified as scenario “-b2”, which requires severe management measures to correct both a negative hydrological and environmental situation. The approach also involves on-going monitoring of the aquifer, and can be considered as an empirical tool to provide preliminary guidelines for long-term groundwater management. 相似文献
6.
Lijing CHENG John ABRAHAM Kevin E. TRENBERTH John FASULLO Tim BOYER Michael E. MANN Jiang ZHU Fan WANG Ricardo LOCARNINI Yuanlong LI Bin ZHANG Zhetao TAN Fujiang YU Liying WAN Xingrong CHEN Xiangzhou SONG Yulong LIU Franco RESEGHETTI Simona SIMONCELLI Viktor GOURETSKI Gengxin CHEN Alexey MISHONOV Jim REAGAN 《大气科学进展》2022,39(3):373-385
The increased concentration of greenhouse gases in the atmosphere from human activities traps heat within the climate system and increases ocean heat content (O... 相似文献
7.
Lijing CHENG John ABRAHAM Jiang ZHU Kevin E. TRENBERTH John FASULLO Tim BOYER Ricardo LOCARNINI Bin ZHANG Fujiang YU Liying WAN Xingrong CHEN Xiangzhou SONG Yulong LIU Michael E. MANN 《大气科学进展》2020,37(2):137-142
Human-emitted greenhouse gases(GHGs)have resulted in a long-term and unequivocal warming of the planet(IPCC,2019).More than 90%of the excess heat is stored within the world's oceans,where it accumulates and causes increases in ocean temperature(Rhein et al.,2013;Abram et al.,2019). 相似文献
8.
Incorporation of uranium in modern corals 总被引：1，自引：0，他引：1
Uranium occurs in corals at three sites: 1, in organic matter; 2, adsorbed on the surfaces of skeletal aragonite; and 3, in the aragonite lattice. Organic matter incorporates from sea water by chelation 40–70 ppm uranium; skeletal aragonite incorporates only 3 ppm. However, as the organic fraction is low (0·1%), its high concentration of uranium does not significantly affect the total concentration of uranium in the coral. A negligible concentration of uranium, 40–60 ppb, is adsorbed on skeletal aragonite from which it is readily leached or exchanged. This low concentration of adsorbed uranium (<2% of the total uranium in skeletal aragonite) is related to the very small specific surface area (1·5–1·8 m2/g of the corals. 相似文献
9.
Talc occurs in direct contact with phengite in a manganiferousschist containing piemontite, spessartine, quartz, chlorite,hematite, braunite, and occasional phlogopite. The resultingtalc-phengite tie line in the AKF plot is a novelty for bothnatural rocks and the synthetic model system K2O-MgO-Al2O3-SiO2-H2Owhich contains about 95 per cent of the components making upthe four phyllosilicates present in the schist. The remainingcomponents are CuO, MnO, and minor Fe2O3, CoO, NiO in the chlorite,talc, and phlogopite, as well as Fe2O3 in the phengite. Two possibilities for the origin of the talc-phengite assemblageare discussed: 1. The presence of the components CuO etc. in the phyllosilicatesprovides additional degrees of freedom or causes shifts of reactioncurves in the synthetic model system thus creating a hypotheticalnew invariant point at intermediate pressures allowing a talc-phengitefield. 2. The rock was formed under very high water pressures whichpermit the coexistence of talc and phengite even in the puresynthetic system according to a theoretical prediction of phaserelations from limited experimental data available. 相似文献
10.
Trapezoidal-type fan deltas, lacking bottomset deposits, were studied in two different tectonic settings: extensional (rifted), and compressional (piggy-back) basins. In both cases studied fan deltas were characterized by: (i) an absence of bottomsets; (ii) development in protected or narrow basins and sub-basins confined by intrabasinal basement highs or by topographic highs, respectively; (iii) coarse-grained sediment fluxes, dominated by mass-flows forming fan deltas that prograded from steep nearshore slopes basinwards; and (iv) a high-energy environment, with powerful underflows that probably bypassed the basins and transported fine-grained sediments outside the basins. The location of channels cut by such underflows is influenced by local tectonic style. When the supplied sediments in the rifted basins overstepped the intrabasinal basement highs, trapezoidal fan deltas were replaced upwards by Gilbert-type deltas, with bottomsets. 相似文献