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1.
An Example of Island-Arc Petrogenesis: Geochemistry and Petrology of the Southern Luzon Arc, Philippines 总被引：7，自引：1，他引：6
DEFANT MARC J.; MAURY REN? C.; RIPLEY EDWARD M.; FEIGENSON MARK D.; JACQUES DARIO 《Journal of Petrology》1991,32(3):455-500
Volcanism throughout the Luzon arc is associated with eastwardsubduction of the South China Sea floor along the Manila Trench.The southern section of the arc, the focus of this study, extendsfrom the Lingayen-Dingalan fault to the small islands just southof Luzon. Two segments appear to exist along this section ofthe arc the northern Bataan and southern Mindoro segments whichare separated by the Macolod Corridor. The volcanic rocks have typical arc phenocryst mineralogies:olivine, clinopyroxene, plagioclase, and titanomagnetite inthe most mafic rocks and clinopyroxene, plagioclase, orthopyroxene,titanomagnetite, ? amphibole in the more felsic samples. Complexzoning, sieve textures, and decoupling of incompatible traceelements suggest that processes such as assimilation have takenplace. The rocks from the study area range from basalts to rhyolitesand show typical calc-alkaline features. The rocks of the MacolodCorridor and Mindoro segment are particularly enriched in largeion lithophile elements (LILE), light rare earth elements (LREE),and radiogenic Sr compared with the Bataan segment. The datafall within the mantle array on Sr-Nd isotopic diagrams andgrade toward higher Sr and lower Nd isotopic values from northto south. A likely source for the volcanics of this study is either amid-ocean ridge basalt (MORB)-type mantle that undergoes higherdegrees of partial melting than regions involved in MORB generationor a previously depleted source. We suggest that the high fieldstrength element (HFSE) anomalies have been derived throughdifferential element partitioning during fluid transport fromthe subducted lithosphere to the mantle wedge. Continental crustal material seems to play a significant roleparticularly in the Macolod Corridor and the Mindoro segment,based on the high LILE, La/Sm ratios, radiogenic Sr isotopes,and 18O values. The Macolod Corridor and the Mindoro segmenthave undergone source contamination by crustal material fromthe North Palawan-Mindoro crustal block either during the collisionof this block with the Manila Trench or by subduction of sedimentsrich in this crustal material. A similar component has alsobeen detected in the Bataan segment but in minor amounts. Thetrace element and isotopic differences between the northernand southern sections of the arc are interpreted in terms ofvariable composition (i. e., variable amounts of a crustal componentintroduced from the Palawan-Mindoro crustal terrain) of themetasomatic fluids released into the source. 相似文献
2.
MARC J.P. GOUW 《Sedimentology》2008,55(5):1487-1516
Ancient fluvial successions often act as hydrocarbon reservoirs. Sub‐surface data on the alluvial architecture of fluvial successions are often incomplete and modelling is performed to reconstruct the stratigraphy. However, all alluvial architecture models suffer from the scarcity of field data to test and calibrate them. The purposes of this study were to quantify the alluvial architecture of the Holocene Rhine–Meuse delta (the Netherlands) and to determine spatio‐temporal trends in the architecture. Five north–south orientated cross‐sections, perpendicular to the general flow direction, were compiled for the fluvial‐dominated part of the delta. These sections were used to calculate the width/thickness ratios of fluvial sandbodies (SBW/SBT) and the proportions of channel‐belt deposits (CDP), clastic overbank deposits (ODP) and organic material (OP) in the succession. Furthermore, the connectedness ratio (CR) between channel belts was calculated for each cross‐section. Distinct spatial and temporal trends in the alluvial architecture were found. SBW/SBT ratios decrease by a factor of ca 4 in a downstream direction. CDP decreases from ca 0·7 (upstream) to ca 0·3 (downstream). OP increases from less than 0·05 in the upstream part of the delta to more than 0·25 in the downstream delta. ODP is approximately constant (0·4). CR is ca 0·25 upstream, which is approximately two times larger than in the downstream part of the delta. Furthermore, CDP in the downstream Rhine–Meuse delta increases after 3000 cal yr BP. These trends are attributed to variations in available accommodation space, floodplain geometry and channel‐belt size. For instance, channel belts tend to narrow in a downstream direction, which reduces SBW/SBT, CDP and CR. Tectonics cause local deviations in the general architectural trends. In addition, the positive correlation between avulsion frequency and the ratio of local to regional aggradation rate probably influenced alluvial architecture in the Rhine–Meuse delta. The Rhine–Meuse data set can be a great resource when developing more sophisticated models for alluvial architecture simulation, which eventually could lead to better characterizations of hydrocarbon reservoirs. To aid such usage of the Rhine–Meuse data set, constraints for relevant parameters are provided at the end of the paper. 相似文献
3.
Potential seasonal calibration for palaeoenvironmental reconstruction using skeletal microstructures and strontium measurements from the cold‐water coral Lophelia pertusa 
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ULRICH HEIMHOFER DANIEL ARIZTEGUI MARC LENNIGER STEPHEN P. HESSELBO DAVID M. MARTILL ARISTOTELES M. RIOS‐NETTO 《Sedimentology》2010,57(2):677-694
The laminated limestones of the Early Cretaceous Crato Formation of the Araripe Basin (North‐eastern Brazil) are world‐famous for their exceptionally well‐preserved and taxonomically diverse fossil fauna and flora. Whereas the fossil biota has received considerable attention, only a few studies have focused on the sedimentary characteristics and palaeoenvironmental conditions which prevailed during formation of the Crato Fossil Lagerstätte. The Nova Olinda Member represents the lowermost and thickest unit (up to 10 m) of the Crato Formation and is characterized by a pronounced rhythmically bedded, pale to dark lamination. To obtain information on palaeoenvironmental conditions, sample slabs derived from three local stratigraphic sections within the Araripe Basin were studied using high‐resolution multiproxy techniques including detailed logging, petrography, μ‐XRF scanning and stable isotope geochemistry. Integration of lithological and petrographic evidence indicates that the bulk of the Nova Olinda limestone formed via authigenic precipitation of calcite from within the upper water column, most probably induced and/or mediated by phytoplankton and picoplankton activity. A significant contribution from a benthonic, carbonate‐secreting microbial mat community is not supported by these results. Deposition took place under anoxic and, at least during certain episodes, hypersaline bottom water conditions, as evidenced by the virtually undisturbed lamination pattern, the absence of a benthonic fauna and by the occurrence of halite pseudomorphs. Input of allochthonous, catchment‐derived siliciclastics to the basin during times of laminite formation was strongly reduced. The δ18O values of authigenic carbonate precipitates (between ?7·1 and ?5·1‰) point to a 18O‐poor meteoric water source and support a continental freshwater setting for the Nova Olinda Member. The δ13C values, which are comparatively rich in 13C (between ?0·1 and +1·9‰), are interpreted to reflect reduced throughflow of water in a restricted basin, promoting equilibration with atmospheric CO2, probably in concert with stagnant conditions and low input of soil‐derived carbon. Integration of lithological and isotopic evidence indicates a shift from closed to semi‐closed conditions towards a more open lake system during the onset of laminite deposition in the Crato Formation. 相似文献
5.
DAVIDE BASSI YASUFUMI IRYU MARC HUMBLET HIROKI MATSUDA HIDEAKI MACHIYAMA KEIICHI SASAKI SHINYA MATSUDA KOHSAKU ARAI TAKAHIKO INOUE 《Sedimentology》2012,59(7):2024-2041
Sandy and gravelly carbonate sediments found off Kikai‐jima, southern Japan, a coral reef‐related island shelf, represent the northernmost sub‐tropical, carbonate deposits in the Central Ryukyu Islands (Ryukyus). On the Kikai‐jima shelf, at water depths of 61 to 105 m, these sediments are characterized by macroid pavements. Since the abundance of very small and of exceptionally large macroids may indicate specific hydrodynamic controls regarding constraints on growth and taphonomy, the detailed analysis of recent and fossil macroid pavements is meaningful ecologically and environmentally. Macroids, ranging in size from ca 25 to 130 mm in diameter, are spheroidal and sub‐spheroidal in shape and consist mainly of the encrusting foraminifer Acervulina inhaerens and subordinate thin encrusting and lumpy coralline algae. Accessory components include bryozoans, serpulids and, to a lesser extent, encrusting arborescent foraminifera (Homotrema and Miniacina). Low sedimentation rates and occasional movement due to current action are indicated by sizes, shapes and growth‐forms of the studied macroids, the Entobia–Gastrochaenolites–Trypanites–Maeandropolydora ichnocoenosis and the ‘Bioerosion Index’ for coated grains (introduced herein). The deep‐water tidally induced current energy was sufficient to maintain multi‐directional growth (spheroidal shapes) of the larger macroids and to initiate macroid growth using the diverse biogenic remnants as nuclei. The asymmetrical inner arrangement suggests possible periods of stability for the macroids. The residence time of the coated grain in its original environment determines the size and morphology of the macroid and the selection of coating organisms. The composition of the coating community is mainly a consequence of component growth rates in relation to turnover time and residence time. Long‐term studies are needed to assess the spatial and temporal resolution of present‐day encrusting communities across biogeographic provinces and shelf to slope regions. 相似文献
6.
JASON M. DORTCH LEWIS A. OWEN MARC W. CAFFEE PHIL BREASE 《Boreas: An International Journal of Quaternary Research》2010,39(2):233-246
Dortch, J. M., Owen, L. A., Caffee, M. W. & Brease, P. 2009: Late Quaternary glaciation and equilibrium line altitude variations of the McKinley River region, central Alaska Range. Boreas, 10.1111/j.1502‐3885.2009.00121.x. ISSN 0300‐9483 Glacial deposits and landforms produced by the Muldrow and Peters glaciers in the McKinley River region of Alaska were examined using geomorphic and 10Be terrestrial cosmogenic nuclide (TCN) surface exposure dating (SED) methods to assess the timing and nature of late Quaternary glaciation and moraine stabilization. In addition to the oldest glacial deposits (McLeod Creek Drift), a group of four late Pleistocene moraines (MP‐I, II, III and IV) and three late Holocene till deposits (‘X’, ‘Y’ and ‘Z’ drifts) are present in the region, representing at least eight glacial advances. The 10Be TCN ages for the MP‐I moraine ranged from 2.5 kyr to 146 kyr, which highlights the problems of defining the ages of late Quaternary moraines using SED methods in central Alaska. The Muldrow ‘X’ drift has a 10Be TCN age of ～0.54 kyr, which is ～1.3 kyr younger than the independent minimum lichen age of ～1.8 kyr. This age difference probably represents the minimum time between formation and early stabilization of the moraine. Contemporary and former equilibrium line altitudes (ELAs) were determined. The ELA depressions for the Muldrow glacial system were 560, 400, 350 and 190 m and for the Peters glacial system 560, 360, 150 and 10 m, based on MP‐I through MP‐IV moraines, respectively. The difference between ELA depressions for the Muldrow and Peters glaciers likely reflects differences in supraglacial debris‐cover, glacier hypsometry and topographic controls on glacier mass balance. 相似文献
7.
D. MARC AUDET 《Sedimentology》1995,42(2):355-373
A continuum mechanics model for the gravitational compaction of sediments is derived by assuming that the sediments are normally pressured and in a one-dimensional state of stress. Sediment strength is characterized in terms of effective stress laws adopted from soil mechanics. The model is a relatively simple mathematical formula that gives the porosity as a function of burial depth. The shape of the porosity profile is controlled by two mechanical parameters, the compression index and the void ratio at an effective stress of 100 kPa. The model was verified by analysing the porosity—depth data of oozes and chalk from the Ontong Java Plateau, gathered during Leg 130 of the Ocean Drilling Program. The mechanical parameters of the sediments were estimated using a least-squares method to fit the theoretical profile to the porosity data. The theoretical profile described accurately the ooze porosity data over depth ranges of 100 m or more. However, over smaller length-scales of 10–50 m there were systematic deviations between the theoretical porosity values and the ooze porosity data. The porosity deviations correlated with variations in the mean grain size of the sediments, due in part to changes in the foraminifera abundance. In the case of the oozes, the estimated mechanical parameters were consistent with published values obtained from one-dimensional compression tests. In contrast, the estimated mechanical properties for the chalks differed from published values. The chalk porosities were lower than could be explained by mechanical compaction. This explanation is supported by the compressional (P-wave) velocity data. In the chalk sections, the P-wave velocity increases more rapidly with burial depth than it does in the ooze sections, suggesting that sediment elastic properties are increasing due to interparticle binding. 相似文献
8.
High Field Strength Element Enrichment of Pliocene--Pleistocene Island Arc Basalts, Zamboanga Peninsula, Western Mindanao (Philippines) 总被引：37，自引：0，他引：37
SAJONA FERNANDO G.; MAURY REN C.; BELLON HERV; COTTEN JOSEPH; DEFANT MARC 《Journal of Petrology》1996,37(3):693-726
The Pliocene—Pleistocene magmatic activity of the Zamboangaare is linked to the southward subduction of the Oligocene—Mio-ceneSulu Sea back-are basin along the Sulu Trench. The magmaticproducts include small amounts of adakites dated from 3.8 to0.7 Ma, abundant Nb-enriched basalts and basaltic andesites(NEB) dated from 2 to 1 Ma and a lone calc-alkaline potassicbasaltic andesite dated at 0.4 Ma. Three kinds of NEB are distinguished:nearly primitive Mg-rich (MG) basalts displaying positive orno Nb anomalies with respect to adjacent incompatible elementsand more evolved low-K (LK) and calc-alkaline (CA) lavas which,despite their Nb enrichment, display negative Nb anomalies.Although the role of OIB-type mantle components has been advocatedto explain the HFSE enrichment of NEB, the spatial and temporalassociation of these rocks with adakites suggests a petrogeneticlink between them. Trace element characteristics of the NEBimply that amphibole and ilmenite might be present in theirsource. We suggest that these minerals could be added metasomaticallyto the mantle through hybridization by percolating slab melts,during which Nb and Ti are preferentially extracted from theadakitic melts. In an early stage (4–3 Ma) of the subductionof the young and hot Sulu Sea basin crust beneath the Zamboangapeninsula, adakitic liquids formed at depths of 75–85km. A few of them were emplaced at the surface but most wereconsumed through slab melt-mantle metasomatic reactions. Adakiteproduction and emplacement continued later (<2 Ma), whilethe Nb-enriched mantle was brought by convection to depths thatallowed its melting and the subsequent emplacement of NEB behindthe adakitic front of the Zamboanga are. KEY WORDS: adakite; metasomatism; Mindanao; Nb-enriched basalts; subduction
*Corresponding author. Present address: Mines and Geosciences Bureau, North Avenue, Diliman, 1100 Quezon City, Philippines 相似文献
9.
Zoned Poikiloblastic Garnets: P-T Paths and Syn-Metamorphic Uplift through 30 km of Structural Depth, Wopmay Orogen, Canada 总被引：2，自引：0，他引：2
In the early Proterozoic Wopmay Orogen (Northwest Territories,Canada), the occurrence of garnet-biotite-sillimanite/kyanite-plagioclase-quartzassemblages in pelitic schists at a variety of obliquely exposedstructural levels enables the use of calibrated geothermometersand geobarometers through 30 km of composite structural relief.Direct derivation of multipoint P-T paths from single garnetsis attained from core-to-rim microprobe analyses of zoned poikiloblasticgarnets, which contain biotite, plagioclase, quartz, and lesscommonly Al2SiO5 inclusions. The documented garnet zoning andthe entrapment of the mineral inclusions is compatible withpartial-equilibrium growth models. The lack of significant diffusionre-equilibration in the garnet interiors is favored by samplerestriction to medium-grade schists and is attested by the preservationof normal-zoning profiles, the lack of garnet diffusion babesaround biotite inclusions, the matching composition trends ofgarnet-core to -rim plagioclase inclusions with those of zonedmatrix plagioclase grains, and the systematic variation of thederived P-T data. Only the garnet rims, which are characterizedby a reversal of compositional trends and by textural resorption,are interpreted to indicate local post-thermal-peak re-equilibration. The calculated P-T paths quantify segments of uplift trajectoriescorresponding to pressure drops of 2?5–1?5 kb from maximaof 9?3–5?0 kb depending on structural level. This is concurrentwith initial increases of 25–75?C to peak-temperatureconditions and is followed by variable drops in temperatureduring continued decompression. Individual paths are consistentwith modelled variations of metamorphic conditions as a functionof loading, uplift, and erosion in overthrust terrains. Consideredwith U-Pb zircon geochronological data the P-T paths, studiedas a set, indicate an average uplift rate that varies spatiallyfrom 1?5–2?7 mm y–1. This variation can be relatedto late cross folding of the orogenic internal zone, suggestingthat the syn-metamorphic uplift was structurally controlled.The distribution of peak-temperature conditions attained duringdecompression is independent of structural depth. This, andthe inverted metamorphism documented in the Wopmay Orogen, requirethat final variations in temperature result from thermal relaxationof isotherms in, and away from, a hot crustal allochthon composedin part of high-T rift-fill units and a syntectonic graniticbatholith. 相似文献
10.