New interpretation of the Franciscan mélange at San Simeon coast,California: tectonic intrusion into an accretionary prism     

Yujiro Ogawa  Ryota Mori  Toshiaki Tsunogae  Yildirim Dilek  Ron Harris 《International Geology Review》2015,57(5-8):824-842

Many concepts and interpretations on the formation of the Franciscan mélange have been proposed on the basis of exposures at San Simeon, California. In this paper, we show the distribution of chaotic rocks, their internal structures and textures, and the interrelationship between the chaotic rocks and the surrounding sandstones (turbidites). Mélange components, particularly blueschists, oceanic rocks, including greenstone, pillow lava, bedded chert, limestone, sandstone, and conglomerate, have all been brecciated by retrograde deformation. The Cambria Slab, long interpreted as a trench slope basin, is also strongly deformed by fluidization, brecciation, isoclinal folding, and thrusting, leading us to a new interpretation that turbiditic rocks (including the Cambria Slab) represent trench deposits rather than slope basin sediments. These rocks form an accretionary prism above mélanges that were diapirically emplaced into these rocks first along sinistral-thrust faults, and then along dextral-normal faults. Riedel shear systems are observed in several orders of scale in both stages. Although the exhumation of the blueschist blocks is still controversial, the common extensional fractures and brecciation in most of the blocks in the mélanges and further mixture of various lithologies into one block with mélange muddy matrix indicate that once deeply buried blocks were exhumed from considerable depths to the accretionary prism body, before being diapirically intruded with their host mélange along thrust and normal faults, during which retrograde deformation occurred together with retrograde metamorphism. Recent similar examples of high-pressure rock exhumation have been documented along the Sofugan Tectonic Line in the Izu forearc areas, in the Mineoka belt in the Boso Peninsula, and as part of accretionary prism development in the Nankai and Sagami troughs of Japan. These modern analogues provide actively forming examples of the lithological and deformational features that characterize the Franciscan mélange processes.  相似文献   

Adsorption of Fluoride on the Raw and Modified Cement Clay          下载免费PDF全文

Ayse Dilek Atasoy  Muge Ozdemir Sahin 《洁净——土壤、空气、水》2014,42(4):415-420

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Geochemical Characterization of Intermediate to Silicic Rocks in the Global Ophiolite Record     

Yildirim DILEK  Harald FURNES 《《地质学报》英文版》2017,91(Z1):8-9

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Spatiotemporal meteorological drought assessment: a case study in south-east Australia     

Yildirim  Gokhan  Rahman  Ataur 《Natural Hazards》2022,111(1):305-332

Natural Hazards - An understanding on different aspects of droughts is crucial for effective water resources management. Australia has experienced notable droughts in recent years. The present...  相似文献   

Homogeneity and trend analysis of rainfall and droughts over Southeast Australia     

Yildirim  Gokhan  Rahman  Ataur 《Natural Hazards》2022,112(2):1657-1683

Natural Hazards - This study investigates rainfall and drought characteristics in southeastern Australia (New South Wales and Victoria) using data from 45 rainfall stations. Four homogeneity tests...  相似文献   

Structural and Geomorphological Aspects of the Kat Landslides (Tokat—Turkey) and Susceptibility Mapping by Means of GIS     

Işik Yilmaz  Mustafa Yildirim 《Environmental Geology》2006,50(6):931-931

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Age and petrogenesis of plagiogranite intrusions in the Ankara mélange, central Turkey     

Yildirim  Dilek  Peter  Thy 《Island Arc》2006,15(1):44-57

Abstract   The Ankara mélange within the Izmir–Ankara–Erzincan suture zone in north-central Turkey includes ophiolitic fragments that represent the remnants of an oceanic basement evolved between the Sakarya and Kirsehir continental blocks in the early Mesozoic. The serpentinized upper mantle peridotites and lower crustal rocks in these ophiolites are cross-cut by dolerite and plagiogranite dykes, which show mutually intrusive relations indicating their synchronous emplacement into the pre-existing oceanic lithosphere. Zircon dating (U–Pb) of a plagiogranite dyke has revealed a concordia age of ∼179 ± 15 Ma that is interpreted here as the crystallization age of this differentiated rock. A fourth fraction of the zircon separates from this rock has also shown an inherited component greater than 1.7 Ga, possibly derived from the Precambrian core of the Rhodope–Strandja Metamorphic Massif in the Balkan Peninsula. Models for plagiogranite formation were tested and it is concluded that a high extent (<70%) of anhydrous or water-undersaturated, early amphibole-free fractionation of a basaltic melt source may have readily produced the observed REE concentrations for the Ankara mélange plagiogranites. The trace element abundances and other geochemical features of the coeval dolerite dykes are similar to those of the plagiogranites, suggesting a common melt source. The Ta–Nb patterns shown by both the plagiogranite and dolerite dykes are typical of arc-related petrogenesis and can be explained by the addition of slab-derived components to a depleted mantle wedge. The Early Jurassic ophiolitic basement and the dyke intrusions were formed in a back-arc setting between the Paleo- and Neo-Tethyan domains in the eastern Mediterranean region. The Izmir–Ankara–Erzincan Sea developed in this back-arc environment and the related suture zone had a diachronous evolutionary history.  相似文献   

A new approach to the evaluation of water-pressure test results obtained in bedrock by the US Bureau of Reclamation Method     

F. Bulut  S. Boynukalm  F. Tarhan  R. Dilek 《Engineering Geology》1996,44(1-4):235-243

As is known, the permeability coefficient of saturated and unsaturated rock masses can be found using the Bureau of Reclamation Method, which uses single and double packer water-pressure test results obtained from drillholes. The Bureau of Reclamation Method is, however, a time-consuming processes.

In this study, a new graphical method that does not necessitate the procedures mentioned above is proposed for the determination of the coefficient of permeability. This graphical method has been prepared with the idea that the amount of water injected into the testing section increases as the permeability of the rock mass increases. If the amount of average water loss in a 2-m test section is known, the average permeability coefficient of this section can be found using the proposed graphical method.  相似文献   

Air mass modification over Lake Michigan     

Wen-Yih Sun  Ahmet Yildirim 《Boundary-Layer Meteorology》1989,48(4):345-360

The modification of a relatively cold air mass over the warm water of Lake Michigan is studied by using a two-dimensional nonlinear mesoscale model. Considerable amounts of heat and water vapor are supplied from the water surface to the lower atmosphere by turbulent eddies. A convective mixed layer develops and grows toward the downwind region with stratocumulus clouds over the lake.The model simulates the warming and moistening of the mixed layer, the development of a boundary layer, the divergence and convergence of wind near the coastlines, and the turbulent fluxes.The model warming of the mixed layer across the lake was about 2.2 °K and the moistening of the mixed layer was about 0.8 g kg^–1, which are comparable to 2.7 °K and 0.8 g kg^–1 observed by Lenschow (1973). The convective boundary layer, which includes the cloud layer, subcloud layer, and superadiabatic layer near the water surface, is well simulated. The tilt of the inversion which coincides with the cloud top is also well reproduced. When a prescribed cooling rate is applied at the cloud top, stronger turbulence and a deeper cloud layer are generated. Without the cooling, the cloud is shallow and the shape of the cloud base is determined by surface conditions. The rise of the inversion is due to upward vertical motion, and deepening of the convective layer in the downwind region.  相似文献   

Field and geochemical characteristics of the Mesoarchean ( 3075 Ma) Ivisaartoq greenstone belt, southern West Greenland: Evidence for seafloor hydrothermal alteration in supra-subduction oceanic crust     

Ali Polat  Peter W.U. Appel  Robert Frei  Yuanming Pan  Y&#x;ld&#x;r&#x;m Dilek  Juan C. Ordez-Caldern  Brian Fryer  Julie A. Hollis  Johann G. Raith 《Gondwana Research》2007,11(1-2):69

The Mesoarchean (ca. 3075 Ma) Ivisaartoq greenstone belt in southern West Greenland includes variably deformed and metamorphosed pillow basalts, ultramafic flows (picrites), serpentinized ultramafic rocks, gabbros, sulphide-rich siliceous layers, and minor siliciclastic sedimentary rocks. Primary magmatic features such as concentric cooling-cracks and drainage cavities in pillows, volcanic breccia, ocelli interpreted as liquid immiscibility textures in pillows and gabbros, magmatic layering in gabbros, and clinopyroxene cumulates in ultramafic flows are well preserved in low-strain domains. The belt underwent at least two stages of calc-silicate metasomatic alteration and polyphase deformation between 2963 and 3075 Ma. The stage I metasomatic assemblage is composed predominantly of epidote (now mostly diopside) + quartz + plagioclase ± hornblende ± scapolite, and occurs mainly in pillow cores, pillow interstitials, and along pillow basalt-gabbro contacts. The origin of this metasomatic assemblage is attributed to seafloor hydrothermal alteration. On the basis of the common presence of epidote inclusions in diopside and the local occurrence of epidote-rich aggregates, the stage I metasomatic assemblage is interpreted as relict epidosite. The stage II metasomatic assemblage occurs as concordant discontinuous layered calc-silicate bodies to discordant calc-silicate veins commonly associated with shear zones. The stage II metasomatic assemblage consists mainly of diopside + garnet + amphibole + plagioclase + quartz ± vesuvianite ± scapolite ± epidote ± titanite ± calcite ± scheelite. Given that the second stage of metasomatism is closely associated with shear zones and replaced rocks with an early metamorphic fabric, its origin is attributed to regional dynamothermal metamorphism. The least altered pillow basalts, picrites, gabbros, and diorites are characterized by LREE-enriched, near-flat HREE, and HFSE (especially Nb)-depleted trace element patterns, indicating a subduction zone geochemical signature. Ultramafic pillows and cumulates display large positive initial ε_Nd values of + 1.3 to + 5.0, consistent with a strongly depleted mantle source. Given the geological similarities between the Ivisaartoq greenstone belt and Phanerozoic forearc ophiolites, we suggest that the Ivisaartoq greenstone belt represents Mesoarchean supra-subduction zone oceanic crust.  相似文献