Ofioliti最新文献

{"title":"MANTLE ORIGIN OF THE ANTRONA SERPENTINITES (ANTRONA OPHIOLITE, PENNINE ALPS) AS INFERRED FROM MICROSTRUCTURAL, MICROCHEMICAL, AND NEUTRON DIFFRACTION QUANTITATIVE TEXTURE ANALYSIS","authors":"P. Tartarotti, M. Zucali, M. Panseri, S. Lissandrelli, S. Capelli, B. Ouladdiaf","doi":"10.4454/OFIOLITI.V36.I2.4","DOIUrl":"https://doi.org/10.4454/OFIOLITI.V36.I2.4","url":null,"abstract":"The Antrona ophiolite is located in the Italian side of Western Central Alps. In the Alpine nappe stack, it lies at low structural levels, being sandwiched between the overlying continental Monte Rosa Nappe (upper Penninic) and the underlying Camughera-Moncucco continental Unit (middle Penninic). The ophiolite sequence includes serpentinized ultramafites, metagabbros and mafic rocks covered by calcschists. The ultramafic portion of the Antrona ophiolite consists of serpentinized peridotites, with interbedded layers of various mafic/ultramafic rocks, and underlies the mafic rocks and metasediments. In spite of the Alpine tectonic and metamorphic evolution of the Antrona ophiolite and its heavy serpentinization, the ultramafic rocks preserve relict texture and mineralogy that allow discussing the nature of their protoliths. Olivine-clinopyroxene-spinel-bearing serpentinites still retain relict porphyroclastic texture, commonly attributed to mantle peridotites. This inference is supported by quantitative textural analysis of Lattice Preferred Orientation by neutron diffraction, performed for the first time in olivine crystals of Alpine ophiolites, suggesting T conditions > 800°C for the activation of slip systems. Mineral chemistry of fresh olivine, clinopyroxene and spinel also contribute to support the mantle nature of the serpentinite protolith. The Antrona ophiolite may thus be regarded as a fossilized fragment of oceanic lithosphere including mantle rocks, volcanics and deep-see sediments. Although their extention is smaller, the Antrona ophiolite seems to be comparable with a coherent ophiolitic slice, such as Zermatt Saas ophiolite more than with a serpentinite melange.","PeriodicalId":54690,"journal":{"name":"Ofioliti","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2011-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70968793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"MAGMATIC AND POST-MAGMATIC SIGNIFICANCE OF CHROMITITE AND ASSOCIATED PLATINUM-GROUP MINERALS (PGM) IN THE EASTERN KHOY OPHIOLITIC COMPLEX (NW IRAN)","authors":"A. Azimzadeh, F. Zaccarini, M. Moayyed, G. Garuti, O. Thalhammer, I. Uysal, M. Mirmohammadi","doi":"10.4454/OFIOLITI.V36.I2.2","DOIUrl":"https://doi.org/10.4454/OFIOLITI.V36.I2.2","url":null,"abstract":"The Khoy ophiolites are one of the largest Iranian ophiolitic complexes and are characterized by a very complicate geology, consisting of several ophiolites with different ages and geodynamic settings of formation. Few small lenticular and irregular bodies of podiform and schlieren type chromitites have been recognized in the Khoy ophiolites, occurring in the serpentinized mantle peridotites. They have massive and nodular textures. According to their chromite composition, the Khoy chromitites can be classified as Al-rich and fall clearly in the field of podiform chromitites. The magmatic chromite composition of the podiform chromitites of the Khoy ophiolites suggests that they crystallized from a MORB type melt in an extensional regime. The Khoy chromitites were altered during ocean floor metamorphisms and no magmatic silicates were preserved. The composition of chlorite occurring in the silicate matrix or in contact with chromite has been used as a geothermometer. The estimated temperatures possibly reflect the effects of low-grade metamorphism. The Khoy chromitites have very low total platinum group elements (PGE) concentration with a predominance of Os + Ir + Ru over Rh + Pt + Pd. Consistently with the geochemical data, they contain few platinum group minerals (PGM) of Ru, Ir and Os. Laurite is the most common PGM along with a minor Ir-Cu sulfide, possibly cuproiridsite, osmium and erlichmanite. Most of the PGM are magmatic in origin. They crystallized in a narrow range of temperature, around 1000 o C, at relatively low sulfur fugacity and in the absence of fluids. This observation is consistent with formation of the chromitites in a mid-oceanic ridge (MOR) rather than in a supra-subduction zone (SSZ).","PeriodicalId":54690,"journal":{"name":"Ofioliti","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2011-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70968703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Radiolarian evidence for early Cretaceous (late Barremian - early Aptian) submarine volcanic activity in the tethyan oceanic realm preserved in Karabagh (Lesser Caucasus)","authors":"G. Asatryan, T. Danelian, M. Sosson, L. Sahakyan, G. Galoyan","doi":"10.4454/OFIOLITI.V36.I2.1","DOIUrl":"https://doi.org/10.4454/OFIOLITI.V36.I2.1","url":null,"abstract":"Dating radiolarites in the ophiolitic sequences of Alpine mountain belts is important for the geodynamic reconstruction of Neo-Tethys in the Lesser Caucasus.However, radiolarian data from Karabagh are very rare. A moderately well-preserved radiolarian assemblage was obtained from radiolarites that overliepillow lavas cropping out west of the village of Vank in the mountainous region of Karabagh. The presence of the easily recognisable subspecies Aurisaturnaliscarinatus perforatus is of particular significance because it is the end member of a well studied lineage that went extinct in the early Aptian. Indeed, themiddle late Barremian - early early Aptian age range of this subspecies allows to suggest that submarine volcanic activity took place during this interval in theTethyan oceanic realm preserved in Karabagh. Given that this submarine volcanic event is more or less contemporaneous to the Aptian alkaline OIB-typelavas from the Vedi ophiolite, it is likely that the Karabagh lavas are also the expression of a volcanic activity associated to the emplacement of the sameoceanic volcanic plateau.","PeriodicalId":54690,"journal":{"name":"Ofioliti","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2011-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70968649","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"EARLY JURASSIC TO EARLY LATE CRETACEOUS RADIOLARIANS FROM THE SANTA ROSA ACCRETIONARY COMPLEX (NORTHWESTERN COSTA RICA)","authors":"A. N. Bandini, P. Baumgartner, K. Flores, P. Dumitrică, Sarah-Jane Jackett","doi":"10.4454/OFIOLITI.V36.I1.1","DOIUrl":"https://doi.org/10.4454/OFIOLITI.V36.I1.1","url":null,"abstract":"In the circum-Pacific ophiolitic belts; when no other biogenic constituents are found; radiolarians have the potential to provide significant biostratigraphic information. The Santa Rosa Accretionary Complex; which crops out in several half-windows (Carrizal; Sitio Santa Rosa; Bahia Nancite; Playa Naranjo) along the south shores of the Santa Elena Peninsula in northwestern Costa Rica; is one of these little-known ophiolitic melanges. It contains various oceanic assemblages of alkaline basalt; radiolarite and polymictic breccias. The radiolarian biochronology presented in this work is mainly based by correlation on the biozonations of Carter et al. (2010); Baumgartner et al. (1995b); and O’Dogherty (1994) and indicate an Early Jurassic to early Late Cretaceous (early Pliensbachian to earliest Turonian) age for the sediments associated with oceanic basalts or recovered from blocks in breccias or megabreccias. The 19 illustrated assemblages from the Carrizal tectonic window and Sitio Santa Rosa contain in total 162 species belonging to 65 genera. The nomenclature of tectonic units is the one presented by (Baumgartner and Denyer; 2006). This study brings to light the Early Jurassic age of a succession of radiolarite; which was previously thought to be of Cretaceous age; intruded by alkaline basalts sills (Unit 3). The presence of Early Jurassic large reworked blocks in a polymictic megabreccia; firstly reported by De Wever et al. (1985) is confirmed (Unit 4). Therefore; the alkaline basalt associated with the radiolarites of these two units (and maybe also Units 5 and 8) could be of Jurassic age. In the Carrizal tectonic window; Middle to early Late Jurassic radiolarian chert blocks associated with massive tholeitic basalts and Early Cretaceous brick-red ribbon cherts overlying pillow basalts are interpreted as fragments of a Middle Jurassic oceanic basement accreted to an Early Cretaceous oceanic Plate; in an intra-oceanic subduction context. Whereas; the knobby radiolarites and black shales of Playa Carrizal are indicative of a shallower middle Cretaceous paleoenvironment. Other remnants of this oceanic basin are found in Units 2; 6; and 7; which documented the rapid approach of the depocentre to a subduction trench during the late Early Cretaceous (Albian-Cenomanian); to possibly early Late Cretaceous (Turonian).","PeriodicalId":54690,"journal":{"name":"Ofioliti","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2011-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70968432","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Tectono-magmatic correlation of basaltic rocks from ophiolite mélanges at the North-Eastern tip of the Sava-Vardar suture Zone, Northern Croatia, constrained by geochemistry and petrology","authors":"Damir Slovenec, B. Lugović, H. Meyer, Gordana Garapić Šiftar","doi":"10.4454/OFIOLITI.V36.I1.4","DOIUrl":"https://doi.org/10.4454/OFIOLITI.V36.I1.4","url":null,"abstract":"Ophiolite melanges of Mts. Kalnik and Ivanscica form the northern sector of the Kalnik Unit and represent the northeasternmost exposed tip of the Sava- Vardar Suture Zone. Petrological; geochemical and isotopic characteristics of extrusive rock blocks incorporated in the melanges; particularly of pillow basalt altered to spilite; in association with radiolarian cherts; allow the rocks to be separated into five distinct groups. Each group has an age-marker based on the radiolarian assemblage in the associated cherts and/or on isotope dating which; along with previously published data on the Kalnik Unit; provide detailed analysis of the approximately 80 Ma long geodynamic evolution of the Repno Oceanic Domain - a part of the Meliata-Maliak ocean system. The rock groups are: (1) Late Anisian alkali basalts [(La/Lu)cn = 5.9-7.2; eNd(T) = +2.96; Cpx-TiO2 = 3-6wt%] related to a terminal phase of intracontinental rifting; (2) enriched E-MORB-type basalts [(La/Lu)cn = 2.4-2.8; eNd(T) = +4.74; Cpx-TiO2 = 2.1-2.9wt%] and depleted E-MORB-type basalts [(La/Lu)cn ~ 1.5; eNd(T) = +5.26; Cpx- TiO2 = 1.9-2.3wt%] which reflect successive proto-oceanic crust formed at the ridge during the early Ladinian and late Ladinian; respectively; (3) middle Carnian T-MORB-type basalts [(La/Sm)cn = 0.79-0.87; eNd(T) = +6.63; Cpx-TiO2 = 1.2-2.2wt%]; representing crust from an evolved spreading center; (4) NMORB- type basalts [(La/Sm)cn = 0.67-0.87; eNd(T) = +6.58; Cpx-TiO2 = 0.6-1.9wt%] with inherited supra-subduction signature that diminish from the Late Carnian basalts [(Nb/La)n = 0.81] to the Bajocian basalts [(Nb/La)n = 1.1]; and Middle Jurassic (Bathonian?) N-MORB-type basalts with recurrent subduction related influence [Nb/La)n = 0.72; (La/Sm)cn = 0.76; eNd(T) = +6.23]; (5) late Bathonian medium-Ti [(Nb/La)n = 0.24-0.72; eNd(T) = +6.30; Cpx-TiO2 = 0.6- 1.1wt%] to late Oxfordian low-Ti IAT-type basalts [(Nb/La)n = 0.12-0.22; eNd(T) = +6.31; Cpx-TiO2 = 0.2-0.6wt%] which reflect melts derived from a metasomatized and successively depleted mantle wedge in an extensional proto-arc setting.","PeriodicalId":54690,"journal":{"name":"Ofioliti","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2011-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70968498","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"GEOCHEMICAL AND PETROLOGICAL CHARACTERISTICS OF LATE TRIASSIC BASIC VOLCANIC ROCKS FROM THE KOCALI COMPLEX; SE TURKEY: IMPLICATIONS FOR THE TRIASSIC EVOLUTION OF SOUTHERN TETHYS","authors":"E. Varol, Yavuz Bedi, U. K. Tekin, Seda Uzuncimen","doi":"10.4454/OFIOLITI.V36.I1.5","DOIUrl":"https://doi.org/10.4454/OFIOLITI.V36.I1.5","url":null,"abstract":"The Kocali Complex in SE Anatolia is mainly composed of tectonically imbricated slices of pelagic rock suits (pelagic limestones; cherts; etc); platform carbonates; clastics; serpentinites and basic volcanics. It can be subdivided into four main parts as the Tarasa Unit; the Konak Unit; the Cilo Limestones and the Kale Ophiolite. In this paper; geochemical characteristics of basic volcanic rocks associated with pelagic sediments (radiolarian cherts; pelagic limestones; etc) have been studied along four stratigraphical sections (the Tarasa; the Bulam-2; the Korun-1 and the Korun-2) in the Konak and the Tarasa Units. The age of the volcanic sequences have been assigned to Late Triassic (middle Carnian to Rhaetian) based on the radiolarian data from the associated pelagic rock units. Geochemical data indicates the presence of two different types of Late Triassic volcanic rock groups characterized by E-MORB-type (Group-1 volcanites from the Tarasa Unit formed by mixing of OIB and MORB-type melts) and OIB-type (Group-2 volcanites from the Konak Unit) mantle sources. None of the samples from the Kocali Complex has characteristics of N-MORB type mantle source and was affected by crustal contamination. Based on these data; it can be suggested that all these volcanic rocks formed in a marginal oceanic basin away from the ocean ridge. The presence of Radiolaria and Bivalvia-bearing pelagic limestones and cherts associated to the basic volcanic rocks in the Kocali Complex also emphasize that they all formed in deep marine basin. Geochemical characteristics of Late Triassic volcanics in the Kocali Complex have great similarities and well-correlative to the coeval volcanics previously studied in the Southern Tethyan Belt (e.g. the Baer-Bassit region in NW Syria; the Mamonia Complex in SW Cyprus and the Antalya Nappes in SW Turkey). Taking into the consideration of the geochemical data obtained from Late Triassic basic volcanics in the Kocali Complex and geochemical characteristics of the coeval volcanics in the adjacent units in the Southern Tethyan Belt; it can be suggested that rifting age of the Southern Tethyan Oceanic Basin in SE Anatolia is probably earlier than early Late Triassic (middle Carnian time).","PeriodicalId":54690,"journal":{"name":"Ofioliti","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2011-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70968566","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"THE GEODYNAMIC SETTING OF THE NAIN OPHIOLITES, CENTRAL IRAN: EVIDENCE FROM CHROMIAN SPINELS IN THE CHROMITITES AND ASSOCIATED ROCKS","authors":"Javad Mehdipour Ghazi, M. Moazzen, Mohammad Rahghoshay, H. S. Moghadam","doi":"10.4454/OFIOLITI.V36.I1.3","DOIUrl":"https://doi.org/10.4454/OFIOLITI.V36.I1.3","url":null,"abstract":"In central Iran; to the northwest of the Central Iranian micro-continental (CIM) block; the coloured melange is characterized by widespread ophiolite blocks. In the Nain area; these ophiolite blocks; known as Nain ophiolites; are mainly composed of mantle peridotites. Based on field and petrographic observations and on the chemistry of Cr-spinels; two types of chromitites have been recognized in the Nain ophiolites. The first type occurs as chromitite patches within the harzburgites. The Cr number [Cr# = 100*Cr/(Cr+Al)] of the Cr-spinels varies between 58 and 63 in chromitite patches and 39-40 in harzburgites. Calculated amount of Al2O3 and ratio of FeO/MgO in the parental melts of the chromitite patches indicate a boninitic melts for the source magmas of the Cr-spinels. The REE patterns for the studied harzburgites and lherzolites are similar to those from abyssal peridotites. These characteristics suggest a back-arc basin setting for the generation of the chromitite patches as well as of the harzburgites and lherzolites from the Nain ophiolites. The second type of chromitites occurs as lenses (chromitite pods) in dunites. The Cr number of Cr-spinels of these chromitites varies between 69 and 73. The Cr-spinels of these chromitites also show a boninitic nature for the parental melts. These characteristics of chromitite lenses show that they were generated at an arc setting. Therefore; intra-oceanic subduction in the Nain basin in Early Cretaceous can be proposed on the basis of these data on the origin of the chromitite lenses. Intra-oceanic rifting in a back-arc setting generated an oceanic back-arc basin in the Nain area in Late Cretaceous.; The chromitite patches and the studied harzburgites and lherzolites were likely formed in the mantle beneath the back-arc basin. On the whole; the field and petrographic observations as well as the degree of partial melting; calculated on the basis of the Cr#; suggest that the genesis of these rocks can be explained according to a mixed open-channel cumulate/rock-reaction model.","PeriodicalId":54690,"journal":{"name":"Ofioliti","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2011-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70968492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"CHRONOSTRATIGRAPHIC FRAMEWORK OF THE EXTERNAL LIGURIAN UNITS (LATE CRETACEOUS, NORTHERN APENNINES, ITALY) BASED ON CALCAREOUS NANNOFOSSILS","authors":"R. Catanzariti, N. Perilli","doi":"10.4454/OFIOLITI.V36.I1.2","DOIUrl":"https://doi.org/10.4454/OFIOLITI.V36.I1.2","url":null,"abstract":"The study of calcareous nannofossil assemblages recovered from the External Ligurian Units allows us (1) to reconstruct the distribution patterns of selected Late Cretaceous taxa; (2) to identify the biohorizons helpful in recognizing and characterizing the standard zones of Sissingh (1977); some of which have been grouped; and (3) to propose a synthesis of the ages achieved until now for the External Ligurian Units. According to the available dataset; rooted on published and unpublished data; the here proposed biostratigraphic scheme is based on 24 age-indicative taxa and 16 first occurrences; and its biostratigraphic resolution is comparable with the resolution of the scheme of Sissingh (1977); only considering FOs. Calcareous nannofossils are hence a fossil group useful to furnish a new and more complete chronostratigraphic framework of the main External Ligurian Units; helpful to better constrain the tectono-sedimentary and the geodynamic evolution of the Western Tethys Domain.","PeriodicalId":54690,"journal":{"name":"Ofioliti","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2011-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70968487","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"DEFORMATION PATTERN OF THE PALAEOZOIC UNITS OF THE TETHYAN SUTURE IN THE CENTRAL BALKAN PENINSULA: A NEW INSIGHT FROM STUDY OF THE BUKULJA-LAZAREVAC PALAEOZOIC UNIT (SERBIA)","authors":"B. Trivic, V. Cvetkovic, Biljana Smiljanić, Rodoljub Gajić","doi":"10.4454/OFIOLITI.V35I1.384","DOIUrl":"https://doi.org/10.4454/OFIOLITI.V35I1.384","url":null,"abstract":"This study presents and discusses new data about the lithology and deformation style of the Bukulja-Lazarevac Palaeozoic Unit (BLPz) and compares its characteristics to those exhibited by the adjacent Palaeozoic units of the complex suture of the central Balkan Peninsula, namely: the Drina-Ivanjica (DIU), the Jadar Block (JBU) and the Diaina Palaeozoic (DPz) Units. The BLPz consists of four metasedimentary and metaigneous formations metamorphosed under greenschist facies conditions. Only rare rocks show evidences of an earlier metamorphism of amphibolites facies conditions. The BLPz is lithologically similar to DIU and DPz whereas JBU is different. The study of deformation suggests that BLPz rocks underwent two ductile tectonic events, referred to as D1 and D2, and one brittle event, referred to as D3. The D1 structures are small-scale isoclinal and oblique folds with subrounded hinges and statistical B1 axes dipping around 5-20o towards E-ESE and SE. The D2 structures appear as m- to dm-sized folds formed on the limbs of the larger fold structures. Statistically, B2 axes are mainly dipping to SE, subordinately to NW and SW. The angle between B1 and B2 axes is uniform ranging from 35o to 45o. Evidences for two similar deformation events are recorded in DIU, JBU and DPz, as well. Reconstruction of the original position of B1 axes was made by rotating their measured directions around the statistic directions of B2 fold axes. The obtained results imply that the B1 axes in the northern part of DIU (Drina Block) and JBU have the same primary orientation striking NE-SW. The southern part of DIU (Ivanjica Block) and BLPz Units are characterized by E-W oriented B1 structures. Such organization suggests that all the studied Palaeozoic units probably underwent similar events of ductile deformation. These results argue in favor of the hypothesis that these units represented integral parts of Adria, and obtained their present relationships during post-Jurassic nappe stacking.","PeriodicalId":54690,"journal":{"name":"Ofioliti","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2010-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70968338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Base metal (BM) and platinum-group elements (PGE) mineralogy and geochemistry of the elmaslar chromite deposit (Denizli, sw turkey): implications for a local BM and PGE enrichment","authors":"Mehmet Akbulut, Ö. Pi̇şki̇n, S. Arai, I. Özgenç, Fevzi Minareci","doi":"10.4454/OFIOLITI.V35I1.383","DOIUrl":"https://doi.org/10.4454/OFIOLITI.V35I1.383","url":null,"abstract":"The Elmaslar Chromite Deposit (ECD) in Denizli (SW Turkey) consists of chromitite enveloped by highly refractory replacive dunite within a depleted harzburgite. The composition of chromian spinel is Cr-rich suggesting derivation from boninitic melt-peridotite interaction beneath a supra-subduction zone. The chondrite normalized PGE patterns show predominance of Ir-group (IPGE) over Pd-group PGE (PPGE) that is consistent with ophiolitic podiform chromitites in general. The primary PGM paragenesis of ECD mainly consists of laurite-erlichmanite series with minor Pd bearing phases. Dominance of Osrich laurite over the Os-poor ones suggests initially high fS2 during crystallization of chromitite. It also indicates a slow cooling rate of the chromitite parent melt. Coexistence of irarsite with erlichmanite suggests increase in As activity during late stages of chromitite crystallization. One peculiar contact zone sample with disseminated-massive chromitite enveloped by dunite shows unusually high PPGE content and positive-sloped chondrite normalized PGE pattern. This enrichment is attributed to a two stage process: (i) primary and local sulfur saturation, (ii) followed by secondary hydrothermal alteration causing smallscale remobilization and precipitation of PGE. No mode of occurrence is suggested for the primary and local sulfur saturation stage, because there is no direct field evidence on the geological setting of the sample. However, it is clear that the effects of this event were limited and not deposit wide. The secondary enrichment of PGE is mainly attributed to introduction of fluids during serpentinization. The amphibole-pyroxene-spinel-silica-carbonate rocks found in the stockpiles of ECD are remarkable. The role of these rocks, in the secondary PGE enrichment in ECD stays to be questioned. They mark further low-temperature CO2-metasomatism in ECD and provide promising indicators for investigating secondary PGE occurrences in chromitites.","PeriodicalId":54690,"journal":{"name":"Ofioliti","volume":null,"pages":null},"PeriodicalIF":1.3,"publicationDate":"2010-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70968242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}