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The Man Craton in West Africa hosts two clusters of highly micaceous kimberlites at Koidu and Tonguma with mineralogical and geochemical features transitional towards those of cratonic lamproites. To develop a better understanding of the genesis of these peculiar rocks, which have also been documented elsewhere (e.g., South Africa, China, Russia, India), we have undertaken a geochemical and isotopic study of representative fresh samples from Koidu and Tonguma. New mica Rb[sbnd]Sr dating by isotope dilution confirms the Jurassic age of Koidu (∼145 Ma) and establishes that the Tonguma dykes are marginally younger (∼138 Ma). Bulk-rock analyses of samples from both localities show strong enrichment in K2O (up to 4.4 wt%), but also CaO and CO2 (up to 24 wt% and 18 wt%, respectively), which is entirely consistent with the micaceous nature of these rocks and their variable abundance of calcite. Despite their highly potassic compositions, the incompatible trace element systematics (e.g., Ba/Nb) of these rocks are typical of archetypal kimberlites and unlike those of cratonic lamproites. The Sr-Nd-Hf isotopic composition of the bulk samples range between moderately depleted values (age-corrected 87Sr/86Sr ∼ 0.7032; εNd = +3.8; εHf = +3.9) resembling the common depleted (Prevalent Mantle or PREMA-like) kimberlite component and more geochemically enriched compositions (87Sr/86Sr ∼ 0.7058; εNd = −0.4; εHf = +0.3). The direct relationship between bulk-rock Nd isotopes and average Mg# of magmatic olivine, combined with the previously reported correlation between average Mg# of magmatic and xenocrystic olivine of lithospheric mantle derivation in these kimberlites, suggests that the observed spread in radiogenic isotope compositions stems from the following petrogenetic scenario. Primary kimberlite melts of similar asthenospheric origin with unradiogenic Sr and moderately radiogenic Nd and Hf isotopes interacted with variably metasomatised (i.e., containing phlogopite) and hence geochemically enriched lithospheric mantle wall rocks. Mass balance calculations suggest that the transfer of incompatible elements to the asthenospheric melts was mediated by incongruent melting of metasomatic components in the lithospheric mantle rather than their bulk addition. This study reinforces previous suggestions that interaction between carbonate-rich asthenospheric melts and the sub-continental lithospheric mantle can generate the range of potassic magmas observed within cratons., Chemical Geology, 630, ISSN:0009-2541, ISSN:1872-6836

The AusAEM20-WA program to acquire regional airborne electromagnetic (AEM) data at a nominal 20 km line-spacing across Western Australia is a National Collaborative Framework Agreement project between the Geological Survey of Western Australia (GSWA) and Geoscience Australia (GA), funded through the Western Australian Government's Exploration Incentive Scheme, the State government's COVID-19 recovery plan, and the Commonwealth Government's Exploring for the Future (EFTF) programs. AusAEM20-WA follows GA's and GSWA's rationale of aiming for State-wide coverage of geophysical data that provide context and confidence to encourage more detailed, higher resolution acquisition programs directed at local resource exploration. After completion of acquisition and processing by February 2023, more than 160 000 line km of data (Fig. 1) can be downloaded from GSWA's MAGIX and GA's eCat databases The data and derived products can be used to map the thickness and conductivity character of sedimentary and regolith cover to depths to 600 m, as well as the topmost portion of the underlying basement. Data, and derived products provide information on near-surface structure and can help assess mineral, energy and groundwater resource studies. Overall, the regolith-rock interface is well imaged across the State. On some sections, numerous conductive horizons within the regolith profile can be identified along with discrete paleochannels. The Phanerozoic rocks in the Canning, Perth, and Carnarvon Basins, are generally more conductive than the surrounding Precambrian rocks. The greater conductivity may be related to the higher proportion of conductive shale units, as well as higher moisture levels in the more porous and permeable sedimentary units. Preliminary camp-scale investigations across the State show that the data are useful to mineral explorers, as some conductive anomalies in the basement can be correlated to known deposits. Particularly conductive rock types such as lamproite pipes (or, at least their altered tops) can be distinguished from the surrounding sedimentary rocks. ASX announcements that followed within a few weeks of the data release have shown that explorers are using the data and prioritizing anomalies for further investigation., Open-Access Online Publication: May 31, 2023

The article describes the history of studying the diamond content of tectonic structures of the territory of Belarus. Based on the results of magnetometric, mineralogical, tectonic studies carried out by industrial geologists and scientists over the past 50 years, new scientifically substantiated criteria for the search for explosion pipes have been developed using Clifford’s rule, according to which kimberlite explosion pipes are developed within the Archean cratons, where the thickness of the lithosphere is 175–270 km, and are absent in the zones of Early Proterozoic stabilisation and tectonomagmatic activation. Explosion tubes on the African-Arabian, East Siberian, Sino-Korean and East European platforms demonstrate their confinement to the Archean cratons and may be associated with zones of paleosubduction of the Proterozoic oceanic crust beneath the Archean cratons. Based on this, the authors scientifically substantiated the hypothesis that during the closure of the Early Proterozoic paleoocean separating the Fenno-Scandinavian craton from the Volga-Ural and Sarmatian cratons, subduction of the younger crust took place under these cratons, the southwestern corner of which on the territory of Belarus is the Vitebsk granulite massif. The article concludes that the Vitebsk granulite massif is the most promising in terms of diamond-bearing on the territory of Belarus, and within its limits – the Smolensk regional deep fault at the intersection of this fault of northeastern striking with the Odessa-Gomel regional deep fault of submeridional striking south of the city of Orsha. Recommendations are given for further study of promising areas in order to determine their diamond content.

Petrological and geochemical studies of lamproites can provide useful insights into the nature of their lithospheric mantle sources, but their geochemical and mineralogical diversity has complicated our understanding of their primary/parental melt composition, volatile (CO2, H2O) inventory and magmatic evolution. To help address this issue, we present a detailed study of different generations (primary, pseudo-secondary, secondary) of crystal, and melt and fluid inclusions in olivine, Cr-spinel and perovskite from three olivine lamproites in the Ellendale Field of the West Kimberley Province (Australia) in order to understand the composition and evolution of their parental magmas. Melt inclusions in the different host minerals and from each of these localities are broadly similar to each other and consist of glass, alkali/alkali-earth (Mg-Ca-K-Na-Ba) carbonates, phosphates and chlorides, in addition to minerals typical of lamproite groundmass (fluorapatite, perovskite, phlogopite, diopside, wadeite, Mg-ilmenite, Fe-Mg-Ti-Cr spinel). The dominant volatile species in the melt and fluid inclusions is CO2 based on Raman data. Heating experiments of melt/fluid inclusions in olivine show significant phase transformations in which the carbonate may separate into an immiscible carbonate-rich sulphatebearing fraction or exsolve a CO2 fluid. Our results indicate that carbonates, along with alkali/alkali-earths, halogens and sulphur, became progressively concentrated in the West Kimberley lamproitic magmas during crystallisation, leading to the entrapment of a complex array of daughter minerals, some not previously reported from lamproites and, in some inclusions, immiscible carbonate melt. The widespread occurrence of daughter carbonates in melt/fluid inclusions in lamproite minerals is at odds with their apparent paucity in the lamproite groundmass. The presence of carbonate and the abundance of CO2-rich and H2O-poor melt and fluid inclusions are attributed to the preferential partitioning of CO2 into the vapour and retention of H2O in the magma during degassing, coupled with H2O loss by post-entrapment modification of the inclusions through H+ diffusion. (C) 2022 Published by Elsevier B.V. on behalf of International Association for Gondwana Research.

Lamproite is a rare ultrapotassic alkaline rock of petrological importance as it is considered to be derived from metasomatized lithospheric mantle, and of economic significance, being the host of major diamond deposits. A review of the nomenclature of lamproite results in the recommendation that members of the lamproite petrological clan be named using mineralogical-genetic classifications to distinguish them from other genetically unrelated potassic alkaline rocks, kimberlite, and diverse lamprophyres. The names “Group 2 kimberlite” and “orangeite” must be abandoned as these rock types are varieties of bona fide lamproite restricted to the Kaapvaal Craton. Lamproites exhibit extreme diversity in their mineralogy which ranges from olivine phlogopite lamproite, through phlogopite leucite lamproite and potassic titanian richterite-diopside lamproite, to leucite sanidine lamproite. Diamondiferous olivine lamproites are hybrid rocks extensively contaminated by mantle-derived xenocrystic olivine. Currently, lamproites are divided into cratonic (e.g. Leucite Hills, USA; Baifen, China) and orogenic (Mediterranean) varieties (e.g. Murcia-Almeria, Spain; Afyon, Turkey; Xungba, Tibet). Each cratonic and orogenic lamproite province differs significantly in tectonic setting and Sr–Nd–Pb–Hf isotopic compositions. Isotopic compositions indicate derivation from enriched mantle sources, having long-term low Sm/Nd and high Rb/Sr ratios, relative to bulk earth and depleted asthenospheric mantle. All lamproites are considered, on the basis of their geochemistry, to be derived from ancient mineralogically complex K–Ti–Ba–REE-rich veins, or metasomes, in the lithospheric mantle with, or without, subsequent contributions from recent asthenospheric or subducted components at the time of genesis. Lamproite primary magmas are considered to be relatively silica-rich (~50–60 wt.% SiO2), MgO-poor (3–12 wt.%), and ultrapotassic (~8–12 wt.% K2O) as exemplified by hyalo-phlogopite lamproites from the Leucite Hills (Wyoming) or Smoky Butte (Montana). Brief descriptions are given of the most important phreatomagmatic diamondiferous lamproite vents. The tectonic processes which lead to partial melting of metasomes, and/or initiation of magmatism, are described for examples of cratonic and orogenic lamproites. As each lamproite province differs with respect to its mineralogy, geochemical evolution, and tectonic setting there is no simple or common petrogenetic model for their genesis. Each province must be considered as the unique expression of the times and vagaries of ancient mantle metasomatism, coupled with diverse and complex partial melting processes, together with mixing of younger asthenospheric and lithospheric material, and, in the case of many orogenic lamproites, with Paleogene to Recent subducted material., La lamproïte est une roche alcaline ultrapotassique rare d'importance pétrologique car elle est considérée comme dérivée du manteau lithosphérique métasomatisé, et d'importance économique, étant l'hôte de gisements de diamants majeurs. Un examen de la nomenclature des lamproïtes conduit à la recommandation que les membres du clan pétrologique des lamproïtes soient nommés en utilisant des classifications minéralogiques génétiques pour les distinguer des autres roches alcalines potassiques génétiquement non liées, de la kimberlite et de divers lamprophyres. Les noms « kimberlite du groupe 2 » et « orangéite » doivent être abandonnés car ces types de roches sont des variétés de véritables lamproïtes restreintes au craton de Kaapvaal. Les lamproïtes présentent une extrême diversité dans leur minéralogie qui va de la lamproïte à phlogopite et olivine, à la lamproïte à leucite et phlogopite et de la lamproïte à richtérite-diopside potassique titanifère, à la lamproïte à sanidine et leucite. Les lamproïtes à olivine diamantifères sont des roches hybrides largement contaminées par l'olivine xénocristique dérivée du manteau. Actuellement, les lamproïtes sont divisées en variétés cratoniques (par exemple Leucite Hills, États-Unis; Baifen, Chine) et orogéniques (méditerranéennes) (par exemple Murcie-Almeria, Espagne; Afyon, Turquie; Xungba, Tibet). Chaque province de lamproïte cratonique et orogénique diffère significativement par le contexte tectonique et les compositions isotopiques en Sr, Nd, Pb et Hf. Les compositions isotopiques indiquent que leur source est un manteau enrichi, ayant à long terme des rapports Sm/Nd bas et Rb/Sr élevés, par rapport à la Terre globale et au manteau asthénosphérique appauvri. Toutes les lamproïtes sont considérées, sur la base de leur géochimie, comme étant dérivées d'anciennes veines minéralogiquement complexes riches en K, Ti, Ba et ETR, ou métasomes, dans le manteau lithosphérique avec ou sans contributions ultérieures de composants asthénosphériques ou subductés récents au moment de la genèse. Les magmas primaires de lamproïte sont considérés comme relativement riches en silice (~ 50–60% en poids de SiO2), pauvres en MgO (3–12% en poids) et ultrapotassiques (~ 8–12% en poids de K2O) comme le montrent les lamproïtes hyalo à phlogopite de Leucite Hills (Wyoming) ou de Smoky Butte (Montana). De brèves descriptions sont données des cheminées de lamproïtes diamantifères phréatomagmatiques les plus importantes. Les processus tectoniques qui conduisent à la fusion partielle des métasomes et / ou à l'initiation du magmatisme sont décrits comme des exemples de lamproïtes cratoniques et orogéniques. Comme chaque province de lamproïte diffère en ce qui concerne sa minéralogie, son évolution géochimique et son cadre tectonique, il n'y a pas de modèle pétrogénétique simple ou commun pour leur genèse. Chaque province doit être considérée comme l'expression unique de l'époque et des caprices du métasomatisme du manteau ancien, associée à des processus de fusion partielle divers et complexes, ainsi qu'à un mélange de matériaux asthénosphériques et lithosphériques plus jeunes et, dans le cas de nombreuses lamproïtes orogéniques, à du matériel paléogène à récent subducté.

The mineral chemistry of diamond indicator minerals is used to trace mineralizations in primary rocks such as lamproites/kimberlites and in secondary deposits. Subcalcic garnets and magnesian ilmenites are both minerals associated with the diamond potential described in many deposits in the Alto Paranaíba Igneous Province where several kimberlitic pipes and alluvial deposits occur. Our study was conducted on the Romaria diamond deposit of (Brazil), where garnet, ilmenite and tourmaline grains were recovered from a diamon-bearing breccia were analyzed under electron microprobe. The garnet composition is compatible with G10, G9 and G5 types. Ilmenite grains are Mg- to Mn-rich. Nearly 80% of the tourmaline grains are dravite-type. This association of dravite tourmaline with diamond in rocks of lamproitic affinity may be common, as evidenced in the Argyle, Ellendale, Prairie Creek, Sask, Presidente Olegário and Ymi-1 pipes. We therefore suggest a possible lamproite origin for the studied diamond deposit.

Olivine is one of the most abundant phases in kimberlites and cratonic lamproites, where it occurs as mantle-derived xenocrysts and magmatic phenocrysts or rims overgrowing xenocrystic cores, indicating its prevalence throughout most of the crystallisation sequence of these magmas. Thus, olivine can provide valuable insights into kimberlite and lamproite petrogenesis. Here, we present a detailed study of olivine compositional zoning in two lamproites (P2 and P12) of the Mesoproterozoic Wajrakarur kimberlite-lamproite field in southern India and use these data to propose a genetic link between lamproites and kimberlites in the region. Olivine macrocrysts (i.e., anhedral grains >1 mm) from the P2 and P12 intrusions are strongly zoned. Comparisons with olivine from mantle xenoliths worldwide demonstrate that the cores of olivine macrocrysts are xenocrysts derived from disaggregated mantle wall-rocks. The internal zones and overgrowth rims of olivine macrocrysts and the cores of olivine phenocrysts from P2 and P12 contain magmatic Mg-chromite and Ti-magnetite inclusions and hence crystallized from the host lamproite melt. These magmatic olivine zones show increasing Mg# (molar Mg/(Mg + Fe2+)), CaO and MnO contents with decreasing NiO. This reverse differentiation trend appears to be a characteristic feature of olivine in lamproites from the Wajrakarur field. To evaluate potential petrogenetic links between coeval lamproites and kimberlites from Wajrakarur, the composition of olivine xenocrysts (i.e., macrocryst cores) was compared with that of early crystallized olivine in P2, P12 and previously studied kimberlites and lamproites. The average Mg# of olivine macrocryst cores is directly correlated with the average Mg# of magmatic olivine in lamproites and kimberlites from Wajrakarur. Coupled with their indistinguishable Sr-Nd-Hf isotope compositions, these data suggest derivation of the Wajrakarur lamproites and kimberlites from a common source, The more Fe-rich composition of liquidus olivine in the Wajrakarur lamproites compared to coeval kimberlites suggests a higher degree of assimilation of metasomatised Fe-richer lithospheric mantle by the lamproites and provides a plausible explanation for the different petrological features of the Wajrakarur lamproites and kimberlites Our results suggest that cratonic lamproites can have a remarkably similar petrogenetic history to kimberlites. ISSN:0024-4937

Dynamic metasomatism experiments were performed by reacting a lamproite melt with garnet peridotite by drawing melt through the peridotite into a vitreous carbon melt trap, ensuring the flow of melt through the peridotite and facilitating analysis of the melt. Pressure (2–3 GPa) and temperature (1050–1125 °C) conditions were chosen where the lamproite was molten but the peridotite was not. Phlogopite was formed and garnet and orthopyroxene reacted out, resulting in phlogopite wehrlite (2 GPa) and phlogopite harzburgite (3 GPa). Phlogopites in the peridotite have higher Mg/(Mg + Fe) and Cr2O3 and lower TiO2 than in the lamproite due to buffering by peridotite minerals, with Cr2O3 from the elimination of garnet. Compositional trends in phlogopites in the peridotite are similar to those in natural garnet peridotite xenoliths in kimberlites. Changes in melt composition resulting from the reaction show decreased TiO2 and increased Cr2O3 and Mg/(Mg + Fe). The loss of phlogopite components during migration through the peridotite results in low K2O/Na2O and K/Al in melts, indicating that chemical characteristics of lamproites are lost through reaction with peridotite so that emerging melts would be less extreme in composition. This indicates that lamproites are unlikely to be derived from a source rich in peridotite, and more likely originate in a source dominated by phlogopite-rich hydrous pyroxenites. Phlogopites from an experiment in which lamproite and peridotite were intimately mixed before the experiment did not produce the same phlogopite compositions, showing that care must be taken in the design of reaction experiments.

Bu çalışmada, Haydarlı bölgesindeki volkanik kayaçlar jeolojik, mineralojikpetrografik ve jeokimyasal (ana ve iz element, çoklu element içerikleri ve izotop analizleri) özellikleri bakımından incelenmiştir. İncelemeler sonucunda volkanizmanın kökeni ve evrimine açıklık getirilmeye çalışılmıştır. Çalışma alanında volkanosedimanter birimler, piroklastik kayaçlar ve volkanitler; trakitler, trakiandezitler, lösititler, fonolitler, lamproitler, bazaltik lav ve dayklar tespit edilmiştir. Volkanosedimanter birimler tektonik aktiviteye bağlı olarak yapısal ve renk farklılıkları sunmaktadır. Piroklastik birimler, lösit bloklu ve fonolitli piroklast kayaçlar olmak üzere ikiye ayrılmakta ve bölgede geniş alan kaplamaktadır. Trakitler, fonolitler, lösititler, lamproit, bazaltik lav ve dayklar bu volkanosedimanter birimleri keserek yerleşmiştir. Bu volkanizma ürünlerinde yaygın olarak plajioklas, piroksen, amfibol, biyotit ve opak mineraller gözlenmiştir. Haydarlı volkanitlerinin jeokimyasal olarak çoğunluğunun ultrapotasik ve yüksek K’lu alkalin özellikte olduğu belirlenmiştir. Bu sonuçlar bölgedeki volkanizmanın, kirlenme-kabuksal katkıfranksiyonel kristallenmeye uğradığına işaret etmektedir. In this study, Volcanic rocks in the Haydarlı region have been studied in terms of their geological, mineralogical-petrographic and geochemical properties (main and trace elements, multiple element contents and isotope analyzes). As a result of these investigations, the origin and evolution of volcanism was tried to be explained. In the study area, volcanosedimanter units-pyroclastic rocks and volcanites, Trachites, trachyandesites, leucites, phonolites, basalts and basaltic dykes have been identified. Volcanosedimanter units exhibit structural and color differences related to tectonic activity. Pyroclastics, leucite block and phonolite pyroclast rocks cover a large area in the region. Trachites, phonolites, leucitites, lamproites, basalt and dykes have been emplaced by cutting these volcanosedimanters. Plagioclase, pyroxene, amphibole, biotite and opaque minerals have been commonly observed in these volcanism products. It is determined that most of the volcanics of Haydarlı region are ultrapotassic and high K alkaline. These results showed that the volcanism in the region underwent pollution-crustal additive-functional crystallization.

Trends in a concentration of selected trace elements in residual soils on four known diamondiferous kimberlite pipes (3, 4, 8 and 9) occurring at Lattavaram within the Wajrakarur Kimberlite Field (WKF) is attempted for the first time. The pipes 3 and 4 are exposed whereas the 8 and 9 are concealed under calcrete and colluvium. For this purpose, elements like Cr, Co, La, Nb, Ni, Mg, Sr and Zr are used to understand their concentrations in the kimberlitic soils in comparison with background granitic soils. It is observed that the soils on kimberlite pipes show conspicuous enrichment of elements such as Cr, Co, Nb, Ni, Mg and Sr when compared to soils in the country rock granitoid. However, no much variation in the elements La and Zr patterns between the kimberlitic and background soils is noticed. The high pulse in trace elements in kimberlitic soils is attributed to the presence of primary kimberlitic minerals in the soil. This particular aspect of pedogeochemistry is envisaged to be useful as an exploration tool in search of kimberlites in cratonic parts of southern India. An enrichment of Nb content upto 45 ppm in residual soils may be considered as anomalous in the craonic parts of Indian subcontinent, which needs to be confirmed and taken forward in conjunction with high-resolution geological mapping, geophysics and eventual drilling.

The article presents the results of prospecting of diamond boring within the Kuhotsko-Bilska area, which is located on the north-western slope of the Ukrainian Shield.The data of the researches of 1995–2013 made it possible to form a new view on regional and local criteria and signs of diamond-bearing area of work, including a detailed study of the material composition of breccia, to distinguish among them explosive, to discover a new type of potentially diamond- bearing structures.According to all available geological and geophysical information, specific recommendations are given for direct searches for kimberlite or lamproite bodies within promising structures and breccia occurrence.

Petrographic, mineral chemical and whole-rock geochemical characteristics of two newly discovered lamproitic dykes (Dyke 1 and Dyke 2) from the Sidhi Gneissic Complex (SGC), Central India are presented here. Both these dykes have almost similar sequence of mineral-textural patterns indicative of: (1) an early cumulate forming event in a deeper magma chamber where megacrystic/large size phenocrysts of phlogopites have crystallized along with subordinate amount of olivine and clinopyroxene; (2) crystallization at shallow crustal levels promoted fine-grained phlogopite, K-feldspar, calcite and Fe-Ti oxides in the groundmass; (3) dyke emplacement related quench texture (plumose K-feldspar, acicular phlogopites) and finally (4) post emplacement autometasomatism by hydrothermal fluids which percolated as micro-veins and altered the mafic phases. Phlogopite phenocrysts often display resorption textures together with growth zoning indicating that during their crystallization equilibrium at the crystal-melt interface fluctuated multiple times probably due to incremental addition or chaotic dynamic self mixing of the lamproitic magma. Carbonate aggregates as late stage melt segregation are common in both these dykes, however their micro-xenolithic forms suggest that assimilation with a plutonic carbonatite body also played a key role in enhancing the carbonatitic nature of these dykes. Geochemically both dykes are ultrapotassic (K 2 O/Na 2 O: 3.0–9.4) with low CaO, Al 2 O 3 and Na 2 O content and high SiO 2 (53.3–55.6 wt.%) and K 2 O/Al 2 O 3 ratio (0.51–0.89) characterizing them as high-silica lamproites. Inspite of these similarities, many other features indicate that both these dykes have evolved independently from two distinct magmas. In dyke 1, phlogopite composition has evolved towards the minette trend (Al-enrichment) from a differentiated parental magma having low MgO, Ni and Cr content; whereas in dyke 2, phlogopite composition shows an evolutionary affinity towards the lamproite trend (Al-depletion) and crystallized from a more primitive magma having high MgO, Ni and Cr content. Whole-rock trace-elements signatures like enriched LREE, LILE, negative Nb-Ta and positive Pb anomalies; high Rb/Sr, Th/La, Ba/Nb, and low Ba/Rb, Sm/La, Nb/U ratios in both dykes indicate that their parental magmas were sourced from a subduction modified garnet facies mantle containing phlogopite. From various evidences it is proposed that the petrogenesis of studied lamproitic dykes stand out to be an example for the lamproite magma which attained a carbonatitic character and undergone diverse chemical evolution in response to parental melt composition, storage at deep crustal level and autometasomatism.

We have studied mineral and chemical composition of lamproites from Kalymbaevsky Complex the Middle Trias. These lamproites were developed in Magnitogorsk and Eastern-Urals megazones of the Southern Urals. We have established the presence of olivine, phlogopite, diopside phenocrysts. We have registered the presence of globular structures, consisting of sanidine and interstitial glass. We have also shown the presence in the base of rocks microlites of aluminous diopside-augite and alkaline pyroxenes of aegirin-augite series, which previously were taken for alkaline and sub-alkaline amphiboles. We have established high sulfur concentration in the apatite which, without magmatic sulfides in the rocks, witnesses for oxidation of lamproite magmas. For the first time precise geochemical data for microelemental and isotopic Sr, Nd composition of rocks are given. It was found that the South Urals rocks have a intermediate composition between lamproites and potassium alkaline basalts. Their source was the enriched mantle with the value εNdi = +0.7-+3.9. We have shown uncertainty of geochronological data, according to which lamproite magmatism could be initiated 197-240 or 300-310 Ma.

The late Miocene (11–9 Ma) volcanic rocks of Kef Hahouner, ~40 km NE of Constantine (NE Algeria), are commonly classified as lamproites in literature. However, these rocks are characterized by an anhydrous paragenesis with plagioclase and Mg-rich olivine phenocrysts, set in a groundmass made up of feldspars, pyroxenes and opaque minerals. Thus, we classify the Kef Hahouner rocks as ultrapotassic shoshonites and latites, having K2O N 3 wt.%, K2O/Na2O N 2.5, MgO N 3–4 wt.%, SiO2 b 55–57 wt.% and SiO2/K2O b 15. All the investigated samples showprimitive mantle-normalizedmulti-element patterns typical of orogenic (arctype) magmas, i.e. enriched in LILE (e.g. Cs, Rb and Ba) and LREE (e.g. La/Yb=37–59) with respect to the HFSE, peaks at Pb and troughs at Nb and Ta. Initial isotopic ratios are in the range of 87Sr/86Sr = 0.70874–0.70961, 143Nd/144Nd = 0.51222–0.51223, 206Pb/204Pb = 18.54–18.60, 207Pb/204Pb = 15.62–15.70 and 208Pb/204Pb = 38.88–39.16. The Kef Hahouner volcanic rocks show multi-element patterns similar to the other circum-Mediterranean lamproites and extreme Sr, Nd and Pb isotopic compositions. Nevertheless, the abundant plagioclase, the presence of Al-rich augite coupled with high Al2O3 whole rock compositions (9.6–21.4 wt.%), and the absence of phlogopite are all at inconsistentwith the definition of lamproite.Wereviewed the rocks classified as lamproites worldwide, and found that many of these rocks, as for the Kef Hahouner samples, should be actually defined as “normal” potassic to ultrapotassic volcanic rocks. Even the grouping of lamproites into “orogenic” and “anorogenic” types appears questionable.

Mesozoic (125&ndash, 135 Ma) cratonic low-Ti lamproites from the northern part of the Aldan Shield do not conform to typical classification schemes of ultrapotassic anorogenic rocks. Here we investigate their origins by analyzing olivine and olivine-hosted inclusions from the Ryabinoviy pipe, a well preserved lamproite intrusion within the Aldan Shield. Four types of olivine are identified: (1) zoned phenocrysts, (2) high-Mg, high-Ni homogeneous macrocrysts, (3) high-Ca and low-Ni olivine and (4) mantle xenocrysts. Olivine compositions are comparable to those from the Mediterranean Belt lamproites (Olivine-1 and -2), kamafugites (Olivine-3) and leucitites. Homogenized melt inclusions (MIs) within olivine-1 phenocrysts have lamproitic compositions and are similar to the host rocks, whereas kamafugite-like compositions are obtained for melt inclusions within olivine-3. Estimates of redox conditions indicate that &ldquo, lamproitic&rdquo, olivine crystallized from anomalously oxidized magma (∆NNO +3 to +4 log units.). Crystallization of &ldquo, kamafugitic&rdquo, olivine occurred under even more oxidized conditions, supported by low V/Sc ratios. We consider high-Ca olivine (3) to be a fingerprint of kamafugite-like magmatism, which also occurred during the Mesozoic and slightly preceded lamproitic magmatism. Our preliminary genetic model suggests that low-temperature, extension-triggered melting of mica- and carbonate-rich veined subcontitental lithospheric mantle (SCLM) generated the kamafugite-like melts. This process exhausted carbonate and affected the silicate assemblage of the veins. Subsequent and more extensive melting of the modified SCLM produced volumetrically larger lamproitic magmas. This newly recognized kamafugitic &ldquo, fingerprint&rdquo, further highlights similarities between the Aldan Shield potassic province and the Mediterranean Belt, and provides evidence of an overlap between &ldquo, orogenic&rdquo, and &ldquo, anorogenic&rdquo, varieties of low-Ti potassic magmatism. Moreover, our study also demonstrates that recycled subduction components are not an essential factor in the petrogenesis of low-Ti lamproites, kamafugites and leucitites.

The pedogenic carbonates, found mainly in arid and semi arid regions of the world, are commonly referred to as calcretes or caliche or kankar. These are authigenic carbonate products which occur in association with soil, forming the residual regolith. Many rock types can produce calcretes upon weathering and denudation, but calcrete derived from certain rocks like kimberlite lamproite acts as an exploration guide. Calcrete is a prominent sampling medium in diamond rich countries like Australia and South Africa whereas it has not received popularity in the Indian context. Kimberlites being ultrapotassic in nature and owing to the enrichment of olivine and serpentine often produce calcrete duricrust as a capping. Recently more than twenty lamproites have been discovered in the Telangana state by the Geological Survey of India. These occurrences unravel a new panorama that the state has a substantial potential for occurrence of more kimberlite lamproite clan rocks. An attempt has been made here to test the geochemical affinity of calcretes from various locations within Nalgonda district. The geochemical data of calcrete samples of this study has been compared with published geochemical data of lamproites of Ramadugu Field, to understand their geochemical association to kimberlite lamproite. The calcretes are low in SiO2 33.92 45.1 wt , high in K2O 1.07 2.21 wt and CaO 0.78 13.61 wt . When compared to other major elements, MgO displays low concentration. The trace elements are found to be enriched in some of the samples collected in close vicinity of known lamproite occurrences. The samples show high degree of chemical weathering, alteration and compositional variation indices. It is observed that enrichment of elements like Cr, Nb, Ba, Ti, Zr etc. indicates, similar to parent kimberlite lamproite rock, favourable targets for further ground exploration in virgin areas. In the present study, two samples, towards five kilometers northeast of Vattikodu Lamproite Field, possess higher concentrations of Nb 25ppm , Ba 400 ppm , Zr 650 ppm and Ti 3500 ppm which stand out as plausible explorable targets for further ground investigations. Further investigations on these two locations are suggested to ascertain whether or not these two targets unveil new kimberlites lamproite occurrences in the area. P. Ramesh Chandra Phani | M. Srinivas "Calcrete Geochemistry in identifying Kimberlite / Lamproite Exploration Targets -A case study from Nalgonda district, Telangana, southern India" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-2 , February 2018, URL: https://www.ijtsrd.com/papers/ijtsrd9575.pdf

Calculations shown that a relatively low-temperature kimberlite magmas consolidated with decompression exploded on significant depth and formed pipes. High-temperature lamproite magmas exploded on near-surface conditions and formed mainly tuff covers. Their erosion formed diamond placers. Kimberlite magmas and their diamonds are a result of fractionation peridotite layer of magma ocean. Lamproite magmas and their diamonds are a result of fractionation of magmatic chambers in plumes. Non-kimberlite diamons of placers have lamproite plume genesis.

This study focuses on age and evolution of the Oligocene quartz latite of the Rogozna Mts. (Central Balkan Peninsula), in order to better understand the link between magmatism and formation of Pb–Zn±Ag mineralization. New 40Ar/39Ar biotite and amphibole plateau ages suggest that the Rogozna Mts. quartz latite originated through a continuous volcanic episode from 27.3±0.1 to 29.5±0.1 Ma which was immediately followed by a hydrothermal phase. The quartz latites are hypocrystalline porphyritic with phenocrysts and microphenocrysts (~60 vol.%) of plagioclase (An37–49), biotite Mg# [100×Mg / (Mg+Fetot)] b50, calcic amphibole, quartz, sanidine clinopyroxene and phlogopite (Mg#=79 to 84). The rocks display numerous disequilibrium textures, such as: sieved plagioclase phenocrysts, dissolution effects on quartz, phlogopitized biotite and amphibole crystals, and phlogopite microphenocrysts showing effects of incomplete growth (or dissolution?) and biotitization. The Rogozna Mts. quartz latites are shoshonitic in character with Na2O/K2Ob1, high LILE/HFSE ratios, strong depletions at Nb and Ti and K, Pb and U peaks on primitive mantle-normalized diagrams. They are similar to other potassic/ultrapotassic rocks in this region, in particular to those of Veliki Majdan and Rudnik (West Serbia), which are also related to Pb–Zn deposits. The evolution of the Rogozna Mts. quartz latite is modeled using a trace element binary mixing model adopting a lamproite magma and a dacite-like calc-alkaline melt as end-members. The model implies that a fractionating magma chamber (~4.5–9.5 km) undergoes cooling in the range of >850 °C–~720 °C and injection of lamproite-like melts. The injection causes an increase of temperature and a decrease of viscosity of the resulting hybrid magma, facilitating its upwelling and triggering pyroclastic eruptions. The addition of new volatiles by lamproitic melts most probably established the conditions for a hydrothermal phase above the magma chamber that was previously degassed explosively. This implies that magma mixing processes can be of great importance for the formation of Pb–Zn deposits. Similar processes are likely to have occurred in other areas with economically significant Pb–Zn–Ag± other metal mineralization in the region of the Central Balkan Peninsula (Veliki Majdan, Rudnik, Golija, Kopaonik, Avala, etc.).

The Oligocene–Pleistocene Tethyan Realm Lamproites, from the Mediterranean to Himalayas, have a clear subduction-related signature and represent one of the most exotic and rare ultrapotassic mantle-derived magmas. They share the major element and mineralogical characteristics of the lamproite clan rocks, but clearly define a distinct subgroup with respect to within-plate lamproites on the basis of a number of key trace element ratios and radiogenic isotopes. The most striking characteristic of the Tethyan Realm Lamproites is the positive correlation between Th/La (up to > 1.5) and Sm/La (up to > 0.3), which is opposite to what observed in subduction-related magmas worldwide and cannot be reconciled with typical slab recycling processes. The geochemical conundrum of the Tethyan Realm Lamproites requires a component with high Sm/La and Th/La (hence named SALATHO), in addition to a normal K2O–rich sediment melt component (with low Th/La and Sm/La). The Pb isotope composition of the Tethyan Realm Lamproites also displays a mixing array from a normal sediment melt component to a high 208Pb/206Pb and low 206Pb/204Pb end-member that can be reconciled with the SALATHO component. This end-member requires a history of high time-integrated κ (232Th/238U) and low time-integrated μ (238U/204Pb) and ought to be older than some hundreds of million years. We propose a multi-stage process for the formation of the mantle sources of the Tethyan Realm Lamproites related to the tectonic melange domains (i.e. chaotic mixture of depleted peridotite, basalt, and sediment) accreted to the Eurasia plate during the collisional events of the northward drifting continental slivers from Gondwana. In a first stage, the melange domains experienced high P and low T metamorphism with segregation and stabilisation of lawsonite and zoisite/epidote veins, which potentially match the geochemical characteristics required by the SALATHO component. Successively, the subduction of the Neotethys and Alpine Tethys oceanic plates produced normal K2O-rich sediment melts that migrated through the mantle wedge and metasomatised the depleted lithospheric mantle blocks within the chaotic melange, forming a clinopyroxene–phlogopite vein network. Eventually, the Tertiary orogenic belt collapses triggered the onset of low-degree melting of the low-solidus fractions within the melange domains, producing lamproitic magmas.

K2O-rich melts (K2O > 2 wt. %; K2O/Na2O > 1) have been described in all of the major geodynamic settings on Earth. These melts are mainly characterized by their huge K2O content, ranging between 2 – 13 wt. % and K2O/Na 2 O ratios of 1 – 40. The chemical compositions of the different K2O-rich melt groups span a very high variability, from strongly silica undersaturated melts (kamfugites, kimberlites, madupitic lamproites) to silica-rich terms (shoshonites, phlogopite lamproites). These very high K2O contents together with strong K2O/Na2O ratios cannot be derived from partial melting of fertile or depleted peridotites. Partial melting experiments have been conducted in piston cylinder apparatus on phlogopite ± amphibole-peridotite in the spinel and garnet stability fields (1 – 3 GPa) in order to determine the ability of the lithospheric mantle to produce K2O-rich melts. The presence of small amounts of fluorine in the starting material leads to stabilize phlogopite at higher temperatures than previously determined. The first degrees of melting at 1 GPa are silica-rich and their K2O contents are buffered to 4 – 6 wt. % in the presence of residual phlogopite, depending on the source fertility (lherzolite and harzburgite, respectively). In the garnet stability field at 3 GPa, low-degree melts are silica-undersaturated but are enriched in K2O, compared to the garnet stability field: from 6 to 8 wt. % in lherzolite and harzburgite sources, respectively. These results suggest that pressure is a key parameter in the mantle to produce K2O-rich melts. Partition coefficient modelings show that increasing the phlogopite proportion in the mantle source does not modify the K2O content of derived melts, but decreases their K2O/Na2O ratios. Consequently, partial melting of phlogopite-peridotite in this range of pressure cannot accounts for the highest K2O contents observed in natural lamproites and kamafugites. A series of experiments has been realized on pure phlogopite at 1 and 3 GPa, showing that derived melts are strongly enriched in K2O (12 – 14 wt. %) and share chemical affinities with lamproites. Peridotite or pyroxenite melting in the presence of phlogopite, however, do not permit to reproduce the high chemical variability of natural K2O-rich melts requires volatile-rich conditions (H2O, CO2, F) and reduced oxygen fugacities., Des liquides riches en K2O ( K2O > 2 pds. % ; K2O/Na2O > 1) sont observés dans la majeure partie des contextes géodynamiques sur Terre. Ces liquides sont principalement caractérisés par leurs teneurs en K2O variant entre 3 et 13 pds. % et des rapports K2O/Na2O de 1 – 40. Les compositions chimiques des différents groupes de liquides riches en K2O observés sont extrêmement variables, depuis des termes très sous-saturés en silice (kamafugites, kimberlites, lamproïtes madupitiques à olivine) à des termes sur-saturés en silice (shoshonites, lamproïtes à phlogopite). Ces fortes teneurs en K2O et les rapports K2O/ Na2O élevés ne peuvent pas être obtenus par la fusion de péridotites fertiles ou réfractaires. Des expériences de fusion partielle en piston-cylindre ont été réalisées sur des péridotites à phlogopite ± amphibole dans les domaines de stabilité du spinelle et du grenat (1 et 3 GPa) afin de déterminer la capacité du manteau lithosphérique à produire des liquides riches en K2O. La présence de faibles teneurs en fluor dans le matériel de départ stabilise le phlogopite à des températures supérieures aux études antérieures. Les faibles degrés de fusion obtenus à 1 GPa sont sur-saturés en silice et leur teneur en K2O est tamponnée à 4 – 6 pds. % par la présence de phlogopite résiduel pour des péridotites fertile et réfractaire, respectivement. Les expériences réalisées à 3 GPa montrent que les premiers degrés de fusion sont sous-saturés en silice mais plus riches en K2O (6 – 8 pds. % pour la lherzolite et la harzburgite, respectivement) que dans le domaine du spinelle, démontrant l’importance de la pression sur la genèse de liquides riches en K2O. Les modélisations réalisées montrent également que l’augmentation de la proportion de phlogopite dans la source ne modifie pas la teneur en K2O des liquides formés mais diminue leurs rapports K2O/Na2O. Par conséquent, la fusion de péridotite à phlogopite dans la gamme de pression étudiée ne permet pas d’obtenir des liquides aussi riches en K2O que certains lamproïtes et kamafugites. Une série d’expériences réalisée sur du phlogopite pur à 1 et 3 GPa montrent que les liquides dérivés de telles sources sont très riches en K2O (12 – 14 pds. %) et comparables aux lamproïtes. Les différentes lithologies dans le manteau ne permettent cependant pas d’expliquer la grande gamme de composition des liquides riches en K2O et nécessitent des conditions riches en éléments volatils (H2O, CO2, F) et des fugacités d’oxygène réductrices.

The Central Mediterranean region is one of the most important areas on Earth for studying subduction-related potassic and ultrapotassic magmatism, derived from partial melting of the metasomatised lithospheric mantle wedge. In this region, leucite-free (i.e., lamproite) and leucite-bearing (i.e., kamafugite, leucitite, and plagioleucitite) ultrapotassic rocks closely occur, in a time-related progression, linked to the evolution of both the mantle source and the regional tectonic regime. Time- and space-related magmatism migration followed the roll-back of the subducting slab and the anticlockwise drift of the Italian Peninsula. Leucite-free silica-rich lamproites are restricted to the early stage of magmatism and are associated with ultrapotassic shoshonites and high-K calc-alkaline volcanic rocks. Leucite-bearing (i.e., Roman Province) rocks are erupted consistently later than lamproite-like and associated shoshonitic rocks, with post-leucititic volcanism occurring in the late stage of volcanic activity with eruption of alkali-basaltic to latitic and trachytic rocks, often after major caldera-forming events. Present-day ultrapotassic volcanism is restricted to the Neapolitan area. Central Mediterranean potassic and ultrapotassic rocks are extremely enriched in incompatible trace elements with variable fractionation of Ta, Nb, and Ti in comparison to Th and large ion lithophile elements (LILE). They are also variably enriched in radiogenic Sr and Pb and unradiogenic Nd. The main geochemical and isotopic signatures are consistent with sediment recycling within the mantle wedge via subduction. A twofold metasomatism, induced by the recycle of pelitic sediments and dehydration of lawsonite-bearing schists generates the early metasomatic events that enriched the mantle wedge from which leucite-free ultrapotassic rocks (i.e., lamproite) were generated. Recycling of carbonate-rich pelites played an important role in the shift to silica-undersaturated ultrapotassic rocks (kalsilite- and leucite-bearing) of the classic ‘Roman province’.

Major and trace element compositions with Sr–Nd isotopic ratios, as well as Ar–Ar radiometric ages of the Miocene volcanic rocks from the Neogene units around Simav region (western Anatolia), are used to discuss the genetic relationship between (1) high-voluminous Lower–Middle Miocene high-potassic, calc-alkaline (HKCA) and (2) Middle Miocene small-voluminous high-MgO shoshonitic–ultrapotassic (SHO–UK) magmatic units in the region. All the HKCA rocks, including basaltic to rhyolitic (and granitic) samples, share similar trace element characteristics (enrichments of LILE and LREE and depletions in HFSE as a common feature of orogenic magmatic rocks), with subtle differences in their 87Sr/86Sr(i) ratios (basalts and rhyolites ~0.708, dacites ~0.710). Most of the samples of the high-MgO SHO–UK group are classified as shoshonite and latite, with some lamproites, sharing similar geochemical features with the other ultrapotassic rocks of the Mediterranean. All the rock groups have similar and high abundances of incompatible trace elements, and radiogenic Sr. Geochemical modeling of the trace element and isotopic ratios of the samples reveals that both the SHO–UK and HKCA groups were derived from a common mantle source which had been highly metasomatized and enriched by continental materials during partial subduction of the crustal metamorphic slices in a continental collision setting. The geochemical variations of these rocks were mainly controlled by source characteristics (such as heterogeneity) and variable degrees of partial melting and subsequent effects of fractional crystallization, with low degrees of crustal contamination. The HKCA series were derived by higher degrees of partial melting of the lithospheric mantle source than the SHO–UK rocks. The HKCA rocks then underwent two-stage fractional crystallization (clinopyroxene-dominated followed by feldspar-dominated fractionating mineral assemblages) to form the high-K calc-alkaline basalt to rhyolite series, whereas the SHO–UK rocks experienced comparatively little fractional crystallization. A tectonic scenario involving the rapidly extending and thinning of orogenic crust is compatible with the time-dependent compositional variation of the magmatic rocks. © 2015, Springer-Verlag Berlin Heidelberg.

Major and trace element compositions with Sr-Nd isotopic ratios, as well as Ar-Ar radiometric ages of the Miocene volcanic rocks from the Neogene units around Simav region (western Anatolia), are used to discuss the genetic relationship between (1) high-voluminous Lower-Middle Miocene high-potassic, calc-alkaline (HKCA) and (2) Middle Miocene small-voluminous high-MgO shoshonitic-ultrapotassic (SHO-UK) magmatic units in the region. All the HKCA rocks, including basaltic to rhyolitic (and granitic) samples, share similar trace element characteristics (enrichments of LILE and LREE and depletions in HFSE as a common feature of orogenic magmatic rocks), with subtle differences in their Sr-87/Sr-86((i)) ratios (basalts and rhyolites similar to 0.708, dacites similar to 0.710). Most of the samples of the high-MgO SHO-UK group are classified as shoshonite and latite, with some lamproites, sharing similar geochemical features with the other ultrapotassic rocks of the Mediterranean. All the rock groups have similar and high abundances of incompatible trace elements, and radiogenic Sr. Geochemical modeling of the trace element and isotopic ratios of the samples reveals that both the SHO-UK and HKCA groups were derived from a common mantle source which had been highly metasomatized and enriched by continental materials during partial subduction of the crustal metamorphic slices in a continental collision setting. The geochemical variations of these rocks were mainly controlled by source characteristics (such as heterogeneity) and variable degrees of partial melting and subsequent effects of fractional crystallization, with low degrees of crustal contamination. The HKCA series were derived by higher degrees of partial melting of the lithospheric mantle source than the SHO-UK rocks. The HKCA rocks then underwent two-stage fractional crystallization (clinopyroxene-dominated followed by feldspar-dominated fractionating mineral assemblages) to form the high-K calc-alkaline basalt to rhyolite series, whereas the SHO-UK rocks experienced comparatively little fractional crystallization. A tectonic scenario involving the rapidly extending and thinning of orogenic crust is compatible with the time-dependent compositional variation of the magmatic rocks.

Dated peperites associated with ultrapotassic volcanic centres of the Neogene Volcanic Province of southeast Spain are of particular interest within the complex tectonomagmatic context of the Western Mediterranean because they show clear volcano-sedimentary interactions making them a valuable tool for correlating between Miocene sedimentary basins in the region. Detailed field mapping of two coeval, but geographically separate, ultrapotassic volcanic centres (Zeneta and La Aljorra), and comparison of sedimentary facies and radiometric ages with another at Fortuna, suggest that these centres apparently formed at approximately the same time, late Tortonian, by the same tectonomagmatic process, strike-slip, and in the same, shallow marine, paleogeographical context. Stratigraphic indicators in the Miocene basins suggest that basin-closure initiated in the region during the late Tortonian, prior to the main Mediterranean Messinian salinity crisis. Notably, many of the ultrapotassic volcanic centres are situated close to, and elongated along, the basin margins faults. We suggest, therefore, that movement of basin margin faults that closed the Miocene sedimentary basins causing drying out also facilitated the contemporaneous ascent of ultrapotassic magma. So, volcano-sedimentary interactions may be used to make inferences about both the tectonomagmatic and paleogeographic evolution of a region. In southeast Spain peperites provide evidence that the Tortonian 'salinity crisis' was geographically more widespread, extending to the southeast, than previously recognized., This study has been financially supported by the Andalusian grant RNM1595, the Spanish grant CGL2008-02864, and a Masters grant awarded to AC by the Departamento de Mineralogía. y Petrología, Universidad de Granada, Spain.

In the Italian peninsula leucite-free and -bearing ultrapotassic rocks occur intimately associated but well separated in time. Silica-saturated ultrapotassic and associated shoshonitic magmas erupted during the Pliocene to Lower Pleistocene. Silica under-saturated leucite-bearing ultrapotassic rocks, mainly leucitites, were emplaced sometime later, during the Middle–Upper Pleistocene. The transition from leucite-free to -bearing rocks is diachronous and in some cases is complicated by the occurrence of crustal-derived magmas coeval with early leucite-free magma. The Monte Cimino–Vico area is a key locality for studying the transition from leucite-free to -bearing ultrapotassic rocks. There a volcanic complex is overlain by some 500 ka younger leucite-bearing rocks of Vico stratovolcano. Most of the potassic and ultrapotassic rocks of the Monte Cimino volcanic complex are characterised by high Mg-# (66.4–77.8), and compatible element abundances in spite of their high silica contents (52.9–58.0 wt.%). Ultrapotassic leucite-free rocks transitional to lamproites are olivine-bearing orthopyroxene- and plagioclase-free latites and K-rich basaltic trachyandesite and they are confined in the final mafic activity of the Monte Cimino volcanic complex. Two-pyroxene parageneses are observed in the early Monte Cimino volcanic complex giving equilibration temperature as high as 1050 °C and suggesting a sub-crustal derivation of their parental magmas. A two-pyroxene high-K calc-alkaline magma is then inferred for the genesis of the early Monte Cimino activity (e.g. dome complex and silicic lava flows and ignimbrites), which was modelled through crystal-fractionation from a high-K basaltic andesitic magma plus mixing with crustal anatectic rhyolitic magma. Final mafic lavas fill the isotopic and chemical gap between shoshonite-like and lamproite-like rocks, and each lava flow could be considered as a mantle-derived term from a heterogeneous sub-continental lithospheric mantle. Final mafic lavas are high-silica and -MgO ultrapotassic rocks due to crystallisation of primitive magmas generated by partial melting of a vein metasomatised network within a lithospheric upper mantle source, at low pressure and high P H2O . The shift to the younger Vico volcano, in which leucite-bearing magmas prevail, is thought to be due to the arrival in the mantle source of newly formed metasomatic agent from the undergoing slab characterised by the increasing of a sedimentary carbonate recycled component. This new component appears in the Middle Pleistocene and it is responsible for the composition of the magmatism of the Roman region. The recycling of carbonate-bearing pelitic sediments within the mantle wedge produces a carbonate-rich metasomatic agent. The latter is responsible for stabilisation of phlogopite-bearing wehrlitic veins within the mantle wedge. Partial melting of this newly formed vein network under high X CO2 generated silica under-saturated, and then leucite-bearing, ultrapotassic primary melts. A further shift is observed among the Vico post-caldera magmas, in which the appearance of a deep asthenospheric component is argued to be channelled late through slab-tears.

Mineral assemblages of both cognate inclusions and host-lamprophyres with lamproitic affinity in Kocapinar district (Denizli), Western Anatolia, consist of phlogopitic mica, diopsidic clinopyroxene, K-feldspar, apatite, opaque and carbonates (calcite-dolomite). Two distinct types of cognate inclusions have been defined in host lamprophyres: clinopyroxene-rich (CCI) and clinopyroxene-phlogopite-rich (CPCI). Whole-rock compositions of inclusions show a near-primitive nature with high MgO (7.56-15.1 wt.%), Cr (195-2270 ppm), Ni (213-335 ppm) contents and a potassic character [K2O (2.0-2.8 wt.%) > Na2O (0.4-2.2 wt.%)]. Data imply that the inclusions crystallized from magmas formed by melting of phlogopite-bearing pyroxenites in a peri-dotitic mantle source, however, the presence of reverse-zoning in clinopyroxenes with salitic Fe-rich green cores in host-lamprophyres and CPCI inclusions suggest that the Denizli lavas represent mixtures of distinct (probably ultrapotassic and alkali basaltic) magmas. Estimated geobarometric constraints inferred from clinopyroxene compositions in CCI and CPCI inclusions indicate moderate pressures of pyroxene crystallization (ranging between 1.7 and 2.2 GPa and corresponding to 53-70 km depths) under low pressure magma fractionation. Results reveal that i) the origin of Denizli lamprophyres with transitional (between arc-type and intra-plate-type) geochemical signatures is consistent with a shallow level mantle petrogenesis, rather than a deep-seated origin related to mantle convection, ii) the source was a highly refractory and metasomatized peridotitic mantle present at the base of the lower crust, iii) metasomatic agents that affected the mantle lithosphere beneath Denizli region are distinct from those beneath other western Anatolia orogenic centers, and iv) the transitional character of Kocapinar (Denizli) lamprophyric rocks were probably formed as a result of either underplating or contamination of asthenospheric magma at the base of the mantle lithosphere, or assimilation of delaminated continental edge-lithospheric mantle via ascending asthenosphere. Denizli lamprophyres are interpreted to have formed during the formation of a basin/graben structure in the Latest Miocene-Early Pliocene, just after Late Miocene exhumation of Menderes massif. (C) 2012 Elsevier B.V. All rights reserved.

Ultrapotassic plutons from several domains of the Variscan orogenic belt have been in turn interpreted as syn- to post-orogenic due to their age spread, but assessment of their geodynamic setting and source regions is still open to interpretation. In the Svoge region (Bulgaria), at the southern margin of the Balkan orogen, peralkalic plutons are hosted within Ordovician pelites. The main intrusion, with lamproitic affinity, which hosts monzodiorite xenoliths and a polyphase syenite suite, was emplaced at a shallow level.40Ar–39Ar dating by step-heating of amphibole and biotite yielded a Early Carboniferous intrusion age for the main body (337 ± 4 and 339.1 ± 1.6 Ma). The lamproite intrusion is silica-rich compared with bona fide lamproites and characterized by moderate LILE and LaN/YbNenrichments. Sr and Nd isotopic data (initial ϵNdin the range −4.87 to −5.88) suggest an origin in a depleted lithospheric mantle, possibly refertilized by eo-Variscan subduction. The high-K syn-tectonic plutonism in several zones of the Variscan orogen (Bohemian, Austro-Alpine, Vosges, French and Corsica domains) is consistent with a derivation of high-K magmatism from partial melting of metasomatized mantle following the subduction along the collision front between Gondwana and Laurasia.

Centenas de intrusões de natureza kimberlítica ou relacionadas são conhecidas na Província Diamantífera do Alto Paranaíba, em Minas Gerais e Goiás. O pipe Abel Régis, localizado em Carmo do Paranaíba e descoberto pela De Beers na década de 1970, é um desses corpos, que tem sido, em geral, considerado como um kimberlito. Na área da intrusão, ocorrem metassedimentos neoproterozóicos do Grupo Bambuí, os quais são atravessados pelo pipe cretácico (?) de forma superficial aproximadamente circular, com cerca de 1.400 m de diâmetro. Foram distinguidas diversas fácies petrográficas no corpo, que é um dos poucos de toda a província mineral onde encontram-se preservadas feições da zona de cratera. Como o acervo de informações pré-existentes não era esclarecedor quanto à mineralogia de tal corpo, efetuaram-se também estudos com microssonda eletrônica, os quais demonstraram significativas mudanças quanto ao até então admitido. As mais importantes foram: predomínio local de Cr-espinélio sobre ilmenita entre os minerais indicadores, ilmenitas pouco magnesianas e presença abundante do K-feldspato sanidina. Essas características, somadas ao aspecto em forma de taça apresentado pelo corpo, permitem sugerir, em princípio, que a intrusão Abel Régis possa ser de natureza lamproítica. Hundreds of kimberlite or related intrusions are known in the Alto Paranaíba Diamondiferous Province, in the states of Minas Gerais and Goiás. The Abel Régis intrusion, located in Carmo do Paranaíba county is one of these bodies that was discovered in the 1970´s by De Beers, and has generally been recognized as kimberlite. Neoproterozoic metasedimentary rocks of the Bambuí Group are found in the intrusion area. These rocks are cut by the Cretaceous(?) body outcropping as a nearly circular section with 1,400 m in diameter. Distinct petrographic facies, including crater facies, can be recognized in the body. As the previous data was not informative about the mineralogical features of the intrusion, studies were also performed with electron microprobe, which indicated significant changes in relation to the allowed concepts. The most important were: the local predominance of Cr-spinel in relation to ilmenite, Mg-poor ilmenites, and an abundant presence of the K-feldspar sanidine. These characteristics, added to the cup-shaped body, point out that the Abel Régis intrusion could probably present a lamproitic affinity.

High-MgO ultrapotassic rocks are found in four different areas of the Western Mediterranean basin associated in space and time with shoshonitic and calc-alkaline rocks. They represent different magmatic events at the active continental plate margin from Oligocene to Pleistocene. These rocks are found within the Western Alps (Northern Italy), in Corsica (France), in Murcia-Almeria (South-Eastern Spain), and in Southern Tuscany (Central Italy). Ultrapotassic terms are mostly lamprophyres, but olivine latitic lavas with a clear lamproitic affinity are also found. Lamproite-like rocks range from slightly silica under-saturated to silica over-saturated, and they are characterised by low Al(2)O(3), CaO, and Na(2)O contents. They are plagioclase-free rocks, but K-feldspar is abundant beside other K-bearing phases. Shoshonitic and calc-alkaline rocks are invariably space associated to lamproites, and they either precede or follow them. High-Mg ultrapotassic rocks are characterised by strong enrichment of incompatible elements, which prevent further enrichment due to shallow level crustal contamination. K(2)O and incompatible element contents decrease passing from high-Mg ultrapotassic to high-Mg shoshonitic and calc-alkaline rocks suggesting that K(2)O and incompatible trace elements enrichments are a primary characteristic. Ultrapotassic to calc-alkaline rocks from Western Mediterranean regions, in spite of their different age of emplacement, are characterised by similar incompatible trace elements distribution. Depletion of High Field Strength elements with respect to Large Ion Lithophile elements is observed. Positive spikes at Th, U, and Pb, with negative spikes at Ba, Nb, Ta, Sr, P, and Ti, are common characteristics of ultrapotassic (lamproitic) to high-K calc-alkaline rocks. Ultrapotassic rocks are extremely enriched in radiogenic Sr and unradiogenic Nd with respect to the associated shoshonitic and calc-alkaline rocks. Different isotopic values are distinctive of the different magmatic provinces irrespective of magmatic affinities. (87)Sr/(36)Sr(i) ranges between 0.71645 and 0.71759 for Western Alps lamproites, between 0.71226 and 0.71230 for Corsica lamproite, between 0.71642 and 0.72259 for Murcia-Almeria lamproites, and between 0.71578 and 0.71672 for Tuscany lamproites. Radiogenic Sr decreases along with K(2)O through shoshonitic to calc-alkaline rocks. Conversely (143)Nd/(144)Nd(i) values increase with decreasing K(2)O with the highest value of 0.51243 found for the one samples from Murcia-Almeria. Contrasting trends are observed among initial values of lead isotopes, but all falling well within the field of upper crustal rocks. Different trends of (207)Pb/(204)Pb(i) and (208)Pb/(204)Pb(i) VS. (206)Pb/(204)Pb(i) for samples from the different provinces are observed. Several evidences indicate that most of the magmas of the different provinces have been generated in a depleted upper mantle (i.e., lithospheric) modified by metasomatism, but an asthenospheric component is also recognised in Corsica. At least two different subduction-related metasomatic agents re-fertilised the depleted original upper mantle source. Carbonate-free siliciclastic sediments and carbonate-rich sediments have been recycled within the upper mantle through subduction and partial melting. Assuming that metasomatic component is concentrated in a vein network, in Tucany and Corsica, time relationships indicate that low degree of partial melting of the pure vein produced lamproitic-like magmas, whereas an increase in the partial melting involve the surrounding upper mantle, then diluting the alkaline component and produced the entire spectra of magma observed. In South-Eastern Spain calc-alkaline magmatism preceded lamproitic ones, and might be generated by partial melting of mantle wedge metasomatised by fluids from oceanic slab prior to collision. Lamproitic magmas followed after melt-dominated metasomatic agents invaded the lithospheric upper mantle domain. Migration of the magmatism with time is the result of eastward migration of subduction with subsequent opening of Balearic, Ligure-Provencal, and Tyrrhenian basins. (C) 2008 Elsevier B.V. All rights reserved.

High-MgO ultrapotassic rocks are found in four different areas of the Western Mediterranean basin associated in space and time with shoshonitic and calc-alkaline rocks. They represent different magmatic events at the active continental plate margin from Oligocene to Pleistocene. These rocks are found within the Western Alps (Northern Italy), in Corsica (France), in Murcia-Almeria (South-Eastern Spain), and in Southern Tuscany (Central Italy). Ultrapotassic terms are mostly lamprophyres, but olivine latitic lavas with a clear lamproitic affinity are also found. Lamproite-like rocks range from slightly silica under-saturated to silica over-saturated, and they are characterised by low Al2O3, CaO, and Na2O contents. They are plagioclase-free rocks, but K-feldspar is abundant beside other K-bearing phases. Shoshonitic and calc-alkaline rocks are invariably space associated to lamproites, and they either precede or follow them. High-Mg ultrapotassic rocks are characterised by strong enrichment of incompatible elements, which prevent further enrichment due to shallow level crustal contamination. K2O and incompatible element contents decrease passing from high-Mg ultrapotassic to high-Mg shoshonitic and calc-alkaline rocks suggesting that K and incompatible trace elements enrichments are a primary characteristic. Ultrapotassic to calc-alkaline rocks from Western Mediterranean regions, in spite of their different age of emplacement, are characterised by similar incompatible trace elements distribution. Depletion of High Field Strength elements with respect to Large Ion Lithophile elements is observed. Positive spikes at Th, U, and Pb, with negative spikes at Ba, Nb, Ta, Sr, P, and Ti, are common characteristics of ultrapotassic (lamproitic) to high-K calc-alkaline rocks. Ultrapotassic rocks are extremely enriched in radiogenic Sr and unradiogenic Nd with respect to the associated shoshonitic and calc-alkaline rocks. Different isotopic values are distinctive of the different magmatic provinces irrespective of magmatic affinities. 87Sr/86Sri ranges between 0.71645 and 0.71759 for Western Alps lamproites, between 0.71226 and 0.71230 for Corsica lamproite, between 0.71642 and 0.72259 for Murcia-Almeria lamproites, and between 0.71578 and 0.71672 for Tuscany lamproites. Radiogenic Sr decreases along with K2O through shoshonitic to calc-alkaline rocks. Conversely 143Nd/144Ndi values increase with decreasing K2O, with the highest value of 0.51243 found for the one samples from Murcia-Almeria. Contrasting trends are observed among initial values of lead isotopes, but all falling well within the field of upper crustal rocks. Different trends of 207Pb/204Pbi and 208Pb/204Pbi vs. 206Pb/204Pbi for samples from the different provinces are observed. Several evidences indicate that most of the magmas of the different provinces have been generated in a depleted upper mantle (i.e., lithospheric) modified by metasomatism, but an asthenospheric component is also recognised in Corsica. At least two different subduction-related metasomatic agents re-fertilised the depleted original upper mantle source. Carbonate-free siliciclastic sediments and carbonate-rich sediments have been recycled within the upper mantle through subduction and partial melting. Assuming that metasomatic component is concentrated in a vein network, in Tuscany and Corsica, time relationships indicate that low degree of partial melting of the pure vein produced lamproitic-like magmas, whereas an increase in the partial melting involve the surrounding upper mantle, then diluting the alkaline component and produced the entire spectra of magma observed. In South-Eastern Spain calc-alkaline magmatism preceded lamproitic ones, and might be generated by partial melting of mantle wedge metasomatised by fluids from oceanic slab prior to collision. Lamproitic magmas followed after melt-dominated metasomatic agents invaded the lithospheric upper mantle domain. Migration of the magmatism with time is the result of eastward migration of subduction with subsequent opening of Balearic, Ligure-Provençal, and Tyrrhenian basins.

The central-western Mediterranean is one of the most important areas on Earth for studying subduction-related potassic and ultrapotassic magmatism. In the circum-Tyrrhenian area leucite-free (i.e., lamproite) and leucite-bearing (i.e., kamafugite, leucitite, and plagioleucitite) ultrapotassic rocks have been emplaced and are associated with shoshonites and high-K calc-alkaline volcanic rocks. Four different magmatic provinces are recognised from this area. Eastward and then south-eastward migration of magmatism with time occurred following roll-back of the subducting plate. Leucite-free silica-rich lamproites are restricted to the early stages of magmatism, associated with shoshonites and high-K calc-alkaline volcanic rocks. Present day volcanic activity is restricted to the Neapolitan district where ultrapotassic rocks with variable geochemical and isotopic characteristics occur. Ultrapotassic rocks are strongly enriched in incompatible trace elements with variable fractionation of Ta, Nb, and Ti with respect to Th and large ion lithophile elements. Mafic ultrapotassic rocks are also variably enriched in radiogenic Sr and Pb and unradiogenic Nd. The main geochemical and isotopic signatures result from sediment recycling within the upper mantle via subduction. Selected trace element ratios suggest that high temperatures are required to generate sediment-derived melts. Recycling of carbonated pelites play an important role in the Roman province controlling the genesis of leucite-bearing magmas. Large volumes of metasomatic components are predicted to be accommodated within a vein network in the sub-continental lithospheric mantle. Partial melting of the pure vein mineralogy is likely to generate ultrapotassic magmas of either lamproitic or kamafugitic nature. Over time, increased interaction between the metasomatic vein lithology and the surrounding mantle dilutes the alkaline component producing shoshonites and high-K calc–alkaline rocks. The addition of a further subduction-related component shortly before magma generation is required to explain the isotopic composition of rocks from the Neapolitan district. In the last phases of circum-Tyrrhenian evolution, a within-plate component appears within south-eastern Italy. This component is evident at Vulture volcano, in the Lucanian Magmatic province (SE Italy).

ÖZET Afyon volkanik compleksinin Sandıklı-Şuhut çizgisi güneyinde kalan bölgede genel olarak üç farklı kaya grubu yüzlek vermektedir. Bu kaya grupları, 1. Temelli oluşturan Toros kuşağı sedimanter kayalarından, 2. bileşimler orarak geniş komposizyon ve lav fasiyesleri sunan volkanik kayalardan, 3. volkanoklastic kayalardan ve 4, gölsel sedimanter kayalardan oluşmaktadır. Farklı volkanik aktivitenin ürünleri olan volcanik kayalar Batı Toroslarann kuzeybatısında gözlenen kaim bir seri sunan kireçtaşılan ile ardalanmalı kumtaşlan, silttaşı, kiltaşı, şeyi ve çamurtaşından oluşan yastık lav düzeyleri ve diyabaz blokları içeren sedimanter kaya topluluğunu kesmekte ve/veya örtmektedirler. Geniş alanlarda yaydım sunan üç grup volkanoklastik seri bölgede etkin olan üç farklı volkanik aktiviteyi temsil etmektedir. (1) Lösitit blok ve kınntüannca zengin Balçıkhisar volkanoklastik seri bölgerde etkin olan ilk volkanik faaliyetin ürünlerini örmektedir. (2) Oldukça geniş yaydım sunan ve birden fazla evrede oluşmuş piroklastik akmalar, kül yağmalan ile lav bloklarından meydana gelen Başören piyroklastik serisinin ilk ürünleri Balçıkhisar volkanoklastik seri tarafından kısmen örtülmektedir. Fakat, Başören piroklastik serinin ilerki aşamalarına ait piroklastik kayalar Balçıkhisar volkanoklastiklerini üzerlemektedirler. (3) Balçıkhisar volkanoklastik serisi, Başören piroklastik serisi ve gölsel ortama ait sedimanter kayalar üçüncü evre volkanik faaliyeti ayırt eden Tokluk volkanosedimanter serisi tarafindan örtülmektedir. Balçıkhisar volkanoklastik serisinin içinde yaygın olarak bulunan ve genel olarak klinopiroksen - flogopit - melanit - melilit - lösit - perovskit - ilmenit - apatitden oluşan mineral bileşimine sahip ksenolitler volkanoklastik seri için ayırtedici bir özelliğe sahiptir. vnBölgede yer alanlar gölsel sedimanlar, kireçtaşı, kiltaşı, kumtaşı ve çakdtaşı ardalanmasından oluşmaktadır ve Başören piroklastik seri ile Balçıkhisar volkanoklastik serisini örtmektedirler. Gölsel sedimanter kayalar dereceli olarak üste doğru volkanosedimanterlere geçiş sunmaktadır. Geniş olarak bileşimsel farlılıklar ve lav fasiyesleri sunan volkanik kayalar stratigrafik ilişkilerine göre olarak üç gruba ayrılmaktadır. Lösitit, tefrifonolitle ve benekli trakiandezit lavları ilk volkanik faaliyetin ürünleridir ve Balçıkhisar volkaniklastik seri tarafindan örtülmektedir. İkinci volkanik faaliyete ait ürünler kendi piroklastiklerinİ kesen ve/veya örten trakiandezitik lav dondan, subvolkanik stoklar ile yanal olarak fazla yaydım sunmayan lav akmalarından oluşmaktadır. Lamproitik dayklar-domlar ve lav akmaları bölgedeki ikinci volkanik faaliyetin ilk ürenlerinden olup Başören piroklastik serinin ilk ürünleri içine sokulmuşlardır ve lav akmalın de kısmen örtülmüşlerdir. Bölgede gözlenen lamproitik lava akmaları, Başören piroklastik serinin derki aşamasına ait piroklasikler de Balçıkhisar volkanoklastik serisine ait kayalar tarafindan örtülmüşlerdir. Bölgede etkin olan son volkanik faaliyet fonotefrit, fonolit, bazaltik trakiandeziti ve nosean içeren trakiandeziti lav dondan, dayklan ve aklamaları de temsd edilmektedir. Fonotefritlerin lava dondan ve dayklan sırasıyla Balçıkhisar volkaniklastiklerini, gölsel kireçtaşlannı ve Tokluk volkanosedimanterlerini kesmekte ve örtmektedirler. Hacimsel olarak küçük bir alan kaplayan nosean içerikli trakiandezit lav domu Balçıkhisar volkaniclastik serisini kesmekte ve kısmende örtmektedir. Jeokimyasal ve petrografik veriler kapsamında volkanik kayalar, silisçe aşındoygun, silice doygun ve silice doğun olmayan şeklinde üç ana gruba ayrılmıştır. Başören trakiandezit, nosean içerikle trakiandezit, tefrifonolit, fonolit ve lamproitler silisçe aşındoygun grupta yeraJmaktadır. Silisçe doygun olardan benekli traMandezitler de bazalitik trakiandezitler oluşturmaktadır. Fonotefrit ve lösititler silisçe doygun olmayan gruptadır. Volkanik kayalar genelde yüksek potasyumlu ve baskın bir şekilde alkalen özelliktedirler. İlksel alkalen magmanın geliştiği tektonik ortam ve kaynağı Afrika plakasının Avrupa plakası altına dalmasını takip eden aşamada meydana gelen çarpışma süreciyle ilgilidir. Bölgede yeralan potasik alkalen vuımagmanın oluşumunu açıklayan iki farklı olasılık sözkonusudur. İlk olasılık, fraksiyonal kristalleşme île değişken oranda farklı derecelerde bölümsel ergimeye uyramış tek bir kaynağın varlığıdır. İkinci olasılık iki farklı kaynağın varoluşudur. Lösitit, tefrifonolit ve fonolitleri oluşturan birinci ilksel kaynak, özümsenmiş fraksiyonal kristalizasyonun (üst kabuk malzemesinin katılması) takip ettiği bölümsel ergime süreci ile oluşmuştur. Fonotefrit, bazaltik trakiandezit ve nosean içeren bazaltik trakiandezit oluşturan ikinci kaynak ise bölümsel ergime ve özümsenmiş fraksiyonal kristalizasyonun süreci ile (pelajik sediment katılımı) veya zenginleşmiş bir kaynağın bölümsel ergimesi ile meydana gelmiştir. Balçıkhisar volkaniklastik seri içine mekanik yollarla gelmiş olan üst manto kökenli ksenolitler ve ksenokristaller potasik ve ultra potasik magmanın kaynağının manto metasomatizması olduğunu bildiren habercilerdir. ıx ÖZET Afyon volkanik compleksinin Sandıklı-Şuhut çizgisi güneyinde kalan bölgede genel olarak üç farklı kaya grubu yüzlek vermektedir. Bu kaya grupları, 1. Temelli oluşturan Toros kuşağı sedimanter kayalarından, 2. bileşimler orarak geniş komposizyon ve lav fasiyesleri sunan volkanik kayalardan, 3. volkanoklastic kayalardan ve 4, gölsel sedimanter kayalardan oluşmaktadır. Farklı volkanik aktivitenin ürünleri olan volcanik kayalar Batı Toroslarann kuzeybatısında gözlenen kaim bir seri sunan kireçtaşılan ile ardalanmalı kumtaşlan, silttaşı, kiltaşı, şeyi ve çamurtaşından oluşan yastık lav düzeyleri ve diyabaz blokları içeren sedimanter kaya topluluğunu kesmekte ve/veya örtmektedirler. Geniş alanlarda yaydım sunan üç grup volkanoklastik seri bölgede etkin olan üç farklı volkanik aktiviteyi temsil etmektedir. (1) Lösitit blok ve kınntüannca zengin Balçıkhisar volkanoklastik seri bölgerde etkin olan ilk volkanik faaliyetin ürünlerini örmektedir. (2) Oldukça geniş yaydım sunan ve birden fazla evrede oluşmuş piroklastik akmalar, kül yağmalan ile lav bloklarından meydana gelen Başören piyroklastik serisinin ilk ürünleri Balçıkhisar volkanoklastik seri tarafından kısmen örtülmektedir. Fakat, Başören piroklastik serinin ilerki aşamalarına ait piroklastik kayalar Balçıkhisar volkanoklastiklerini üzerlemektedirler. (3) Balçıkhisar volkanoklastik serisi, Başören piroklastik serisi ve gölsel ortama ait sedimanter kayalar üçüncü evre volkanik faaliyeti ayırt eden Tokluk volkanosedimanter serisi tarafindan örtülmektedir. Balçıkhisar volkanoklastik serisinin içinde yaygın olarak bulunan ve genel olarak klinopiroksen - flogopit - melanit - melilit - lösit - perovskit - ilmenit - apatitden oluşan mineral bileşimine sahip ksenolitler volkanoklastik seri için ayırtedici bir özelliğe sahiptir. vnBölgede yer alanlar gölsel sedimanlar, kireçtaşı, kiltaşı, kumtaşı ve çakdtaşı ardalanmasından oluşmaktadır ve Başören piroklastik seri ile Balçıkhisar volkanoklastik serisini örtmektedirler. Gölsel sedimanter kayalar dereceli olarak üste doğru volkanosedimanterlere geçiş sunmaktadır. Geniş olarak bileşimsel farlılıklar ve lav fasiyesleri sunan volkanik kayalar stratigrafik ilişkilerine göre olarak üç gruba ayrılmaktadır. Lösitit, tefrifonolitle ve benekli trakiandezit lavları ilk volkanik faaliyetin ürünleridir ve Balçıkhisar volkaniklastik seri tarafindan örtülmektedir. İkinci volkanik faaliyete ait ürünler kendi piroklastiklerinİ kesen ve/veya örten trakiandezitik lav dondan, subvolkanik stoklar ile yanal olarak fazla yaydım sunmayan lav akmalarından oluşmaktadır. Lamproitik dayklar-domlar ve lav akmaları bölgedeki ikinci volkanik faaliyetin ilk ürenlerinden olup Başören piroklastik serinin ilk ürünleri içine sokulmuşlardır ve lav akmalın de kısmen örtülmüşlerdir. Bölgede gözlenen lamproitik lava akmaları, Başören piroklastik serinin derki aşamasına ait piroklasikler de Balçıkhisar volkanoklastik serisine ait kayalar tarafindan örtülmüşlerdir. Bölgede etkin olan son volkanik faaliyet fonotefrit, fonolit, bazaltik trakiandeziti ve nosean içeren trakiandeziti lav dondan, dayklan ve aklamaları de temsd edilmektedir. Fonotefritlerin lava dondan ve dayklan sırasıyla Balçıkhisar volkaniklastiklerini, gölsel kireçtaşlannı ve Tokluk volkanosedimanterlerini kesmekte ve örtmektedirler. Hacimsel olarak küçük bir alan kaplayan nosean içerikli trakiandezit lav domu Balçıkhisar volkaniclastik serisini kesmekte ve kısmende örtmektedir. Jeokimyasal ve petrografik veriler kapsamında volkanik kayalar, silisçe aşındoygun, silice doygun ve silice doğun olmayan şeklinde üç ana gruba ayrılmıştır. Başören trakiandezit, nosean içerikle trakiandezit, tefrifonolit, fonolit ve lamproitler silisçe aşındoygun grupta yeraJmaktadır. Silisçe doygun olardan benekli traMandezitler de bazalitik trakiandezitler oluşturmaktadır. Fonotefrit ve lösititler silisçe doygun olmayan gruptadır. Volkanik kayalar genelde yüksek potasyumlu ve baskın bir şekilde alkalen özelliktedirler. İlksel alkalen magmanın geliştiği tektonik ortam ve kaynağı Afrika plakasının Avrupa plakası altına dalmasını takip eden aşamada meydana gelen çarpışma süreciyle ilgilidir. Bölgede yeralan potasik alkalen vuımagmanın oluşumunu açıklayan iki farklı olasılık sözkonusudur. İlk olasılık, fraksiyonal kristalleşme île değişken oranda farklı derecelerde bölümsel ergimeye uyramış tek bir kaynağın varlığıdır. İkinci olasılık iki farklı kaynağın varoluşudur. Lösitit, tefrifonolit ve fonolitleri oluşturan birinci ilksel kaynak, özümsenmiş fraksiyonal kristalizasyonun (üst kabuk malzemesinin katılması) takip ettiği bölümsel ergime süreci ile oluşmuştur. Fonotefrit, bazaltik trakiandezit ve nosean içeren bazaltik trakiandezit oluşturan ikinci kaynak ise bölümsel ergime ve özümsenmiş fraksiyonal kristalizasyonun süreci ile (pelajik sediment katılımı) veya zenginleşmiş bir kaynağın bölümsel ergimesi ile meydana gelmiştir. Balçıkhisar volkaniklastik seri içine mekanik yollarla gelmiş olan üst manto kökenli ksenolitler ve ksenokristaller potasik ve ultra potasik magmanın kaynağının manto metasomatizması olduğunu bildiren habercilerdir. ıx 274

Not available, Le but de cette étude est de rechercher la source primaire du diamant des alluvions de la zone de Makongonio, Gabon, en étudiant les minéraux lourds de celles-ci. Elle comprend donc une introduction aux gisements primaires et secondaires de diamant. Puis une première partie consacrée aux généralités sur les kimberlites et les lamproites, sources primaires terrestres de diamant naturel connues. Enfin une deuxième partie qui traite de l'étude des échantillons des minéraux lourds provenant de Makongonio, des méthodes analytiques utilisées et des résultats obtenus. Cette étude révèle la présence des minéraux satellites tels que l'ilménite magnésienne, les spinelles chromifères, les zircons, l'olivine et la chlorite. Un cortège minéralogique qu'on trouve dans les kimberlites ou les lamproites, roches d'où pourrait provenir ce diamant

Not available, Le but de cette étude est de rechercher la source primaire du diamant des alluvions de la zone de Makongonio, Gabon, en étudiant les minéraux lourds de celles-ci. Elle comprend donc une introduction aux gisements primaires et secondaires de diamant. Puis une première partie consacrée aux généralités sur les kimberlites et les lamproites, sources primaires terrestres de diamant naturel connues. Enfin une deuxième partie qui traite de l'étude des échantillons des minéraux lourds provenant de Makongonio, des méthodes analytiques utilisées et des résultats obtenus. Cette étude révèle la présence des minéraux satellites tels que l'ilménite magnésienne, les spinelles chromifères, les zircons, l'olivine et la chlorite. Un cortège minéralogique qu'on trouve dans les kimberlites ou les lamproites, roches d'où pourrait provenir ce diamant

Members of the roedderite-chayesite series in lamproites from Cancarix (SE Spain), crystallized from late magmatic residua under low PH2O, high temperature (∼ 1100°C), oxidizing conditions. They exhibit the following main chemical variations: 0.14 ⩽ Na ⩽ 0.62 atoms per formula unit (apfu); 0.80 ⩽ K⩽ 1.00 apfu; 2.97 ⩽ Mg ⩽ 4.33 apfu; 0.00 ⩽ Fe2+ ⩽ 1.19 apfu; 0.42 ⩽ Fe3+ ⩽ 0.87 apfu; they are hexagonal (10.120 ⩽ a ⩽ 10.135 Å, 14.305 ⩽ c ⩽ 14.326 Å), P6/mcc. The characteristic chemical substitution is: Fe3+ + □ ⇌ Fe2+ + (K+Na)+. Six crystal structures have been refined to 0.020 ⩽ Robs ⩽ 0.026. They have the osumilite/milarite-type structure, with Si entering the double tetrahedral T1 six-membered rings, and Mg and Fe entering both the ring-linking T2 tetrahedra, and the A octahedra. The 12-coordinated C site, located between two double rings of T1 tetrahedra, is occupied mainly by K and subordinately by Na. Furthermore, Na occupies the partially empty nine-fold coordinated B site which occurs both in the ideal (z = 0) and in a split-atom position along the c direction.

The type kajanite is a leucite-bearing rock. Its chemical composition is close to that of lamproites or lamprophyres on the basis of the Al2O3, TiO2 and K2O contents as well as Mg/(Mg+Fe) and (Na+K)/Al ratios. Nevertheless kajanite is not peralkaline in composition, and K2O/Na2O ratio is lower than generally found in lamproites. Similarities and differences with typical lamproites are also apparent in the mineralogicai composition : the presence of olivine (with Cr-spinel inclusions), phlogopite, leucite and richterite is in agreement with lamproite definition, but the composition of richterite and Cr-spinels is more aluminous. Groundmass oxides are Ti-magnetites unlike typical lamproites which contain Ti-rich oxides (ilmenite and/or pseudobrookite). In spite of apparent similarities, this detailed study indicates that kajanite is indeed not a typical lamproite but its character places it close to the lamproite group of rocks., La kajanite est une roche potassique à leucite dont la composition chimique est proche de celle des lamproïtes ou des lamprophyres si l'on considère les teneurs en Al2O3, TiO2 et K2O ainsi que les rapports Mg/(Mg+Fe) et (Na+K)/Al. Cependant la kajanite n'est pas hyperalcaline et le rapport K2O/Na2O est plus faible que celui trouvé dans les lamproïtes. Ressemblances et différences avec les lamproïtes typiques se retrouvent dans la composition minéralogique : la présence d'olivine (à inclusions de spinelles chromiferes), phlogopite, leucite et richtérite est caractéristique des lamproïtes, mais la composition de la richtérite et des chromites est plus alumineuse. Les oxydes présents (Ti-magnétite) sont différents de ceux des lamproïtes généralement riches en titane. Malgré des similitudes apparentes, cette étude minéralogique détaillée montre donc que la kajanite ne doit pas être placée dans le groupe des lamproïtes typiques mais qu'elle est par tous ses caractères — et comme les cocites — proche des laves de ce groupe., Wagner Christiane. Mineralogy of the type kajanite from Kalimantan. Similarities and differences with typical lamproites. In: Bulletin de Minéralogie, volume 109, 5, 1986. pp. 589-598.

The Lentiira-Kuhmo-Kostomuksha triangle, along the Finland – Russian border and within the central part of the Archean Karelian craton, contains numerous examples of phlogopite-rich, ultramafic, mantle-xenocryst-bearing and, in some cases, diamond-bearing dike rocks. Laser probe Ar-Ar data on phlogopite from 3 dike rocks on the Finnish side (Lentiira, Kuhmo) all gave ages within error of each other, 1202 ± 3 Ma (2σ), 1199 ± 3 Ma (2σ) and 1204 ± 4 Ma (2σ) while a fourth sample produced mixed ages. Published Rb-Sr dates on mineralogically and chemically similar dikes from the Russian side (Kostomuksha) are 1232 ± 5 Ma. The question remains open whether these represent two distinct age populations or whether differences in isotopic system behavior are the reason for the 30 m.y. age difference.