Search

Deep, carbonate-rich melts are key constituents of kimberlites and are crucial for understanding the cycle of volatile elements in the mantle. On the Siberian craton, the Udachnaya-East kimberlite hosts extremely well-preserved nodules composed of chlorides + carbonates + sulfates, that do not present any relict sedimentary textures. These salty nodules display textures that are commonly observed in quenched liquids and may thus represent the very last stage liquid of the kimberlite. Alternatively, they could represent assimilated sedimentary material, or even post-magmatic hydrothermal alteration, because kimberlites are known to ascend through the lithosphere while assimilating material from their wall rocks. Here we focus specifically on those chloride-carbonate nodules, which are composed of 70% chloride + 30% alkali-carbonate and sulfate, and used two radiogenic systems (Rb-Sr, Sm-Nd) and the isotopic composition of sulfur, in addition to their major and trace element compositions (n = 3). We then compared the results with the same geochemical data on host kimberlites (n = 4), sedimentary cover (n = 3) and hydrothermal veins (n = 3). Taken together, our results show that the nodules are not the product of a contamination by the Cambrian sedimentary cover. Trace element patterns of the nodules display extreme enrichments in the same elements that are relatively depleted in the host kimberlite but also in kimberlites worldwide (K, Rb, Sr, Pb), suggesting that chloride-carbonate nodules are snapshots of the latest stage liquid present in the kimberlite system. Their isotopic compositions (Rb-Sr, Sm-Nd and δ34S) are consistent with a common magmatic source with their host kimberlite. We propose that chloride-carbonate nodules record a missing compositional endmember, which could explain the trend towards more radiogenic Sr isotope ratios at nearly constant Nd signatures observed in their host kimberlite, as well as in other kimberlites worldwide. This observed trend suggests the presence of a recycled component with high Rb/Sr (such as salts or terrigenous sediments) in the mantle sampled by some kimberlites, either in the lithosphere or the asthenosphere. This study highlights that the role of alkalies and halogens may have been underestimated in the genesis of kimberlites at depths where diamonds are stable, as well as in more evolved magmatic stages. Segregations of chlorides and carbonates occur specifically in sulfate-bearing kimberlites, which may thus sample a mantle domain in which sulfates with δ34S > 0‰ are dominant. The existence of such a reservoir could explain the apparent imbalance observed between the chondritic value (δ34S of 0‰) and the negative S isotopic compositions of mantle sulfides (MORB and peridotites).

Introduction: The Metegero-Ichersky aquifer forms 90% of the total volume of drainage water in the section of the mining of the main deposits of the Mirny kimberlite field, the Internationalnaya and the Mir pipes. The reservoirs of the Metegero-Ichersky aquifer are also used for the re-injection of brine into the Earth's interior. For this reason, the study of changes in the filtration characteristics of this area within the overall Mirny kimberlite field is an important goal that has to be achieved for the full development of the Internationalnaya and Mir deposits to the full depth of the discovered reserves. Methodology: To study the filtration characteristics and to calculate the water permeability coefficient, we conducted calculations and analysis throughout the entire observation network that consisted of 131 wells. We used observations from monitoring that was performed as well as the results of single and cluster pumping tests performed over the past 20 years. We processed and analysed over 500 groundwater inflow tests and over 50 thousand groundwater level surveys performed throughout the entire regime network. Results and discussion: As a result, we obtained information on the changes in the water permeability coefficient within the studied area. A brief hydrogeological description of the Metegero-Ichersky aquifer and the circulating natural brines was presented. We created a map of the changes in the water permeability coefficient. We studied the aspects and special features of the influence of tectonic disturbances on the hydrodynamic and capacity properties of the reservoirs of the Metegero-Ichersky aquifer. Areal zoning was performed, and individual zone blocks were defined. Conclusions: The conducted work allowed studying the changes in the coefficient of water permeability within the Mirny kimberlite field and to specify the hydrogeological conditions of the area. The dynamic effect of deep faults leads to the formation of an increased fissure displacement of the rocks in the area of study. It is related to multiple tectonic disturbances producing feathering and it leads to the formation of linear zones with increased filtration parameters. The identified pattern is taken into account during the construction of re-injection sites as well as during their expansion, when boring new wells, and searching for additional promising re-injection areas.

Kimberlite pipes are difficult to investigate due to their vertical orientation, conic shape and diverse physical characteristics and petrological compositions, all of which obstruct the use of magnetic methods, reflection and refraction seismic surveys to examine kimberlite pipes. Wherein the emplacement model for kimberlite pipes has important significance in resource geology and in mine design process. As a result, the development of new methods of investigating kimberlite pipes remains necessary. To that end, because the most stable characteristic of kimberlite pipes is their downward-tapering structure, the pipes can be more effectively examined by using methods offering high resolution and new indicators for prospecting. Herein, we present the results of jointly using passive seismic and radiometric methods to study the structure of a kimberlite pipe and its enclosing environment. In particular, we employed a microseismic sounding method, passive seismic interferometry, the H/V method, gamma spectrometry and emanation mapping to model the kimberlite pipe named after M. Lomonosov of the Arkhangelsk diamondiferous province. The combined use of those methods revealed an ore-controlled fault and probably a supply channel (i.e. dyke). The obtained model is correspondent to drill whole data and includes additional information about the structure and elastic properties of the studied pipe. Amongst its principal benefits, the proposed technique affords the possibility of discerning the primary elements of the kimberlite pipes and enclosing environments at depths from 30 m to 2 km, which can significantly increase the effectiveness of investigations into kimberlite pipes.

Mantle xenoliths from the Middle-Late Jurassic Obnazhennaya kimberlite are often compared with those from the Udachnaya kimberlite (ca. 367 Ma) to inform the evolution of the Siberia craton. Howeve...

Olivine is the most common rock-forming mineral of the majority of the lithospheric mantle rocks beneath ancient cratons. This study provides the information about an epigenetic olivine in a lherzolite xenolith from the Udachnaya kimberlite pipe (Siberian craton), which is characterized by lower Mg# compared to the rock-forming one (Mg# = 87.4). The iron-rich olivine has been observed in the epigenetic mineral assemblage that forms a kelyphite shell around the rock-forming garnet. Olivine from the kelyphite shell occurs as both homogeneous grains (Mg# = 84.3–85.9) and zoned grains (Mg# = 85.1–87.5). The major and minor elements asymmetric zoning patterns have been found in the rock-forming olivine grains at the contact with the kelyphite shell. These olivine grains have an outer low Mg# (up to 85.9) zone at the contact with the kelyphite shell as the epigenetic olivine grains in the kelyphite shell. We suggest that the iron-rich epigenetic olivine was produced as the result of a reaction between the rock-forming garnet and the primitive kimberlite melt. During this reaction, a hybrid melt was formed in the interstitial space. The hybrid melt was iron-enriched relative to the kimberlite melt. The source of iron for the micro-portions of the interstitial hybrid melt was the rock-forming garnet.

Comprehensive studies of peridotitic xenoliths from the Udachnaya kimberlite (Yakutian diamond province, Siberian craton) confirm that garnet shows inverse correlation of its volumetric percentage with its Cr2O3 contents in refertilizated peridotites, but no such correlation is observed in depleted peridotites. The correlation relationship plots as an isosceles hyperbola, which is consistent with the existing knowledge of origin of refertilized peridotite. The bulk content of aluminum is proportional to the garnet percentage both in depleted and refertilized peridotites, but Al2O3 in the rock correlates with Cr2O3 in garnet only in the refertilized varieties, while the two parameters are independent in depleted mantle rocks. According to the modeling of refertilization-related composition changes in the Udachnaya peridotites, garnet percentages are directly proportional to the amount of clinopyroxene (Gnt = 0.879*Cpx + 0.022, R2 = 0.78) and inversely proportional to that of olivine (Gnt = 0.026/Ol3.141, R2 = 0.79). As the shares of Gnt and Cpx increase from minimum values, orthopyroxene first increases (to 0.16) and then decreases since 0.65 Ol, 0.09 Cpx, and 0.10 Gnt. This model can constrain the place of the parent rock in the refertilization series knowing Cr2O3 contents in separate garnet grains. The average refertilization degree of lithospheric mantle in the region estimated from the compositions of more than 800 garnet xenocrysts in the Udachnaya kimberlite is expressed in the rock modal composition as: Ol = 0.72, Opx = 0.15, Gnt = 0.07, and Cpx = 0.06 (median values).

Although irrefutable evidence for the presence of signs of diamondiferous kimberlite on the Taimyr Peninsula were obtained in the 1930s, it was only in 2020 that a macrodiamond (>1 mm) was first discovered in Eastern Taimyr. This was a colorless laminar crystal of a transitional shape from an octahedron to a rhombododecahedron. According to the set of features, the crystal is rare and atypical of the known primary and alluvial deposits of the Siberian Diamond Province. The find of this diamond indicates the presence of primary sources and the need for medium-scale geological survey and exploration over a large area from Anabar Bay (Pronchishchev Ridge) to the west to the Kiryaka–Tas and Tulai–Kiryaka highlands and to the northeast to Tsvetkov Cape.

The grade and morphological character of kimberlite-hosted diamonds were compared to crystallization temperature (T) and oxygen fugacity (fO2) estimated from groundmass spinels in six kimberlite pipes in the North China Craton (NCC). Crystallization temperatures calculated at an assumed pressure of 1 GPa are in the range of 1037–1395 °C, with a mean of 1182 °C. At these temperatures, the estimated fO2 varies from 1.2 to 3.1 log units below the nickel-nickel oxide (NNO) buffer. Generally, individual kimberlite pipe shows a small variation of the T (50–100 °C) and fO2 (0.4–0.6 log units), whereas different kimberlite pipes present great changes of T and fO2 which can be up to 300 °C and 2 units respectively. The fO2 of kimberlite magma shows a strong negative correlation with the diamond grade of kimberlite, suggesting that the fO2 plays an important role in diamond resorption, whereas the T shows no relationship with the diamond grade, indicating the T plays no role in diamond resorption. The conditions of kimberlite crystallization (fO2) can be a useful parameter in evaluating diamond survival in diamond exploration.

––A dike of rock similar in composition to carbonatites has been found in the Aikhal diamondiferous pipe of the Alakit–Markha field of the Yakutian kimberlite province (YaKP). The fine-grained rock of essentially carbonate composition (dolomite and calcite) rich in thin-platy phlogopite contains minerals typical of carbonatites: monazite, baddeleyite, and pyrochlore. In the high contents and distribution of incompatible elements the rock differs significantly from kimberlites and is transitional from kimberlites to carbonatites. The content of incompatible elements in this rock is 3–5 times lower than that in carbonatite breccias of the pipes in the Staraya Rechka kimberlite field of the YaKP (Nomokhtookh site). The compositions of accessory trace element minerals from the Aikhal dike rock and the Nomokhtookh carbonatite breccias are compared. An assumption is made that the high contents of incompatible elements in the carbonatite-like rock, which caused the crystallization of accessory minerals, are due to the differentiation of kimberlite melt/fluid. The high Sr isotope ratios indicate that the rock altered during hydrothermal and metasomatic processes. The obtained data on the composition of the carbonatite-like rock cannot serve as an argument for the genetic relationship between the Aikhal kimberlites and typical carbonatites. The genetic relationship between kimberlites and carbonatites in the northern fields of the YaKP remains an open issue.

Zircon xenocrysts from two diamond-barren kimberlite pipes (Leningrad and Ruslovaya) in the West Ukukit kimberlite field opened a ‘window’ to the buried crustal basement in the northern Siberian cr...

Sulfide-bearing polymineralic inclusions in mantle-derived chromium pyrope garnets of lherzolite paragenesis from lamprophyres of the Chompolo field (Aldan shield, southern Siberian craton) have been studied. The inclusions are composed of either only sulfides or sulfides in association with other minerals (carbonates, silicates, oxides, etc.). The sulfide part of the inclusions is represented by up to four minerals. Among the sulfides, minerals rich in Cu and Ni have been found, whereas Fe sulfides (pyrrhotite, troilite) are absent. This distinguishes the inclusions studied from the majority of sulfide inclusions in mantle minerals and diamonds, as well as in mantle xenoliths from kimberlites. The formation of polymineralic inclusions in chromium garnets of the Chompolo field is attributed to the effect of a carbonate–silicate metasomatic melt/fluid on mantle peridotites, as evidenced by the mineral suite associated with the sulfides. The research results indicate significant differences in the nature of metasomatic processes that occurred in the lithospheric mantle of the southern and central parts of the Siberian craton.

In the poorly studied southeastern part of the Chetlas uplift, ring structures typical for magmatic pipe-type bodies (diatremes) have been established. The main part of the ring structures is located in the areas of the distribution of the Upper Devonian sediments. This fact indicates the lower age threshold of the formation of the objects forming them as Late Devonian, i.e., similar to the age of kimberlites of the Arkhangelsk diamond-bearing province. To assess the prospects of one of the most numerous groups of the ring structures, heavy-mineral concentrate sampling of the modern stream sediments was conducted. While studying the heavy-mineral concentrates, chromium-bearing pyrope—a kimberlite indicator mineral—was revealed, and the first diamond grain was found. About 20% of pyropes are characterized by a high preservation of relict endogenous surfaces. The diamond has the appearance of a flattened aggregate with the distinct octahedron faces modified by surfaces of joint growth with other mineral grains. Findings of diamonds and signs of the formation of the diamond indicator minerals in the stream sediments of the studied area make it possible to detect their nearby original sources.

Very few zircon-bearing, kimberlite-hosted mantle eclogite xenoliths have been identified to date; however, the zircon they contain is crucial for our understanding of subcratonic lithospheric mantle evolution and eclogite genesis. In this study, we constrain the characteristics of zircon from mantle eclogite xenoliths based on existing mineralogical and geochemical data from zircons from different geological settings, and on the inferred origin of mantle eclogites. Given the likely origin and subsequent evolution of mantle eclogites, we infer that the xenoliths can contain zircons with magmatic, metamorphic and xenogenic (i.e. kimberlitic zircon) origins. Magmatic zircon can be inherited from low-pressure mafic oceanic crust precursors, or might form during direct crystallization of eclogites from primary mantle-derived melts at mantle pressures. Metamorphic zircon within mantle eclogites has a number of possible origins, ranging from low-pressure hydrothermal alteration of oceanic crustal protoliths to metasomatism related to kimberlite magmatism. This study outlines a possible approach for the identification of inherited magmatic zircon within subduction-related mantle eclogites as well as xenogenic kimberlitic zircon within all types of mantle eclogites. We demonstrate this approach using zircon grains from kimberlite-hosted eclogite xenoliths from the Kasai Craton, which reveals that most, if not all, of these zircons were most likely incorporated as a result of laboratory-based contamination.

New mineralogical and isotope–geochemical data for zircon megacrysts (n = 48) from alluvium of Kholomolokh Creek (a tributary of the Ebelakh River) are reported. Using the geochemical classification schemes, the presence of zircons of kimberlitic and carbonatitic genesis was shown. The U–Pb dating of zircons revealed two major age populations: the Triassic (258–221 Ma, n = 18) and Jurassic (192–154 Ma, n = 30). Weighted mean 206Pb/238U ages allowed us to distinguish the following age stages: 155 ± 3, 161 ± 2, 177 ± 1.5, 183 ± 1.5, 190 ± 2, 233 ± 2.5, and 252 ± 4 Ma. It is suggested that the Ebelyakh diamonds could have been transported from the mantle depths by kimberlite, as well as by other related rocks, such as carbonatite, lamprophyre, lamproite, olivine melilitite, etc. Diamonds from the Ebelyakh placers most likely have polygenic native sources and may be associated with polychronous and multistage Middle Paleozoic and Mesozoic kimberlite and alkaline–ultrabasic magmatism in the eastern slope of the Anabar Shield (the Ebelyakh, Mayat, and Billyakh river basins).

Diamonds were lately identified in chromitites from ophiolites and in volcanic rocks. Although the tectonic settings of diamonds found in these rocks are different, the diamonds are identical in small size, cuboctahedral habit, sets of minor admixture elements, and isotopic characteristics. A model is suggested for their formation during various stages of a single evolutionary cycle of the oceanic lithosphere, in relation to the geochemical and dynamic features of an ascending flow of mantle material, which produces the oceanic lithosphere at mid-oceanic ridges. In contrast to the continental lithosphere, in which mantle diamonds are usually related to kimberlite and lamproite magmatism in the presence of abundant CO2-rich fluid, diamonds in the oceanic lithosphere crystallize in environments poor in fluid and containing carbon mostly in its reduced forms. In the asthenospheric part of the ascending flow, carbon may occur in the form of nanometer-sized diamonds. In the upper parts of the oceanic lithosphere, the diamonds are overgrown and become microdiamonds (0.2–0.7 mm) within chromitites. After basaltic magma is derived from pyrolite, the residual harzburgites with lenses of diamondiferous chromitites are brought (at spreading) to the convergent boundaries of oceanic lithospheric plates, where the following two processes can proceed. If the oceanic lithosphere collides with a continental plate, the obducted material of the oceanic lithosphere is transferred to the surface of the continental margin and forms ophiolite massifs hosting diamond-bearing chromitites. If the oceanic lithosphere is subducted, the residual peridotite already enriched in volatiles is remelted. The arc magmas thus derived host diamond microcrystals, which have been formed in the chromitites and are sometimes found in volcanic lavas and ashes.

Basing on generalization of large actual material on complex investigation of diamond its characteristic in Upper Paleozoic and Mesozoic sedimentary thick layers of the Siberian platform is provided. Special attention is paid to the Central-Siberian sub-province, where it is convincingly shown that the area of development of individual diamond macro-associations is limited by a specific diamondiferous region, within which complexes of different in age terrigenous and coastal Upper Paleozoic and Mesozoic sediments are developed. Identified in some diamondiferous regions proximity of typomorphic features of diamonds in sedimentary thick layers of these ages testifies about formation of these collectors due to washout of more ancient productive layers or Middle Paleozoic primary sources. Polygeny of mineralogical associations of diamonds from different in age placers within some diamondiferous regions was noted, which may be successfully used when forecasting and prospecting primary sources of the mineral. Diamond and its tipomorphic features are one of the main criteria for forecasting and searching for root sources Materials on heterogeneity of the Viljujsko-Marhinska zone of deep faults with respect to productive kimberlite magmatism, which is associated with areals of the hard consolidated basement of the Archean age (Botuobinskij and Tjungskij cratons) obtained in the framework of medium scale forecast and search studies of typomophic features of diamonds have an important practical conclusion. The results of a study of the typomorphic features of diamonds from the most well-studied kimberlite bodies indicatle heterogeneities in the structure of the upper mantle even within the Central Siberian diamondiferous subprovince, especially with respect to the distributionof focirly rare coloured crystals (II, III and IV varieties) presumably of ecbgite genesis, associated with deep diamandiferous xenoliths of various composition. These varieties of diamonds are rare and accessory in kimberlite bodies, however their findings in rashes even in a single amount, can serve as a basis for localizing the territory of the search for indigenous sources. The analysis of typomorphic features of diamonds indicates the high prospectivity of placer oceurrences of the Central Siberian diamondiferous pronnce for the discovety of new highly productive kimberlite pipes.

Whether hydrogen incorporated in nominally anhydrous mantle minerals plays a role in the strength and longevity of the thick cratonic lithosphere is a matter of debate. In particular, the percolation of hydrogen-bearing melts and fluids could potentially add hydrogen to the mantle lithosphere, weaken its olivines (the dominant mineral in mantle peridotite), and cause delamination of the lithosphere's base. The influence of metasomatism on hydrogen contents of cratonic mantle minerals can be tested in mantle xenoliths from the Slave Craton (Canada) because they show extensive evidence for metasomatism of a layered cratonic mantle. Minerals from mantle xenoliths from the Diavik mine in the Lac de Gras kimberlite area located at the center of the Archean Slave craton were analyzed by FTIR for hydrogen contents. The 18 peridotites, two pyroxenites, one websterite and one wehrlite span an equilibration pressure range from 3.1 to 6.6 GPa and include samples from the shallow (≤145 km), oxidized ultra-depleted layer; the deeper (∼145–180 km), reduced less depleted layer; and an ultra-deep (≥180 km) layer near the base of the lithosphere. Olivine, orthopyroxene, clinopyroxene and garnet from peridotites contain 30–145, 110–225, 105–285, 2–105 ppm H2O, respectively. Within each deep and ultra-deep layer, correlations of hydrogen contents in minerals and tracers of metasomatism (for example light over heavy rare-earth-element ratio (LREE/HREE), high-field-strength-element (HFSE) content with equilibration pressure) can be explained by a chromatographic process occurring during the percolation of kimberlite-like melts through garnet peridotite. The hydrogen content of peridotite minerals is controlled by the compositions of the evolving melt and of the minerals and by mineral/melt partition coefficients. At the beginning of the process, clinopyroxene scavenges most of the hydrogen and garnet most of the HFSE. As the melt evolves and becomes enriched in hydrogen and LREE, olivine and garnet start to incorporate hydrogen and pyroxenes become enriched in LREE. The hydrogen content of peridotite increases with decreasing depth, overall (e.g., from 75 to 138 ppm H2O in the deep peridotites). Effective viscosity calculated using olivine hydrogen content for the deepest xenoliths near the lithosphere-asthenosphere boundary overlaps with estimates of asthenospheric viscosities. These xenoliths cannot be representative of the overall cratonic root because the lack of viscosity contrast would have caused basal erosion of lithosphere. Instead, metasomatism must be confined in narrow zones channeling kimberlite melts through the lithosphere and from where xenoliths are preferentially sampled. Such localized metasomatism by hydrogen-bearing melts therefore does not necessarily result in delamination of the cratonic root.

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 results of U–Pb isotope dating of perovskites from silicate–calcite vein rocks spatially associated with the Kusa–Kopan gabbro intrusion are presented. At present, the genesis of these silicate–carbonate rocks remains controversial. The obtained U–Pb ages are 497.0 ± 4 Ma for perovskite from the Perovskite mines and 468 ± 6.4 Ma for that from the Zelentsovskaya mine. The obtained ages are significantly different from the age of the Kusa–Kopan gabbro intrusion (1379 ± 8 Ma). Furthermore, the REE distribution trend (LA–ICP–MS) in the perovskites studied is similar to that in perovskites from carbonatites and kimberlites. Together with the geochronological data, this suggests that the carbonate–silicate rocks studied originated from a carbonatite origin. Additional confirmation of the manifestation of Early Paleozoic diastrophism in the region studied is the U–Pb age of zircons from volcanics of the Bashkir anticlinorium obtained earlier by various methods.

Introduction: The results of a comprehensive study of the geological structure and material composition of the weathering crust of the kimberlites in north-east Angola are presented. An important applied problem is the assessment of the degree of enrichment of the weathering crust by deep minerals for forecasting and searching for new diamond deposits of both primary and placer types. Methodology: The Catoca kimberlite pipe, characterized not only by an insignificant erosional section and preservation of the crater structure, but also by a wide petrographic spectrum of rocks and their intense post-magmatic and hypergenic variation, was chosen as a reference object. The collection of ore samples and flow samples from the upper horizons of the Catoca pipe and a number of other bodies of this field, as well as rocks containing kimberlites, were collected for the study of the geological structure and material composition of weathering crusts of weakly eroded Angola kimberlite pipes. Results and discussion: Two genetic types of rocks were distinguished in the Catoca kimberlite pipe: kim- berlites with their derivatives and a complex of volcanic-sedimentary formations filling the upper parts of the crater of diatreme. In general, the profile of the weathering crust is divided into two parts: lower and upper. The lower part (disintegration zone) is represented by slightly altered autolithic kimberlite breccias, fractured and partially ocherized. The upper, the most hypergene-altered zone, in turn, is divided into carbonate and non-carbonate parts. Conclusions: Two processes of changes in the kimberlite rocks of the region were revealed. The first process is the phased conversion of olivine to high-temperature, then low-temperature serpentine. The second process is the degradation of serpentine with the simultaneous emergence of a series of swellable minerals, starting with saponite through a series of intermediate metastable mixed-layer formations, out of which the ordered variety of lyzardite-saponite, identified for the first time, was relatively more stable compared to other ordered mixed-layer phases of the trioctahedral type. This finding emphasizes the specific conditions of crust formation of the weathering kimberlites of the African region.

Pyroclastic deposits of the Holocene Igwisi Hills kimberlite volcanoes, Tanzania, preserve unequivocal evidence for rapid, syn-eruptive agglutination. The unusual pyroclasts are composed of ash-sized particles agglutinated to each other by thin necks. The textures suggest the magma was disrupted into droplets during ascent. Collisions between particles occurred within a volcanic plume and on deposition within the conduit to form a weakly agglutinated, porous pyroclastic deposit. Theoretical considerations indicate that agglutination occurred over short timescales. Agglutinated clasts were entrained into weak volcanic plumes and deposited around the craters. Our results support the notion that agglutination can occur during kimberlite eruptions, and that some coherent, dense rocks in ancient kimberlite pipes interpreted as intrusive rocks could instead represent agglutinated pyroclastic rocks. Differentiating between agglutinated pyroclastic rocks and effusive or intrusive rocks in kimberlite pipes is important because of the potential effects that pyroclastic processes might have on diamond concentrations in deposits.

Major, minor and trace element compositions of mantle xenocrysts from Devonian kimberlite pipes in the Priazovie give an insight into the mantle structure beneath the SE Ukranian Shield and its evo...

The present study attempts a conjugate analysis of satellite-based remote sensing, gravity, and magnetic data for evaluation of structures and tectonic for new insights on Kimberlite emplacement ar...

Xenoliths and xenocrysts of mantle material from kimberlite dikes located underground at the Certac Au mine, Québec, in the eastern Superior Craton, were studied in terms of the major element composition of their constituent minerals. The kimberlite was dated at 1151 ± 46 Ma by the U-Pb perovskite method. This suite thus provides a rare glimpse into the Mesoproterozoic mantle of the Superior Craton. Two parageneses of mantle material unrelated to the kimberlite magmatism occur: (1) an olivine + ilmenite ± magnetite association characterized by relatively Fe-rich olivine (Mg# = 0.68–0.84) and ilmenite enriched in Mg and Cr (4–13 wt.% MgO, Cr2O3 up to 3 wt.%), and (2) spinel peridotite characterized by Mg-rich olivine (Mg# = 0.91–0.94). The Fe-rich association is interpreted as a magmatic cumulate likely unrelated to the kimberlite. No mantle-derived garnet occurs in the xenoliths or as xenocrysts. The presence of Cr-rich spinel (Cr# = 0.84–0.98) in high temperature (860–953 °C) chromite peridotite indicates bulk compositions too depleted in Al for garnet to be stable, although geothermometry suggests they equilibrated at depths corresponding to garnet stability (90–131 km, depending on the geothermal gradient). Alternatively, the presence of phlogopite in two of the three high temperature (i.e., deepest) chromite peridotites suggests the absence of garnet and presence of low-Al chromite may have been caused by metasomatism from a K-rich fluid that replaced garnet with phlogopite + clinopyroxene ± chromite. Less depletion at shallower depths is indicated by a chromite (Cr# = 0.60) dunite that equilibrated at 831 °C and a low temperature (752 °C) Mg-Al-spinel lherzolite.

Mantle xenoliths were found in alkaline basalts of Tokinsky Stanovik (TSt) in the Dzhugdzhur-Stanovoy superterrane (DS) and Vitim plateau (VP) in the Barguzin–Vitim superterrane (BV) (Stanovoy suture area) at junction of the Central Asian Orogenic Belt (CAOB) and the Siberian craton (SC). Xenoliths from TSt basalts are represented by spinel lherzolites, harzburgites, wehrlites; while VP basalts frequently contain spinel–garnet and garnet peridotites lherzolites, and pyroxenites. Xenoliths in kimberlites of the Siberian craton are mainly represented by garnet-bearing lherzolites with abundant eclogite xenoliths (age of 2.7–3.1 Ga), which were not found in mantle of superterranes. The Re-Os determinations point to the Early Archean age of peridotites and eclogites from mantle beneath the Siberian craton. The major and trace (rare-earth and high-filed strength) elements and Nd-Sr-Os composition were analyzed in the peridotites (predominant rocks) of lithospheric mantle at junction of the Central Asian Orogenic Belt and Siberian Craton. The degree of rock depletion in CaO and Al2O3 and enrichment in MgO relative to the primitive mantle in the peridotites of the Dzhugdzhur–Stanovoy superterrane is close to that of the Siberian craton. The peridotites of the Barguzin–Vitim superterrane are characterized by much lower degree of depletion and have mainly a primitive composition. Mantle melting degree reaches up to 45–50% in the Siberian Craton and Dzhugdzhur-Stanovoy superterrane, and is less than 25% in the Barguzin–Vitim terrane. The mantle peridotites of the craton as compared to those of adjacent superterranes are enriched in Ba, Rb, Th, Nb, and Ta and depleted in Y and REE from Sm to Lu. However, all studied peridotites are characterized by mainly superchondritic values of Nb/Ta (>17.4), Zr/Hf (>36.1), Nb/Y (>0.158), and Zr/Y (>2.474). The Nb/Y ratio is predominantly >1.0 in SC peridotites and 0.115 but usually lower than 0.1296 (primitive upper mantle value) in the peridotites of the Dzhugdzhur–Stanovoy and Barguzin–Vitim superterranes. Thus, the geochemical and isotopic composition of peridotites indicates different compositions and types of mantle beneath the Siberian craton and adjacent superterranes of the Central Asian Orogenic Belt in the Early Archean, prior to the formation of 2.7–3.1 Ga eclogites in the cratonic mantle.

How cratons, the ancient cores of continents, evolved since their formation over 2.5 Ga ago is debated. Seismic tomography can map the thick lithosphere of cratons, but its resolution is low in sparsely sampled continents. Here we show, using waveform tomography with a large, newly available dataset, that cratonic lithosphere beneath Africa is more complex and fragmented than seen previously. Most known diamondiferous kimberlites, indicative of thick lithosphere at the time of eruption, are where the lithosphere is thin today, implying surprisingly widespread lithospheric erosion over the last 200 Ma. Large igneous provinces, attributed to deep-mantle plumes, were emplaced near all lithosphere-loss locations, concurrently with or preceding the loss. This suggests that the cratonic roots foundered once modified by mantle plumes. Our results imply that the total volume of cratonic lithosphere has decreased since its Archean formation, with the fate of each craton depending on its movements relative to plumes., Cratons represent the ancient cores of continental plates and are generally thought to have been stable since the Archean. Here however, the authors combine seismic analysis with kimberlite data to infer complete destruction of cratonic lithosphere in some places of the African continent.

Identifying the composition of primary/primitive mantle melts is crucial for understanding the mantle's evolution and mantle-derived magmatism. Melt inclusions in mantle xenoliths provide key information about such melts. This study used confocal Raman spectroscopy to characterize mineral assemblage of unexposed crystallized secondary melt inclusions in the olivine from the xenoliths of the sheared garnet peridotites from the Bultfontein kimberlite pipe (Kimberley cluster, Kaapvaal Craton, South Africa). The studied peridotites originated from 112- to 146-km mantle depths. In total, 16 minerals were identified among daughter crysatls, which include carbonates (calcite, magnesite, dolomite), alkali carbonates (eitelite, nyerereite, gregoryite/natrite, K–Na–Ca–carbonate (K,Na)2Ca(CO3)2 (K analogue of nyerereite), alkali carbonates with additional anions (northupite, bradleyite, burkeite), alkali sulfates (glauberite, thenardite, aphthitalite), apatite, tetraferriphlogopite, and magnetite. Several more daughter minerals gave distinct Raman spectra, but they were not determined due to the lack of similar spectra in the databases. Carbonates are predominant among the daughter minerals in the melt inclusions. Many daughter minerals are rich in alkalis. These facts indicate that melt(s), parental for the inclusions, is alkali-rich carbonate in composition. Two possible models were suggested for the origin of these melt inclusions: (1) in situ fracturing of olivine and the mantle melt infiltration shortly before the sheared peridotites were entrained by the ascending kimberlitic magma; (2) infiltration of the transporting kimberlite melt into xenoliths during ascent. Both models imply that the alkali-rich carbonate melt(s) that interacted with peridotites originated at a greater depth than the entrapment level of studied xenoliths (>150 km), that is, at the base of the lithosphere or in the asthenosphere. This melt is genetically related to the kimberlite magmatism that formed the Bultfontein pipe and points at the alkali-rich carbonate composition of primary kimberlite melt.

Several individual particle native golds were observed in two Mesozoic Group II kimberlites dikes in the southeastern margin of North China Craton (NCC). This discovery provides new information of the nature of the Mesozoic lithospheric mantle beneath the southeastern NCC, the metallogenic setting of gold deposits in the Jiaodong peninsula and the metallogenic theory of decratonic gold deposits.

The results of a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb dating and a Hf isotope study of zircon crystals separated from small eclogite xenoliths found in Devonian kimberlites within the Prypyat horst, Ukraine, have been reported. The studied area is located in the junction zone between the Sarmatian and Fennoscandian segments of the East European Platform. Four laser ablation sites on two zircon grains yielded Paleoproterozoic U–Pb ages between 1954 ± 24 and 1735 ± 54 Ma. In contrast, three of four Hf sites revealed negative εHf values and Paleoarchean to Mesoarchean model ages, excluding the possibility that the eclogite xenoliths represented segments of a juvenile Paleoproterozoic subducted slab or younger mafic melts crystallized in the subcontinental lithospheric mantle. A single laser ablation Hf spot yielded a positive εHf value (+3) and a Paleoproterozoic model age. Two models for eclogite origin can be proposed. The first foresees the extension of the Archean lower-crustal or lithospheric roots beneath the Sarmatia–Fennoscandia junction zone for over 200 km from the nearest known outcrop of Archean rocks in the Ukrainian Shield. The second model is that the Central Belarus Suture Zone represents a rifted-out fragment of the Kola–Karelian craton that was accreted to Sarmatia before the actual collision of these two segments of Baltica.

Most of the diamond deposits in China are in the North China Craton. In addition to gem diamonds in kimberlite, a large number of microdiamonds have also been discovered in alkaline dolerites. These microdiamonds show very different characteristics from those recovered in kimberlite. Here, we report the morphology, colour, nitrogen contents, and carbon isotopic compositions of the diamonds recovered from the alkalic dolerites in eastern China. The microdiamonds are mainly cube and rhombic dodecahedron with diameters of 0.2 to 0.6 mm. Infrared spectrum analysis shows that these microdiamonds are mostly type Ib with a small amount of type Ia. The Y centre is obvious in type Ib diamond. Modelling mantle residence times for the IaAB diamonds is about 550 Ma. Nitrogen contents of the diamonds range from 4.5–503 ppm, with a median value of 173 ppm. The total δ13C range of the microdiamonds varies between −18.6 and −21.1‰ and are similar to those of ophiolite diamond.

Multiple sulphur isotopic compositions of sulphides from Kaapvaal craton mantle eclogites allow to elucidate the recycling of sulphur into the deep Earth and to differentiate between recycled crust and mantle origins of eclogite-hosted sulphides, including the precious metals that they capture. We present multiple sulphur isotope ratio measurements by secondary ion mass spectrometry for sulphides from a collection of mantle-derived eclogite xenoliths from Proterozoic and Mesozoic kimberlite occurrences in South Africa (Premier, Roberts Victor, Jagersfontein). Previous work established that the host eclogites have elemental and oxygen isotopic compositions in support of seawater-altered oceanic lithosphere protoliths, and for many of these xenolith suites Archean ages have been suggested. The eclogite-hosted sulphides have δ 34 S values from −5.7 to + 29 ‰ , with the upper end of this wide range representing the highest-ever recorded δ 34 S composition of material derived from the Earth's mantle. The Δ 33 S values range from −0.29 to + 0.18 ‰ and do not record significant mass-independent sulphur isotope fractionation, i.e., there is no compelling S-MIF signature. Most of the sulphide grains have δ 34 S values that fall within a range between −6 and + 4 ‰ , and they probably retain an isotopic record of sulphides that formed originally within altered oceanic crust. In contrast, the highly positive δ 34 S values from +13 to + 29 ‰ detected in sulphide grains from a single eclogite xenolith are similar to those of marine sulphates, which were probably a minor sulphur component of the oceanic crustal protolith. The lack of a significant S-MIF signature in the eclogitic sulphides that show δ 34 S evidence for a recycled crust origin implies that this sulphur component stems from a 2.4 Ga post-Archean surficial reservoir. This finding suggests that the cratonic mantle eclogites may have formed from post-Archean oceanic crust (e.g., Paleoproterozoic eclogite protoliths), or – as is preferred here – the ‘surficial’ sulphur was introduced into the cratonic root during relatively young metasomatic events and is thus unrelated to eclogite petrogenesis and Archean continent formation.

Camp dels Ninots is a mixed hard-soft maar-diatreme located in the Catalan Volcanic Zone (NE of Iberia), in which intra-maar lake sediments have preserved one of the most remarkable Pliocene fossil records in Europe. Geophysical surveys combined with the geological map and 11 boreholes, including two new continuous intra-crater drill cores, have enabled the construction of a 3D geological model of this maar-diatreme and its basement. The formation of this maar-diatreme started with a vent-opening phreatomagmatic explosion at the intersection between a regional fault and the Paleozoic groundwater level at a depth of 210 m. We infer and calculate the geometry, dip direction and dip angle of this regional fault. During the eruption, mixed Strombolian and phreatomagmatic episodes occurred, forming the tuff ring and filling the diatreme with minimum estimated volumes of 0.012 and 0.004 km3, respectively. The diatreme infill is composed of three main lithofacies that include tuff-breccias, welded scoriae, and mafic intrusions into the phreatomagmatic breccias. Thus, the stratigraphy of the diatreme succession suggests a progression of explosive events from deeper to shallower zones with short lateral migration of explosion vents, which control its final morphology, without evidence for significant deep enlargement of the diatreme during the later phases. This generated a wide funnel-shaped with low diatreme wall angles that differs from kimberlite pipes with great depths and sharp slope geometries. Hence, such 3D geological model helps to understand the complex architecture of maar-diatreme structures, highlighting the lack of geological modeling of this type of monogenetic system., We would like to thank the landowners, especially Mr. Jaume (Met), for their permission and help to work in the area, and the Town Council of Caldes de Malavella. We also would like to the Departament de Cultura of the Generalitat de Catalunya for the economic funding of the drill coring campaign under the project CLT009/18/00052. This study was partially funded by the project of the Spanish Government and the SGR2017-859 and SGR-2017-1666 projects of the Generalitat de Catalunya. X. Bolós was funded by a UNAM-DGAPA postdoctoral fellowship (2016–2018). O. Oms is part of SGR-2017-1666 Research Group of the Generalitat de Catalunya. B. Gómez de Soler and G. Campeny are funded by the CERCA Programme/Generalitat de Catalunya. The Institut Català de Paleoecologia Humana i Evolució Social (IPHES-CERCA) has received financial support from the Spanish Ministry of Science and Innovation through the ‘María de Maeztu’ program for Units of Excellence (CEX2019-000945-M).

Monomineralic millimeter-sized olivine nodules are common in kimberlites worldwide. It is generally thought that such ‘dunitic nodules’ originate from the base of the cratonic lithosphere and that their formation marks the onset of deep-rooted kimberlite magmatic plumbing systems. However, thermobarometric constraints to support such a model have been lacking thus far. This study focuses on the petrography and textures, as well as on pressure–temperature estimations, of well-preserved dunitic nodules from the Quaternary Igwisi Hills kimberlite lavas on the Tanzania craton, with the ultimate goal to constrain their origins. We utilize EBSD-determined textural information in combination with olivine geochemistry data determined by EPMA and LA-ICP-MS methods. We find that host olivine grains in these nodules are compositionally similar to olivine in garnet-facies cratonic mantle peridotites, and such an association is supported by garnet inclusions within olivine. Projection of Al-in-olivine temperatures onto a regional geotherm suggests that the host olivine grains equilibrated at ~ 100–145 km depth, which points to origins from mid-lithospheric levels down to the lower cratonic mantle if a depth of 160–180 km is considered for the lithosphere–asthenosphere transition beneath the Tanzania craton. These first pressure–temperature estimates for dunitic nodules in kimberlites suggest that their formation also occurs at much shallower depths than previously assumed. Recrystallized olivine grains (i.e., neoblasts) show random crystallographic orientations and are enriched in minor and trace elements (e.g., Ca, Al, Zn, Sc, V) compared to the host olivine grains. These features link neoblast formation to melt-assisted recrystallization of cratonic mantle peridotite, a process that persisted during kimberlite magma ascent through the lower half of thick continental lithosphere. Partial recrystallization of olivine-rich mantle xenoliths makes these materials texturally weaker and subsequent liberation of mineral grains promotes the assimilation of compositionally ‘unstable’ orthopyroxene in rising carbonate-rich melts, which is considered to be an important process in the evolution of kimberlite magmas. Dunitic nodules in kimberlites and related rocks may form as melt–rock equilibration zones along magmatic conduits within the lower half of the cratonic mantle column all the way up to mid-lithospheric depth. Such an origin potentially links dunitic nodules to olivine megacrysts, which are equally considered as melt/fluid-assisted recrystallization products of peridotitic mantle lithosphere along the ascent pathways of deep-sourced CO2–H2O-rich ultramafic melts.

Maar-diatreme volcanoes are the second-most common type on land, occurring in volcanic fields within all major tectonic environments. Their deposits typically contain an abundance of lithic fragments quarried from the substrate, and many contain large, deep-sourced lithic fragments that were erupted to the surface. Primary volcaniclastic deposits fill the diatreme structure formed during eruption. There is negligible inelastic deformation of diatreme-adjacent country rock, indicating that country rock is removed to create the diatreme structures, either by being shifting downward below observable levels, ejected upward to contribute to surficial deposits, or dissolved and hidden in magma erupted or intruded at depth. No previous study has systematically reviewed and analysed the reported lithic fragments of maar-diatreme systems. We present a comprehensive compilation from published work of lithic characteristics in maar ejecta rims and in diatreme deposits of both common and kimberlite maar-diatremes. For maar-diatremes and their tephra ring deposits, we find no correlations among lithic clast sizes, shapes, depositional sites, and excavation depths. This is difficult to reconcile with models involving systematic diatreme deepening coupled with tephra-ring growth, but consistent with those involving chaotic explosions and mixing. Larger amounts of data are needed to further examine how these types of volcanoes operate.

The Sm–Nd isotope systematics and geochemistry of eclogitic, websteritic and peridotitic garnet and clinopyroxene inclusions together with characteristics of their corresponding diamond hosts are presented for the Letlhakane mine, Botswana. These data are supplemented with new inclusion data from the nearby (20–30 km) Orapa and Damtshaa mines to evaluate the nature and scale of diamond-forming processes beneath the NW part of the Kalahari Craton and to provide insight into the evolution of the deep carbon cycle. The Sm–Nd isotope compositions of the diamond inclusions indicate five well-defined, discrete eclogitic and websteritic diamond-forming events in the Orapa kimberlite cluster at 220 ± 80 Ma, 746 ± 100 Ma, 1110 ± 64 Ma, 1698 ± 280 Ma and 2341 ± 21 Ma. In addition, two poorly constrained events suggest ancient eclogitic (> 2700 Ma) and recent eclogitic and websteritic diamond formation (TCHUR) between 2.86 and 3.38 Ga, the diamonds studied here span almost the entire temporal evolution of the SCLM of the Kalahari Craton. The new data demonstrate, for the first time, that diamond formation occurs simultaneously and episodically in different parageneses, reflecting metasomatism of the compositionally heterogeneous SCLM beneath the area (~ 200 km2). Diamond formation can be directly related to major tectono-magmatic events that impacted the Kalahari Craton such as crustal accretion, continental breakup and large igneous provinces. Compositions of dated inclusions, in combination with marked variations in the carbon and nitrogen isotope compositions of the host diamonds, record mixing arrays between a minimum of three components (A: peridotitic mantle; B: eclogites dominated by mafic material; C: eclogites that include recycled sedimentary material). Diamond formation appears dominated by local fluid–rock interactions involving different protoliths in the SCLM. Redistribution of carbon during fluid–rock interactions generally masks any potential temporal changes of the deep carbon cycle.

The main purpose of the article — is using the complex of structural-tectonic, geological-geophysical and lithologic-structural investigations, to describe in general the brecciated formations and pipe-like bodies of their localization as a precondition for solving the diamond-bearing problems of the Raihorodska suite (Paleocene) by the example of the Hruzske field of explosive structures in the central part of the Ukrainian Shield. Structural-tectonic, geophysical and morphostructural analyzes of the Precambrian basement surface have been used for diagnostics and outlining of local isometric pipe structures. Petrographic composition of the Hruzske field rocks was studied in core samples from wells No. 4087 (structure Hruzka-Pivdenna), 4040, 4043 and 4045 (structure Lisova-Skhidna), drilled by GPE-37 SE «Kirovheolohiia». Lithologic-stratigraphic and micropaleontological methods were used to determine the age of brecciated rocks. The morphology of bodies, some specific petrographic peculiarities of brecciated rocks of the Hruzske field are characterized by the complex of lithologic-structural features, as well as conclusions regarding their belonging to the endogenous (magmatogenic) group of diamond-bearing formations are made. Brecciated rocks of the Raihorodska suite are attributed to the clay-fine-clastic breccias, which are clearly confined to the lows in the Precambrian basement of the Shield central part and fill the depressions like the diatremes. Their explosive nature is substantiated; the Cretaceous-Palaeogene age of formation is confirmed; the rocks are compared with «sandy» tuffs of the Argyle lamproite pipe in Western Australia and volcanoclastic kimberlites of the Fort a la Corne area in Canada. It has been shown for the first time that the depressions in the Precambrian basement of the Ukrainian Shield central part are pipe-shaped bodies of the stockwork-maars type with a clearly expressed non-eroded craterous part. At a depth, they pass into the system of un-oriented joints, which played the role of incurrent canals for a mobile alkaline-ultrabasic magma, rich in volatile components. According to the structural-material characteristics, these specific brecciated formations of the Raihorodska suite are attributed to the products of rapid brecciation during the fluidizate-explosive processes of the maar volcanism development. Based on the performed researches it is possible to estimate the prospects of pipe-like bodies in relation to the search for industrial diamonds deposits on the Shield, to distinguish local structures, perspective on manifestations of explosive processes and related endogenous (kimberlite-lamproite) diamond content.

The Nyurbinskaya and Botuobinskaya kimberlitic pipes were in the focus of a comprehensive study aimed to investigate their structural and material positions as the main deposits in the Nakyn field (Yakutian Diamondife‐ rous Province, Russia). This paper present the study results and 3D structural‐material models showing the formation of these deposits. In application to geological studies, the 3D modeling technologies allow taking into account the ani‐ sotropy of material complexes comprising kimberlite pipes, as well as inconsistencies in the structural and morpho‐ logical properties of ore‐bearing structures. In order to discover the structural positions and features of the fault‐ block structures of the deposits, tectonophysical methods were used in combination with tacheometric surveys. Based on this more comprehensive and integrated approach, the existing fault patterns were clarified in detail; elements of the internal fault structure were mapped; fault azimuths and dip angles were estimated; and thickness values were obtained. Computer processed data were used to construct 3D models showing the fault‐block structures of the Nyurbinskaya and Botuobinskaya pipes. The mineralogical, petrographic and diamond‐bearing features of various kimberlite generations comprising these pipes were investigated in order to reconstruct the morphology and spatial positions of each of the selected complexes in the current cross‐section and in accordance with intrusion phases. The 3D frame models of geological bodies were constructed for all the magmatic phases, including porphyry kimberlite and eruptive and autolithic kimberlite breccia. The structural‐material models for the Nyurbinskaya and Botuobin‐ skaya pipes were based on a synthesis of their material and structural features discovered in the previous stages of the study. The models presented in this paper are used to discuss temporal relationships between faults in the kim‐ berlitic structure and material complexes comprising the pipes. The models show that the pipes occurred in the near‐ surface structures of shear tension, which developed in the areas where the NNE‐striking fault was conjugated with the ENE‐ and NE‐striking faults in the fault zone resulting from several stage of the tectono‐magmatic activity. In this case, the kimberlite melt material was transported in discrete portions from the source through deep‐seated faults, and the faults acted as channels characterized by an increased permeability. Disjunctive elements identified in this study facilitated magma movements and localization of kimberlite bodies.

Kimberlites are rare, enigmatic, low-volume igneous rocks. They are highly enriched in magnesium, volatiles (CO2 and H2O) and incompatible trace elements and are thought to be the most deeply derived (>150 km) magmatic rocks on Earth. Kimberlites occur in ancient and thick continental lithosphere, forming intrusive sheets and composite pipes, commonly in clusters. Despite their rarity, kimberlites have attracted considerable attention because they entrain not only abundant mantle fragments but also diamonds, which can provide a uniquely rich picture of the deep Earth. This issue summarises current thinking on kimberlite petrology, geochemistry, and volcanology and outlines the outstanding questions on the genesis of kimberlites and associated diamond mines.

Magnetoplumbite-group minerals from various paragenetic assemblages, including a xenolith of altered garnet lherzolite from the Obnazhennaya kimberlite pipe in Yakutia, sulfide-free metasomatic Pb–Zn–Sb ore from the Pelagonian massif in the Republic of North Macedonia, and some other metasomatic occurrences have been studied with electron microprobe, as well as using IR and Raman spectroscopy. New data on isomorphic substitutions and crystal chemistry of the magnetoplumbite-group minerals have been obtained. Three potentially new mineral species belonging to this group have been identified: Al-dominant analogue of yimengite, Ba-dominant analogue of nežilovite, and Mn-dominant analogue of plumboferrite.

The paper is dedicated to the study of the Devonian magmatic association of the Eastern Azov region, which is a part of the Pripyat-Dnieper-Donets rift zone. The association includes gabbros, peridotites, pyroxenites, and lamprophyre dikes of the Pokrovo-Kireevsky massif (PKM) and picrites, picrobasalts, and basalts of the Anton-Taram Formation (ATF). Analysis of clinopyroxenes of different generations from the PKM micaceous gabbro and the ATF alkaline picrite provided insight into the mantle source of these rocks and the evolution of melts, which determined the close spatiotemporal association of kimberlites, basites, ultramafic rocks, including alkaline varieties. Clinopyroxenes from the micaceous gabbro are composed of Cpx1 (Mg # = 0.87–0.88) or Сpx2 (Mg # = 0.80–0.81) cores and Cpx3 external zones (Mg # = 0.70–0.76). Clinopyroxenes from alkaline picrite are composed of Сpx2 cores (Mg # = 0.80–0.84) and external Cpx3 zones (Mg # = 0.71–0.78). Clinopyroxenes in general have an upward concave multielement pattern, with enrichment in LREE, depletion in Ba, Nb, and HREE, Zr–Hf negative anomaly, and, additionally, negative Sr-anomaly in Cpx2 and Cpx3. The calculated equilibrium melts for Сpx2 from the micaceous gabbro are very close in composition to this gabbro, and those for Cpx2 from the alkaline picrite coincide in composition with this picrite, and in general are close to ATF picritic lavas. The high Mg# and Cr content in cores Cpx1 indicate that this mineral was derived from the earliest weakly differentiated magma close to the primary melt. The presence of a negative Zr–Hf anomaly in Cpx1 geochemical patterns at ZrPM 0.8) melts, which generated picrobasalts and lamprophyres. The geochemical similarity of the early Cpx1 cores with clinopyroxenes from ilmenite-bearing mantle metasomatites is consistent with the assumption that ultrahigh-Ti primary melts of the Eastern Azov lamprophyres were derived from carbonated ilmenite-bearing, and likely, phlogopite-bearing (PIC) peridotites.

We studied the petrography, mineralogy, thermobarometry and whole-rock chemistry of 120 peridotite and pyroxenite xenoliths collected from the 156–138 Ma Chidliak kimberlite province (Southern Baffin Island). Xenoliths from pipes CH-1, -6, -7 and -44 are divided into two garnet-bearing series, dunites–harzburgites–lherzolites and wehrlites–olivine pyroxenites. Both series show widely varying textures, from coarse to sheared, and textures of late formation of garnet and clinopyroxene. Some samples from the lherzolite series may contain spinel, whereas wehrlites may contain ilmenite. In CH-6, rare coarse samples of the lherzolite and wehrlite series were derived from P = 2·8 to 5·6 GPa, whereas predominant sheared and coarse samples of the lherzolite series coexist at P = 5·6–7·5 GPa. Kimberlites CH-1, -7, -44 sample mainly the deeper mantle, at P = 5·0–7·5 GPa, represented by coarse and sheared lherzolite and wehrlite series. The bulk of the pressure–temperature arrays defines a thermal state compatible with 35–39 mW m–2 surface heat flow, but a significant thermal disequilibrium was evident in the large isobaric thermal scatter, especially at depth, and in the low thermal gradients uncharacteristic of conduction. The whole-rock Si and Mg contents of the Chidliak xenoliths and their mineral chemistry reflect initial high levels of melt depletion typical of cratonic mantle and subsequent refertilization in Ca and Al. Unlike the more orthopyroxene-rich mantle of many other cratons, the Chidliak mantle is rich (∼83 vol%) in forsteritic olivine. We assign this to silicate–carbonate metasomatism, which triggered wehrlitization of the mantle. The Chidliak mantle resembles the Greenlandic part of the North Atlantic Craton, suggesting the former contiguous nature of their lithosphere before subsequent rifting into separate continental fragments. Another, more recent type of mantle metasomatism, which affected the Chidliak mantle, is characterized by elevated Ti in pyroxenes and garnet typical of all rock types from CH-1, -7 and -44. These metasomatic samples are largely absent from the CH-6 xenolith suite. The Ti imprint is most intense in xenoliths derived from depths equivalent to 5·5–6·5 GPa where it is associated with higher strain, the presence of sheared samples of the lherzolite series and higher temperatures varying isobarically by up to 200 °C. The horizontal scale of the thermal-metasomatic imprint is more ambiguous and could be as regional as tens of kilometers or as local as

Monocrystalline type Ia diamonds with octahedral growth morphology prevail among lithospheric diamonds, including precious stones. Unlike less common ‘fibrous’ diamonds that grew from alkali-rich carbonate-bearing melts and fluids, the growth medium of ‘monocrystalline’ type Ia diamonds remains debatable. Here we report the first finding of an optically visible (~30 μm in size) carbonate inclusion in the center of a gem type Ia octahedral diamond from the Sytykanskaya kimberlite pipe, Yakutia. We found that the inclusion consists of submicron size carbonate phases represented by K 2 Ca(CO 3 ) 2 butschliite (~15 vol%), Na 2 Mg(CO 3 ) 2 eitelite (~5 vol%), and dolomite (~80 vol%). Although neither butschliite nor eitelite can coexist with dolomite under mantle P-T conditions, these phases readily appear all together in the quenched products of carbonatite melt under mantle pressures. Thus, at the moment of capture, the inclusion material was a carbonatite melt with the following composition 10(K 0.75 Na 0.25 ) 2 CO 3 ∙90(Ca 0.57 Mg 0.43 )CO 3 . The content of alkali carbonates at the level of 10 mol% indicates that the melt was formed at a temperature of ≥1300 °C. The high K/Na and Ca/(Ca + Mg) ratios in this melt indicate its derivation by partial melting of recycled marine sediments (pelites). Considering an age of the last subduction event beneath the Siberian craton, our new finding implies that subducting slabs drag carbonated material of the continental crust beneath ancient cratons, where it experiences partial melting to form a potassic dolomitic melt responsible for the formation of most diamonds, since the Late Archean.

The widely accepted paradigm of Earth's geochemical evolution states that the successive extraction of melts from the mantle over the past 4.5 billion years formed the continental crust, and produced at least one complementary melt-depleted reservoir that is now recognized as the upper-mantle source of mid-ocean-ridge basalts1. However, geochemical modelling and the occurrence of high 3He/4He (that is, primordial) signatures in some volcanic rocks suggest that volumes of relatively undifferentiated mantle may reside in deeper, isolated regions2. Some basalts from large igneous provinces may provide temporally restricted glimpses of the most primitive parts of the mantle3,4, but key questions regarding the longevity of such sources on planetary timescales—and whether any survive today—remain unresolved. Kimberlites, small-volume volcanic rocks that are the source of most diamonds, offer rare insights into aspects of the composition of the Earth’s deep mantle. The radiogenic isotope ratios of kimberlites of different ages enable us to map the evolution of this domain through time. Here we show that globally distributed kimberlites originate from a single homogeneous reservoir with an isotopic composition that is indicative of a uniform and pristine mantle source, which evolved in isolation over at least 2.5 billion years of Earth history—to our knowledge, the only such reservoir that has been identified to date. Around 200 million years ago, extensive volumes of the same source were perturbed, probably as a result of contamination by exogenic material. The distribution of affected kimberlites suggests that this event may be related to subduction along the margin of the Pangaea supercontinent. These results reveal a long-lived and globally extensive mantle reservoir that underwent subsequent disruption, possibly heralding a marked change to large-scale mantle-mixing regimes. These processes may explain why uncontaminated primordial mantle is so difficult to identify in recent mantle-derived melts.

Nixonite (IMA 2018-133), ideally Na2Ti6O13, is a new mineral found within a heavily metaso-matized pyroxenite xenolith from the Darby kimberlite field, beneath the west-central Rae Craton, Canada. It occurs as microcrystalline aggregates, 15 to 40 mm in length. Nixonite is isostructural with jeppeite, K2Ti6O13, with a structure consisting of edge- and corner-shared titanium-centered octahedra that enclose alkali-metal ions. The Mohs hardness is estimated to be between 5 and 6 by comparison to jeppeite, and the calculated density is 3.51(1) g/cm(3). Electron microprobe wavelength-dispersive spectroscopic analysis (average of 6 points) yielded: Na2O 6.87, K2O 5.67, CaO 0.57, TiO2 84.99, V2O3 0.31, Cr2O3 0.04, MnO 0.01, Fe2O3 0.26, SrO 0.07, total 98.79 wt%. The empirical formula, based on 13 O atoms, is: (Na1.24K0.67Ca0.06)S-1.97(Ti5.96V0.023Fe0.018)S6.00O13 with minor amounts of Cr and Mn. Nixonite is monoclinic, space group C2/m, with unit-cell parameters a = 15.3632(26) angstrom, b = 3.7782(7) angstrom, c = 9.1266(15) angstrom, b = 99.35(15)degrees, and V = 522.72(1) angstrom(3), Z = 2. Based on the average of seven integrated multi-grain diffraction images, the strongest diffraction lines are [d(obs) in angstrom (I in %) (hkl)]: 3.02 (100) (310), 3.66 (75) (110), 7.57 (73) (200), 6.31 (68) (20 (1) over bar), 2.96 (63) (31 (1) over bar), 2.96 (63) (20 (3) over bar), and 2.71 (62) (402). The five main Raman peaks of nixonite, in order of decreasing intensity, are at 863, 280, 664, 135, and 113 cm(-1). Nixonite is named after Peter H. Nixon, a renowned scientist in the field of kimberlites and mantle xenoliths. Nixonite occurs within a pyroxenite xenolith in a kimberlite, in as-sociation with rutile, priderite, perovskite, freudenbergite, and ilmenite. This complex Na-K-Ti-rich metasomatic mineral assemblage may have been produced by a fractionated Na-rich kimberlitic melt that infiltrated a mantle-derived garnet pyroxenite and reacted with rutile during kimberlite crystallization.

The Comment by Kostrovitsky & Yakovlev aims to demonstrate that Abersteiner et al. (2018) ‘presented erroneous statements regarding the genesis’ of the mineralogically and geochemically unique Serpentine-Free Udachnaya-East (SFUE) kimberlite (Russia) as it contradicts the views presented by Kostrovitsky et al. (2013). Furthermore, these authors reassert that ‘the supposition that surfaces salts and sulphates represent the main source for Na–Cl–S mineralization of kimberlites with unaltered olivine (Kostrovitsky et al., 2013) is still valid’ and ‘the mantle origin of salts is doubtful’. Numerous hypotheses are presented in both Kostrovitsky & Yakovlev (Comment) and Kostrovitsky et al. (2013) advocating a crustal brine origin for salts in the SFUE kimberlite. However, we find these interpretations to be poorly substantiated by empirical evidence and often contradictory. It is, therefore, important to revisit the earlier publication by Kostrovitsky et al. (2013) that is used to support the Comment by Kostrovitsky & Yakovlev. Here we address some of the erroneous and contradictory points presented by Kostrovitsky et al. (2013), which render their interpretations tenuous and misleading: Presence of evaporites in country rocks: Kostrovitsky et al. (2013) contradict themselves by suggesting that evaporites in the country rocks are both present and absent at the Udachnaya-East kimberlite. These authors stated that the Udachnaya-East kimberlite ‘does not intersect massive evaporites’ (p. 77), but later claimed that ‘...the highest (8 vol %) abundance of halite is restricted to depth levels of southern diatremes (Mir, Udachnaya, and International’naya) where they cut through halite-rich evaporite’, (p. 84) and ‘The absence of all textural types of serpentine in SFUE kimberlite is easily explained by the model of the evaporite country rock contamination’ (p. 88). The published and unpublished reports for parametric and geotechnical drill holes [figures 1 and 2 of Kamenetsky et al. (2014)] showed no evidence of sedimentary evaporite beds in or around the Udachnaya-East kimberlite. The composition of the putative kimberlite melt: The composition of the melt that is supposedly parental to Udachnaya-East was suggested by Kostrovitsky et al. (2013) to have resulted from ‘assimilation of evaporite xenoliths at relatively high, magmatic temperatures producing hybrid melt with elevated contents of Na, K, Cl, and S’, (p.88) and that ‘the hybrid residual kimberlite that digested evaporite xenoliths had lower H2O activity due to increased halogen and alkali abundances’ (p. 88). However, these authors also stated that ‘the contents of H2O, Na2O, and, by inference, the mode of halite are thus controlled only by the spatial position of the kimberlite specimen, rather than by the composition of the kimberlite melt’. Again, Kostrovitsky et al. (2013) did not present a consistent view as to whether salt was controlled by assimilation of alleged ‘evaporites’ or by the spatial position of the kimberlite rock. Primary versus secondary enrichment in Na and Cl: (Kostrovitsky et al., 2013) again presented conflicting views on the origin of Na and Cl mineralisation. On the one hand, these authors considered Na and Cl to be primary magmatic: ‘Na-rich kimberlite compositions are not solely restricted to unserpentinized kimberlites and that groundmass serpentine does not replace primary alkali- and chlorine-bearing minerals’. (p. 84), and ‘...alkali-, sulfur-, and chlorine-rich minerals may have crystallized from this late hybrid melt and may be "comagmatic" with kimberlite’ (p.88), but on the other hand they pushed for their secondary origin: ‘the strongest evidence for the secondary origin of Na-, Cl-, and S-rich minerals in the Udachnaya-East kimberlite... is the regional correlation between the geology and hydrogeology of the local country rocks and the mineralogy of Yakutian kimberlites’ (p.86). With this preface, we discuss below the Comment by Kostrovitsky & Yakovlev, and emphasise that previous data and interpretations by Abersteiner et al. (2018b) and other works are still valid and concordant with a magmatic origin of alkalis and halogens in the SFUE kimberlite.

The ca. 1153 Ma Premier kimberlite pipe on the Kaapvaal craton has been intruded by late-stage kimberlite and carbonatite magmas forming discrete 0.5 to 5 m wide dykes within the lower diatreme. On the basis of petrography and geochemistry, the fresh kimberlite dykes represent archetypal monticellite phlogopite kimberlite of Group-1 affinity. Their mineral compositions, however, show marked deviations from trends that are typically considered as diagnostic for Group-1 kimberlite in mineralogical-genetic classification schemes for volatile-rich ultramafic rocks. Groundmass spinel compositions are transitional between magnesian ulvospinel (a Group-1 kimberlite hallmark feature) and titanomagnetite trends, the latter being more diagnostic for lamproite, orangeite (formerly Group-2 kimberlite), and aillikite. The Premier kimberlite dykes contain groundmass phlogopite that evolves by Al- and Ba-depletion to tetraferriphlogopite, a compositional trend that is more typical for orangeite and aillikite. Although high-pressure cognate and groundmass ilmenites from the Premier hypabyssal kimberlites are characteristically Mg-rich (up to 15 wt% MgO), they contain up to 5 wt% MnO, which is more typical for carbonate-rich magmatic systems such as aillikite and carbonatite. Manganese-rich groundmass ilmenite also occurs in the Premier carbonatite dykes, which are largely devoid of mantle-derived crystal cargo, suggesting a link to the kimberlite dykes by fractionation processes involving development of residual carbonate-rich melts and fluids. Although mineralogical-genetic classification schemes for kimberlites and related rocks may provide an elegant approach to circumvent common issues such as mantle debris entrainment, many of the key mineral compositional trends are not as robust for magma type identification as previously thought. Utilizing an experimentally constrained CO2-degassing model, it is suggested that the Premier kimberlite dykes have lost between 10 and 20 wt% CO2 during magma ascent through the cratonic lithosphere, prior to emplacement near the Earth's surface. Comparatively low fO2 values down to −5.6 ∆NNO are obtained for the kimberlite dykes when applying monticellite and perovskite oxybarometry, which probably reflects significant CO2 degassing during magma ascent rather than the original magma redox conditions and those of the deep upper mantle source. Thus, groundmass mineral oxybarometry may have little value for the prediction of the diamond preservation potential of ascending kimberlite magmas. After correction for olivine fractionation and CO2-loss, there remains a wide gap between the primitive kimberlite and carbonatite melt compositions at Premier, which suggests that these magma types cannot be linked by variably low degrees of partial melting of the same carbonated peridotite source in the deep upper mantle. Instead, fractionation processes produced carbonate-rich residual melts/fluids from ascending kimberlite magma, which led to the carbonatite dykes within Premier pipe.

Determining whether magma fragments during eruption remains a seminal challenge in volcanology. There is a robust paradigm for fragmentation of high viscosity, silicic magmas, however little is known about the fragmentation behaviour of lower viscosity systems—the most abundant form of volcanism on Earth and on other planetary bodies and satellites. Here we provide a quantitative model, based on experiments, for the non-brittle, fluid dynamic induced fragmentation of low viscosity melts. We define the conditions under which extensional thinning or liquid break-up can be expected. We show that break-up, both in our experiments and natural eruptions, occurs by both viscous and capillary instabilities operating on contrasting timescales. These timescales are used to produce a universal break-up criterion valid for low viscosity melts such as basalt, kimberlite and carbonatite. Lastly, we relate these break-up instabilities to changes in eruptive behaviour, the associated natural hazard and ultimately the deposits formed., Determining if a volcanic eruption will behave effusively or explosively is crucial for predicting the potential hazard type and for planning effective mitigation. Here, the authors present a universal, fluid dynamic induced, break-up criterion for low viscosity melts.

The Kundelungu Plateau in the southeast of the Democratic Republic of the Congo (DRC) hosts numerous kimberlites, but up to now, only 34 bodies have been mapped. Locating these occurrences is hampered by the presence of sand cover on the plateau, a few tens of meters thick. Thus, most of the known pipes occur at the edge of the plateau where erosion has removed most of the sand cover. We report here on the Katuba kimberlite, a volcaniclastic kimberlite typical of a diatreme environment, with xenoliths of peridotite, carbonate, sandstone and shale, and lapilli-like microstructures. U-Pb analysis of perovskites from the Katuba kimberlite provides an age of 23 ± 1.8 Ma for the intrusion. Considering the age of 33 ± 4 Ma for perovskites from the Msipashi kimberlite pipe (also located on the same plateau), this new age suggests that the kimberlite magmatism in the Kundelungu Plateau lasted at least for 10 myr. The emplacement of these kimberlites is coeval with the opening of the Mweru graben, which is part of the East African Rift System (EARS), with structures oriented generally NW-SE and NE-SW. Some copper mineralisations inside the Katanga copperbelt, including those at Dikulushi and Kipushi, are located in similar structures, suggesting that the fluids responsible for the remobilisation of the mineralisation may be related to the kimberlite magmatism. Alternatively, the trigger for both the remobilisation of the mineralisation and the kimberlite magmatism is the tectonism that lead to the opening of the EARS. The upwelling of the asthenosphere or the mantle plume associated with the kimberlite magmatism may have supplied sufficient heat for fluid generation or contributed to the remobilisation of fluids. The location of the Katuba kimberlite along the NW-SE structures that were reactivated during the rifting inducing the opening of the Mweru graben, and which themselves are crosscut by the Luizi impact structure, provides another constraint on the relative age of the Luizi structure, which must be younger than the NW-SE structures and older than the emplacement of the Katuba kimberlite.

The Bundelkhand craton is surrounded by different mobile belts. The central Indian tectonic zone (CITZ) in the southern part is one of the prominent tectonic zones. CITZ is an important structural controlling factor for the Majhgawan and Hinota Kimberlite pipes. Several dyke swarms and quartz vein fractures are resulted due to volcanic and tectonic activity in the present study area. The objective of the present study is to delineate the subsurface lineaments using different edge enhancement techniques for mineral exploration in the future. Initially, First vertical derivative (FVD), total horizontal derivative (THD), tilt derivative (TDR) and theta (THETA) map have been applied to EIGEN6C4 Bouguer anomaly data. Composite lineament density map has been generated using all enhanced maps to analyze the effect of length of lineaments in the unit area. Upward continuation maps for different height have been generated to distinguish the shallower and deeper body effects. Further, Euler 3D deconvolution technique has been applied to Bouguer anomaly data to calculate the possible depth of associated lineaments. A comparative analysis of upward continuation depth and Euler’s depth has been carried out zone wise.