We know that tectonomagmatic activity periodically increased during the Earth’s history without any visible external factors to cause these occurrences. This is obviously related to the evolution of petrological processes at depth that produce events in the outer shells of the modern Earth (the tectonosphere). However, the essence of these processes and the mechanisms that translate them to the tectonosphere remain little known. We have examined this problem for the particular case of the Late Cenozoic (Neogene to Quaternary) global activation. We know that the modern Earth is a cooling body with a solidifying liquid iron core. The process must be accompanied by a number of thermodynamic, physical, and physicochemical effects, and it is these which might cause the inner activation of our planet. We have tried to shed some light on these problems using available modern geological, petrological, geochemical, and geophysical data on the activation that is just now occurring before our eyes. We have shown that the main active element on the modern Earth must be a thin crystallization zone that is constantly rising; that zone is between the wholly solidified part of the core (the solid inner core) and its completely liquid part (the outer liquid core). It is this zone which harbors various phase transitions in a cooling melt as the melt is passing bifurcation points. The phase transitions are both of the type like a change in released solid phases that accrete to the inner core and as retrograde boiling producing drops of core fluids. It is shown that the drops are rising in a high-Fe host melt and are accumulated at the base of the mantle. Once there, they participate in the generation of mantle plumes which are the chief translators of deep impulses to the outer geospheres, and leave the core for good simultaneously with impulses. It is supposed that at one such point, fluid solubility experienced a sharp drop in the cooling high-iron liquid of the outer core. This must have led to a simultaneous intensification of retrograde boiling of this melt throughout the entire surface of the core crystallization zone, that is to say, on a global scale. It is this phenomenon which must have supplied the excess of core fluids necessary for mass generation of mantle plumes and have served as a trigger for processes involved in the Late Cenozoic global tectonomagmatic activation of the Earth.

It is known that the Earth’s history is characterized by periodic activation of tectonomagmatic processes, when they are intensified without visible reasons. This is obviously related to the evolution of deep-seated petrological processes, the peculiar reflect of which are events in the external shells of the modern Earth (tectonosphere), but the nature of these processes and mechanisms of their translation in tectonosphere remain weakly studied. This problem is considered by the Late Cenozoic (Neogene–Quaternary) global activation. The modern Earth represents a cooling body with solidifying liquid iron core. This process should be accompanied by several thermodynamic, physical, and physical-chemical effects, which could lead to the internal activation of our planet. We attempted to decipher these problems using available geological, petrological, geochemical, and geophysical data on the present-day activation. It is shown that main active element in the modern Earth is uninterruptedly upward moving thin crystallization zone located between completely solidified part of the core (solid inner core) and its completely liquid part (external liquid core). Diverse phase transitions in a cooling melt passing through bifurcation points are related to this zone. The phase transitions are represented by both a change of crystallizing solid phases which built up inner core and retrograde boiling with formation of drops of “core” fluids. These drops are floated in high-Fe host melt and are accumulated at the mantle base, where they are involved in the formation of mantle plumes, which are the main carriers of deep-seated pulsed into external geosphere, and finally leave the core with them. It is suggested that in one of such points the fluid solubility in cooling high-Fe liquid of external core sharply decreases. This should lead to the simultaneous intensification of retrograde boiling of this melt over the entire zone surface of zone of the core crystallization zone, i.e., on a global scale. This could provide the influx of excess “core” fluids required for large-scale generation of mantle plumes and serve as trigger for Late Cenozoic global tectonomagmatic activation of the Earth.

The paper addresses megacrysts of “bubbly” kaersutite found among mantle xenoliths in the Al Ghab plateau basalts, northwestern Syria. The xenoliths as all xenoliths worldwide are represented by two series: green spinel peridotites (mainly lherzolites) and cross-cutting veins rocks of “black series” (mainly kaersutite hornblendites and kaersutite clinopyroxenites). It is believed that the parental melts/fluids of the “black series” were formed under decompressional fluid-assisted melting of the plume’s spinel peridotites at the late stages of development of the plume-related magmatic systems. “Bubbly” kaersutite megacrysts are fragments of pegmatoid varieties of the “black series” rocks. They represent monocrystals up to 10 cm long, which contain numerous relatively large cavities partially filled with volcanic dust. It is shown that the “bubbly” structure of these megacrysts is explained by their crystallization during retrograde boiling of parental melt/fluid in the mantle plume head at a pressure of 9–10 kbar. The oval cavities initially represented bubbles of high-density carbon dioxide entrapped by growing crystals. These bubbles were likely degassed during eruption and CO2 has been partially preserved only in some microscopic bubbles. It was also shown that the parental melt contained small suspended drops of fluid-saturated high-Fe liquid, which were likely derived through liquid immiscibility before retrograde boiling of the melt/fluid.

This paper synthesizes available and original U-Pb geochronological and hafnium and oxygen isotope data on zircon from gabbro and peridotites in the oceanic core complexes (OCC) of the Mid-Atlantic Ridge (MAR) extending for 2000 miles along its crest zone. We attempted to reproduce the evolution of MAR magmatism and to determine the geochemical and geodynamic nature of zircon protolith in OCC. We show that the relicts of old continental lithosphere have been preserved locally beneath the axial ridge zone and were involved in the partial melting of a shallow mantle during the entire magmatic evolution of the MAR rift valley. Age variations of zircon from plutonic rocks of the oceanic basement of fracture zones at some distance from the rift valley suggest young magmatism that differs in age from established magnetic anomalies. During the geological history of the Atlantic Ocean, the evolution of the melt originated in the rift valley of MAR, with zircon crystallization at the final stages, was influenced by aqueous (or aqueous–saline) fluid. Obtained conclusions confirm the fundamental significance of the interaction between hydrothermal and magmatic systems in the slow-spreading mid-ocean ridges.

The paper reports first comprehensive geological, petrographic, mineralogical, and geochemical data on one of the world’s oldest Tiksheozero ultramafic‒alkaline‒carbonatite complex (~1.99 Ga), which belongs to the Mid-Paleoproterozoic igneous province of the Baltic Shield. The complex was formed in three intrusive phases. The first phase is composed of the low-alkali mafic‒ultramafic rocks: dunites, wehrlites, clinopyroxenites, and gabbro. The rocks of the second phase are alkaline ultramafic rocks represented mainly by jacupirangites (alkaline clinopyroxenites) and foidolites (melteigites, ijoliltes, and urtites), with subordinate olivinites, alkaline gabbro, and nepheline syenites. The third intrusive phase is made up of carbonatites. Geochemical and mineralogical data indicate that all three phases were derived from different primary melts. It is shown that the nepheline syenites were obtained by fractionation of foidolites. A model of formation of such complexes through decompressional melting of mantle plume head enriched in carbonate fluid is proposed.

One of the main natural disasters is explosive volcanic eruptions, often lasting 2–4 months. It is obvious that such eruptions of volcanoes cause simultaneous mass release of gas bubbles from the melts of their shallow peripheral chambers, which must lead to a sharp increase in the volume of material contained in them, i.e., to explosions. It is shown that the main prerequisite for an explosive eruption is a sharp decrease in the solubility of water in melts known from experimental data at pressures less than 1 kbar corresponding to a depth of 3.5 km (Shilobreeva et al., 1991). Therefore, rising water-saturated melts characteristic of suprasubduction (convergent) settings, automatically become supersaturated with water when they reach depths of 3–4 km, and are thus an explosive mixture that is ready to blow up at any moment. However, the release of gas bubble nuclei is a very energy-consuming process, and will not begin by itself. We believe that the trigger for a catastrophic explosion can be one of the earthquakes preceding the eruption, which resonates with self-oscillations in the peripheral chamber beneath the volcano. This greatly increases the power of the impulse and helps to overcome the energy barrier. It is shown that the necessary and sufficient conditions for the occurrence of a catastrophic eruption are: 1) the existence of a shallow chamber with a water-supersaturated magma melt; the presence of other volatiles (CO2, SO3 etc.) does not play a significant role here; 2) the occurrence of a triggering earthquake that is in resonance with self-oscillations in this chamber; and 3) the presence of a continuous supply of the peripheral chamber beneath the active volcano with new melt portions, thus prolonging the eruption.

We have investigated the compositional variations of apatite (Ap) and rare-earth element (REE) minerals in the Monchepluton layered complex on the Kola Peninsula. On the basis of large sets of pertinent analytical data, we have estimated geochemical trends involving major, minor, and trace elements and studied their relation with the compositions of rock-forming silicate and oxide minerals. The variations observed in Ap differ considerably from trends reported for other layered intrusions. The composition fields of Ap are not consistent with the variations in the chemical composition of the bulk rocks and their constituent minerals, as determined along the representative cross sections of the entire complex. The compositional variations of Ap are fairly similar in all units of the complex. Chlorapatite (>6 wt.% Cl) is invariably abundant. There is no relationship between the Cl content of Ap and the degree of magnesium enrichment of the coexisting early magmatic silicates. In the F-Cl-OH diagram, broad fields of ternary solid solution are observed. There are no compositions along the Cl-F axis. The compositions of Ap are notably poor in Cl in the marginal series (the Nyud massif) and correspond to hydroxylapatite with a high content of fluorapatite component. Two composition fields of Ap are recognized in the Monchepluton complex: <= 3 wt.% and >6 wt.% Cl; there are, however, extensive overlaps. Two generations of apatite are thus implied. The first nucleated at the early stage of crystallization of H2O-bearing intercumulus melt as a result of substantial increase in the contents of P, F, Cl, and other incompatible components. The following stage of degassing of the crystallizing melt caused a decoupling of Cl and F. Fluorine remained mostly in the melt; in contrast, Cl was partitioned efficiently into an H2O-bearing fluid phase. At the early stage, the apatite incorporated combinations of hydroxylapatite and fluorapatite, with a low content of Cl. At the late stage, chlorapatite crystallized from a Cl-rich fluid, and ferrochlo-ropargasite (4.1 wt.% Cl) formed in the Poaz massif as a result of autometasomatic alteration via reactions of this fluid with plagioclase and pyroxene. The apatite has high Sr contents (up to 4.1 wt.% SrO) in the highly magnesian cumulates of the Dunite block and the massifs of mounts Kumuzh'ya, Nittis, and Travyanaya. This enrichment illustrates the accumulation of Sr in the intercumulus melt, in which Ap was the only Sr-bearing phase in the absence or scarcity of intercumulus plagioclase. The REE contents also increased in the intercumulus melt and led to the formation of monazite-(Ce), REE-bearing Ap, and allanite-(Ce) in the remaining microvolumes of melt. Loveringite and Ap crystallized as coexisting phases in Mt. Sopcha. For the first time in a layered intrusion, an extensive range of compositions is documented in the Ce-La-Nd diagram for the REE-bearing phosphates (monazite and REE-rich apatite), which display a predominant La <-> Nd substitution at the constant contents of Ce.

Proterozoic magmatism (2.5 ± 0.1 to 1.0 ± 0.1 Ga ago) represents a very important transition from the magmatism of the early stages of the Earth's evolution to the Phanerozoic magmatism that continues to the present day. The type of tectonomagmatic activity in all the Precambrian shields allows the Proterozoic to be clearly divided into two radically different stages: from 2.5 to 2.2–2.0 Ga ago, and from 2.0 to 1.0 Ga ago, differing both in their type of magmatic processes and in their geodynamics. The Baltic Shield is the largest Precambrian basement inlier of the Russian Platform. According to Kratz et al., it is divided into four geoblocks of differing ages: the Caledonian, Dahlsland, Svecofennian and Kola–Karelian. The volcanic and intrusive rocks of the eastern Baltic Shield are related to the so-called Karelides, emplaced during the Karelian, or Sumian–Sariolian, tectonomagmatic cycle.

The study of the evolution of large igneous provinces showed that the Archean and Early Paleoproterozoic mantle plumes were formed by high-Mg ultramafic rocks and looked like thermal plumes. However, this situation experienced a cardinal change in the mid-Paleoproterozoic ~2.3 Ga, when an irreversible change occurred in the composition of these plumes, providing evidence of an essentially new, geochemically enriched material being involved in the tectonomagmatic processes. Thermochemical plumes like these still exist today and, according to the modern paradigm, they are generated as the lowermost mantle is supplied with fluids released from the liquid outer core. This is in good agreement with the data on the material composition of these plumes containing both fragments of depleted ultramafic rocks of the mantle matrix (green spinel peridotites, mostly lherzolites) and veins of geochemically enriched rocks that were formed during incongruent melting of plume material due to fluids of core origin that were part of the plume material. It is shown that the magmatism during the first half of the Earth’s history (Protogean) was different from that of the second half (Neogean) in being nearly completely devoid of elements related to the core-derived fluids (Ti, Nb, Ta, alkalies, etc.). Possible factors that have contributed to this evolution are considered. We discuss the effect this change has had on the tectonomagmatic processes, and on the ecology and evolution of the biosphere. That is to say, we show how events in the Earth’s deep interiors affect to the surface processes. We show that the amazing stability of mantle plume composition during the last 2.3 billion years is more likely due to the fact that, in this case, crystallization in the core releases fluid components, which control the character of the intraplate magmatism throughout the Neogean. These fluids are constantly released from the solidifying liquid core along with newly generated mantle plumes, thus providing for stability in the composition of the latter.

The magmatism of Phanerozoic orogenic and anorogenic regions is closest to that of the present day. Ophiolite assemblages are typical of the earliest stages of fold-belt evolution. The reconstruction of the initial tectonic position of ophiolites is of major importance for the geodynamic interpretation of the early stages of fold-belt formation. Certainly, the presence within the ophiolites of sheeted dyke complexes, which indicate consolidation of the assemblage during intense sea-floor spreading, is of crucial importance in the interpretation of ophiolites. On the present-day Earth's surface, these conditions occur in mid-oceanic rifts and back-arc spreading centres in island arc–marginal sea systems. Extensive geochemical studies of ophiolitic lavas have shown that two main groups of basalts can be distinguished in ophiolites. These correspond with: volcanics of oceanic rifts or those of spreading zones in marginal seas; and volcanics of island arcs.

The Archaean, which spans the time from the formation of the Earth to c. 2600 Ma ago, was a time of crucial importance in the formation of the Earth's crust and mantle. The most ancient dates on Archaean formations were obtained from detrital zircons from Archaean metasediments. The upper boundary of the transition from an Archaean type of geodynamics and magmatism to a Proterozoic type remains the subject of debate. Within the ancient shields two types of Archaean structural terrane have been distinguished: granite–greenstone and granulite–gneissic. They differ in their internal structure, their structural and metamorphic history, the ratio of exogenetic to endogenetic factors in the generation of crustal material and the type and form of the igneous activity and metallogeny. Archaean granite–gneiss areas are generally composed of 80–90% peculiar "grey gneisses", which are actually plagiogneisses of tonalite–trondhjemite-granodiorite composition.

Recent evidence suggests that magmas are generated from both mantle and crustal material. Thus both basic and ultrabasic magmas are derived from ultra-basic mantle material, acid magmas are derived from crustal material, and magmas of intermediate composition may have a mixed mantle and crustal source. In recent years, two major trends have been outlined in the study of the petrology and geochemistry of subcrustai zones. The first is based on study of the composition and equilibrium P–T conditions of deep-seated rocks that are solid when they reach the surface. The basis of another concept is the generally accepted theory that the mantle is the source region for various types of magma. Peridotite type I is conventionally termed an undepleted undifferentiated ("chondritic") peridotite. Although the present-day Earth's lithosphere is heterogeneous, there are good reasons to believe that a large variety of subcrustal rocks were formed from roughly homogeneous primordial mantle material.

The Arbansky massif (~70 km^, thickness 1 km) is located in 150 km to northwest from Lake Baikal in the bordering Prisayanian uplift of the Siberian platform Precambrian basement.The uplift formed by 2 large structures: Sharyzhalgay block which formed by the early proterozoic (2.5-2.4Ga) granulite complex, and Onotsky graben -fragment of the late archean granite-greenstone terrane (fig.1).

—Our study of mantle xenoliths in the Cretaceous lamprophyre diatremes and late Cenozoic plateau basalts of western Syria has shown that the ancient lower crust that existed in the Cretaceous and was composed of garnet granulites and eclogite-like rocks was replaced by mantle peridotites in the late Cenozoic. We conclude that the heads of the local (secondary) plumes of the present-day Afro-Arabian thermochemical mantle plume responsible for the regional basaltic magmatism reached the basement of the ancient upper sialic crust, where they spread, leading to a displacement of the mafic lower crust.