В монографии обобщены результаты исследований по геологии, петрографии. минералогии, геохимии и условиям образования различных типов высокобарических пород-эклогитов, эклогитоподобных пород, эклогит-глаукофановых и глаукофановых сланцев и жадеититов, В основу положены материалы по высокобарическим комплексам Южного Урала, Северного Казахстана и юга Алданского щита. Рассмотрены вопросы систематики, закономерности локализации, динамики формирования и последующих преобразований этих пород.
Для геологов, минералогов, петрографов и геохимиков.

Early Precambrian eclogites are widespread in the Belomorian Province of the Fennoscandian shield. There are three points of view on the their age: 1) Archean and Paleoproterozoic; 2) solely Mesoarchean; 3) solely Paleoproterozoic. The goal of this field trip is to show all these types of eclogites including Archean and Paleoproterozoic (from the authors' point of view) eclogites, eclogitized Paleoproterozoic coronitic gabbroids, Archean zoisitites and their structural position in the Gridino, Salma (Uzkaya Salma and Shirokaya Salma) and Kuru-Vaara areas of the Belomorian Province. The geological excursions provide a good opportunity for the participants and the reader to exanimate these contradicting points of view immediately at beautiful outcrops on islands of the White Sea, on the benches of the Kuru-Vaara quarry and in the walls of road pits in the Salma area. This Field Guidebook is of interest for geologists, petrologists and geochronologists who study the early evolution of the Earth and HP-UHP metamorphic processes 

Сборник включает статьи, посвященные различным аспектам исследования метаморфических процессо, осуществляющихся в самых широких диапазонах изменения Р-Т-параметров. Серия статей касается процессов образования эклогитов и глаукофановых сланцев, вторичной калишпатизации и альбитизации в областях молодого и современного вулканизма Курило-Камчатской зоны. Значительное место отводится вопросам генетической минералогии и кристаллохимии: изучению особенностей химизма и условий образования силикатных минералов, теории изоморфизма в классе силикатов и др. Особый раздел посвящен баро- и термометрическим исследованиям

В монографии обобщены новые материалы по геологическому строению, минералогии, петрографии и геохимии эклогитсодержащих и глаукофансланцевых комплексов, а также приведены материалы по эклогитоподобным и другим ассоциирующим породам. Делается сопоставление со складчатыми поясами различных регионов мира и на основе всего имеющегося материала обсуждаются проблемы генезиса эклогитов и глаукофановых сланцев. Особое внимание обращено на факты, указывающие на необычно высокие давления, достигаемые при метаморфизме пород земной коры.

Книга рассчитана на геологов, петрологов. геохимиков

Austrheim, H. and Griffin, W.L., 1985. Shear deformation and eclogite formation within granulite-facies anorthosites of the Bergen Arcs, western Norway. In: D.C. Smith, G. Franz and D. Gebauer (Guest-Editors), Chemistry and Petrology of Eciogites. Chem. Geol., 50: 267—281.

The anorthosites of the Bergen Arcs contain two distinct metamorphic mineral assemblages which are stable under different P—T conditions. A granulite-facies assemblage, which equilibrated at T = 800—900° C, P < 10 kbar, is defined by the minerals plagioclase, Al-rich diopside (Cpx I), garnet (Gnt I) ± scapolite ± orthopyroxene + dark-brown hornblende. This assemblage is linked by corona structures to a primary mag-matic mineralogy, where coexistence of olivine and plagioclase limits the maximum crystallization pressure of the anorthosites to ~ 8 kbar at 1200°C. The anorthosites are transected by a series of fine-grained shear zones in which the granulite-facies assemblage is replaced by an eclogite mineralogy defined by omphacite (Cpx II) (Jd40_i0) + garnet + kyanite + epidote/clinozoisite + phengite + quartz ± amphibole with plagioclase sometimes remaining in the marginal parts. Mineral compositions indicate equilibration conditions for the eclogite paragenesis of Г = 700—800° С, Р = 16—19 kbar.

Изучение алмазов, находящихся в ксенолитах глубинных пород, и сравнение их с алмазами из кимберлитов имеют большое значение для решения вопроса об их генезисе. Установлено, что алмаз может обра­зовываться в двух различных геохимических обстановках: ультраоснов­ной (кимберлиты, ультраосновные глубинные включения) и основной (эклогитовые включения). Ю. Л. Орлов (1977), сопоставив кристалломорфологические особенности алмазов из кимберлитов и глубинных включений в них (как ультраосновного, так и эклогитового состава), пришел к выводу, что кристалломорфологический спектр алмазов во всех типах пород практически одинаков. С другой стороны, А.И. Пономаренко, описав мелкие бесцветные, серые и желтые кристаллы куби­ческого габитуса в алмазоносных эклогитах из кимберлитов, выделил их в качестве особого «эклогитового» типа алмазов.

Применение новых методов анализа и извлечения алмазов позво­лило заметно расширить наши знания об особенностях их кристалломорфологии и внутреннего строения. В частности, установлено, что в мелких классах крупности (менее 0,5 мм), которым практически не уделялось внимания, морфологический спектр алмазов заметно отли­чается от такового для более крупных классов (более 1 мм). <...>

This study aims at further understanding of the mechanisms how lattice-preferred orientations (LPO) develop during deformation in the main eclogite minerals. Microstructures and textures of deformed eclogites from the Les Essarts complex (Western France) were investigated using optical microscopy and electron backscatter diffraction (EBSD) in the scanning electron microscope. Microfabric analyses of eclogite-facies minerals are used to identify their deformation mechanisms, which define the rheology at high-pressure metamorphic conditions. Mechanisms of intracrystalline deformation by dislocation movement (dislocation creep) result usually in a non-linear flow law (typically power law), while diffusive processes (diffusion creep) correspond to linear flow laws. General microstructural observations may suggest intracrystalline deformation (dislocation creep) of omphacite. The omphacite LPO vary between S- and L-type and correlate with oblate or prolate grain shape fabrics, respectively. Until now, these LPO types have not been understood by plasticity models based on dislocation glide on the known slip systems in clinopyroxene. An alternative interpretation is given in terms of anisotropic growth and dissolution, with grain boundary diffusion as the rate controlling process. There are further indications suggesting diffusion creep with concomitant anisotropic growth and dissolution as a main deformation mechanism in omphacite. In omphacite around a hollow garnet, crystallographic and shape fabrics align with the c[001] axes parallel to the grain elongations defining the mineral lineation, which rotates locally with the inferred flow direction. In this part, the grain sizes of omphacite and rutile are larger than in the surrounding matrix. The geometry of both the shape and crystallographic fabrics is interpreted to represent the local stress regime (directions and ratios of the principal stresses). The LPO of rutile duplicate the LPO of omphacite and a similar distinction between S- and L-type was used. Rutile deformation mechanisms probably involve dislocation creep as well as diffusion creep. Quartz mainly occurs as an interstitial phase with weak LPO patterns interpreted as random. No representative obliquity of the LPO in omphacite nor rutile with respect to foliation and lineation was observed to be used as potential shear sense criteria. However, the rutile LPO was slightly rotated relative to the omphacite LPO consistently in most samples. The results suggest that diffusion processes are strongly involved in the deformation of eclogites. A linear flow law should be taken into account in tectonic models where eclogites are incorporated. 

An extended Vendian-Cambrian island-arc system similar to the Izu-Bonin-Mariana type is described in the Gorny Altai terrane at the margin of the Siberian continent.

Three different tectonic stages in the terrane are recognized. (1) A set of ensimatic active margins including subducted oceanic crust of the Paleo-Asian ocean, the Uimen-Lebed primitive island arc, oceanic islands and seamounts: the set of rocks is assumed to be formed in the Vendian. (2) A more evolved island arc comprising calc-alkaline volcanics and granites: a fore-arc trough in Middle-late Cambrian time was filled with disrupted products of pre-Middle Cambrian accretionary wedges and island arcs. (3) Collision of the more evolved island arc with the Siberian continent: folding, metamorphism and intrusion of granites occurred in late Cambrian-early Ordovician time. In the late Paleozoic, the above-mentioned Caledonian accretion-collision structure of the Siberian continent was broken by large-scale strike-slip faults into several segments. This resulted in the formation of a typical mosaic-block structure.

We consider the structural position and petrology of eclogites in the North Kokchetav accretion-collision zone located north of the Kokchetav metamorphic belt formed by high- and ultrahigh-pressure rocks. In the Early Ordovician North Kokchetav tectonic zone, thin sheets of mylonite and diaphthoric gneisses with eclogites are tectonically conjugate with the volcanic and sedimentary rocks of the Stepnyak paleoisland-arc zone. Eclogites have been revealed at two sites of the North Kokchetav tectonic zone—Chaikino and Borovoe. The Chaikino eclogites formed at 800–850 °C and 18–20 kbar, and the Borovoe eclogites, at 750–800 °C and 17–18 kbar. Study of pyroxene-plagioclase symplectite replacing omphacite of the eclogites at both sites has recognized three stages of regressive magmatism: (1) formation of coarse-grained clinopyroxene-plagioclase symplectite at 760–790 °C and 11–12 kbar, (2) formation of fine-grained clinopyroxene-plagioclase symplectite at 700–730 °C and 7–8 kbar, and (3) amphibolization of pyroxene at 570–600 °C and 5–6 kbar. The Ar-Ar age of muscovite from the Borovoe mica schists hosting eclogites is 493 ± 5 Ma, which corresponds to the time of cooling of metamorphic rocks to <370 °C. Hence, the peak of high-pressure metamorphism and all recognized stages of retrograde changes are dated to the Cambrian. The geological data evidence that eclogite-schist-gneiss sheets were localized in the accretion-collision zone and became conjugate with sedimentary and volcanic rocks no later than in the Middle Ordovician

The Kokchetav subduction-collision zone (KSCZ) hosting ultrahigh- and high-pressure (UHP-HP) rocks underwent the multistage Vendian-Early Ordovician geodynamic evolution. The subduction of the Paleoasian oceanic lithosphere bearing blocks of continental crust and the collision of the Kokchetav microcontinent with the Vendian-Cambrian island-arc system ultimately led to the formation and exhumation of UHP-HP rocks. In the Vendian-Early Cambrian the margin of the Kokchetav microcontinent deeply subsided into the subduction zone (150–200 km), which led to UHP-HP metamorphism (the maximum at about 535 Ma) and to partial melting of its rocks. In next stage (535–528 Ma), the generated acidic melts including blocks of UHP-HP rocks quickly, at a rate of 1 m/year, ascended to depths of 90 km for 1 Myr. During subsequent 5 Myr, the UHP-HP rocks ascending at a rate of 0.6–1 cm/year reached the base of the accretionary prism (depths of 60–30 km). Then, in the period from 528 to 500 Ma, the UHP-HP rocks ascended along the faulting structures of the lower crust as a result of jamming the subduction zone by the Kokchetav microcontinent. During the period from 500 to 480 Ma, the UHP-HP rocks became part of the upper crust. This process led to the KSCZ, which comprises terranes of the Vendian-Early Arenigian subduction zone occurring at different depths, separated by zones of garnet-mica and mica schists, blastomylonites and mylonites. In the same period there was a jump of subduction zone, which led to the formation of the Ordovician Stepnyak island arc. As a result of the Late Arenigian-Early Caradocian microcontinent-island arc collisions (480–460 Ma), the KSCZ overrided upon the fore-arc trough of the Stepnyak island arc to form a thick accretion-collision orogen, which having experienced anatectic melting was intruded by collisional granites of the Zerenda complex 460–440 Ma in age.