Larissa Dobrzhinetskaya

University of California, Riverside | UCR · Department of Earth and Planetary Sciences

Geologic and planetary processes are punctuated by sudden cataclysmic events, and planetary evolution is irrevocably changed by impacts and intense seismic and magmatic/volcanic activity. Such events often are associated with or generate high temperature, high pressure, and low oxygen fugacity. Their traces in the accessible geologic record are not...

Natural diamonds that have been partially replaced by graphite have been observed to occur in natural rocks. While the graphite-to-diamond phase transition has been extensively studied the opposite of this (diamond to graphite) remains poorly understood. We performed high-pressure and temperature hydrous and anhydrous experiments up to 1.0 GPa and...

Moissanite, SiC, is an uncommon accessory mineral that forms under low oxygen fugacity. Here, we analyze natural SiC from a Miocene tuff-sandstone using synchrotron Laue microdiffraction and Raman spectroscopy, in order to better understand the SiC phases and formation physics. The studied crystals of SiC consist of 4H-and 6H-SiC domains, formed fr...

By keenly probing mantle rheology, interactions of deformations and phase transitions, and microscopic features, he made major contributions to petrology, mineralogy, and earthquake science.

Here, we present studies of natural SiC that occurs in situ in tuff related to the Miocene alkaline basalt formation deposited in northern part of Israel. Raman spectroscopy, SEM and FIB-assisted TEM studies revealed that SiC is primarily hexagonal polytypes 4H-SiC and 6H-SiC, and that the 4H-SiC polytype is the predominant phase. Both SiC polytype...

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Moissanite (SiC), a high-pressure mineral of mantle origin, is a window into the oxygen deficiency processes in the deep Earth. There are also inexplicable reports of SiC in mineral separates from granites and other shallow rocks, and it should be revisited with obtaining SiC in situ. One of the newest and poor understood occurrences of abundant Si...

Minerals and Human Health is written in response to the demand for additional knowledge about global climate change, the industrial contamination of water reservoirs, and epidemiological intoxication from industrial hazards related to the use of mineral resources. The book addresses issues associated with the physical and geological processes of Ea...

The only direct samples of Earth's lower mantle are rare inclusions in diamonds. The most abundant are (Mg, Fe)O, showing highly magnesian compositions. Here we report a transmission electron microscopy study of an exceptional inclusion with composition ∼(Mg0.35Fe0.65)O, with 5–7 vol% nanometer-sized magnesioferrite spinel precipitated on dislocati...

The 1.85 Ga Belomorian Belt, Karelia, Russia, hosts ultralow δ18O and δD (as low as −27.3‰ and −235‰ standard mean ocean water [SMOW], respectively), high-Al gneisses and amphibolites that we attribute to the Paleoproterozoic “Slushball Earth” glaciation. They now occur in at least 11 localities spanning 450 km. To constrain distribution of 18O-dep...

Qingsongite (IMA 2013-30) is the natural analog of cubic boron nitride (c-BN), which is widely used as an abrasive under the name "Borazon." The mineral is named for Qingsong Fang (1939–2010), who found the first diamond in the Luobusa chromitite. Qingsongite occurs in a rock fragment less than 1 mm across extracted from chromitite in deposit 31, L...

The earliest period of Earth history is the Hadean era (4600–4000 Myr) but to date no rocks are known to be preserved from this time. However, abundant detrital zircons from the Archean Jack Hills conglomerate complex of Western Australia have been found with dates in excess of 4000 Myr and there is a significant literature concerning these zircons...

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Mr. President, Colleagues, and Guests: It is with great pleasure that I introduce Harry W. Green II, as recipient of the Mineralogical Society of America’s highest honor, the Roebling Medal. The Roebling Medal is awarded “for outstanding original research in mineralogy...defined broadly”—a description that completely fits Harry Green’s distinguish...

Previous studies showed that microdiamonds from Erzgebirge terrane of Germany are crystallized from a C-O-H fluid (Stoeckhert et al., 2001, 2009; Dobrzhinetskaya et al., 2003, 2007) due to course of the UHPM. Usually metamorphic diamonds are presented by single crystals of 5 to 80 micron size, which are caracterized by a complicated morphology sugg...

The upper mantle beneath the Alps and the Variscides of Central Europe has a varied seismic structure as a result of the accretionary and evolutionary processes that have shaped it. Natural earthquake data, the raypaths of which pass beneath these regions, have enabled the calculation of travel times out to 3000 km. The source-receiver geometry ens...

This is a comprehensive review paper devoted to microdiamonds from ultrahigh-pressure metamorphic (UHPM) terranes incorporated in orogenic belts formed at convergent plate boundaries in Paleozoic–Mesozoic–Alpine time. When in 1980 the first small diamonds were discovered within “amphibolite–granulate facies” metamorphic rocks, it came as a great su...

This is a comprehensive review paper devoted to microdiamonds from ultrahigh-pressure metamorphic (UHPM) terranes incorporated in orogenic belts formed at convergent plate boundaries in Paleozoic– Mesozoic–Alpine time. When in 1980 the first small diamonds were discovered within "amphibolite– granulate facies" metamorphic rocks, it came as a great...

Metamorphic diamonds from the Kokchetav massif in northern Kazakhstan are considered to have crystallized from a C–O–H fluid during ultra-high-pressure metamorphism of metasedimentary rocks subducted to 190– 280 km depth. Noble gases contained in the diamonds offer great potential to constrain the noble gas state of deep mantle reservoirs. Previous...

The concept of Ultra-High-Pressure Metamorphism (UHPM) grew out of the discovery that blueschist minerals in metasediments required simultaneous high pressure and low temperatures that, in turn, required rapid travel to several 10s of km to grow the minerals in the first place, and similarly rapid return to the surface to avoid their reaction to gr...

This chapter brings together an enigmatic petrogenetical problem, namely the origin of micro diamonds in the Kokchetav Massif, Kazakhstan (formed from CH4, CO2, graphite, carbonate, or CxOyHz…), and a powerful analytical method, namely Raman spectrometry. Raman mapping provides valuable information on the spatial distribution of the different miner...

The discovery of micro diamond, coesite, relicts of majoritic garnet, and other ultrahigh-pressure (UHP) minerals containing lamella exsolution of coesite and hydrous phases in rocks within continental collision terranes, suggests that buoyant continental materials can be subducted to depths > 250 km and returned to the Earth's surface. Unlike diam...

This chapter focuses on fundamental questions related to understanding global recycling of the subducted material, in terms of where the nonreturned continental material is stagnated, to what depth continental rocks of different bulk chemistry can be subducted, and how they can be recognized if their relicts or remainders are "assimilated" within u...

Geochemical characteristic of fluids circulating in deep subduction zones is of a great interest for many directions of geosciences. One of the intriguing processes is a fluid-rock interaction during subduction of the continental slab because the latter is characterized by contrast chemistry in comparison with the rocks of surrounding mantle and it...

In order to investigate the pressure implications of silica exsolution from clinopyroxene in ultrahigh-pressure metamorphic rocks, we have measured systematically the values of the Calcium-Eskola (Ca-Esk) component of clinopyroxenes over a considerable range of pressure and temperature. A series of anhydrous experiments using powdered glass of comp...

We report here the detailed microstructure and chemistry of pyroxene exsolution from a polycrystalline garnet porphyroblast of the Western Gneiss Region (WGR) garnet peridotite, Otrøy, Norway. For both clinopyroxene (Cpx) and orthopyroxene (Opx), the same basic crystallographic relationship is found with the host garnet: (100)py//{112}grt, (010)px/...

Metamorphic diamonds from the Kokchetav massif in northern Kazakhstan are considered to have crystallized from a C-O-H fluid during ultra-high-pressure metamorphism of metasedimentary rocks subducted to 190-280km depth. Noble gases contained in the diamonds offer great potential to constrain the noble gas state of deep mantle reservoirs. Previous s...

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This study explores the effects of metamorphism on luminescence of diamond. Four diamond suites extracted from metamorphic rocks were characterized using optical cathodoluminescence, FTIR spectroscopy, photoluminescence at the liquid nitrogen temperature, and cathodoluminescence spectroscopy. The studied diamonds are from sedimentary conglomerate a...

Ultrahigh pressure metamorphism (UHPM) is a relatively new but fast growing discipline related to the deep subduction of slabs of continental and/or oceanic crust into the Earth's mantle and their return towards the surface as important components of mountain belts. The discipline was established ~25 years ago after discoveries of high pressure min...

Inclusions of ferropericlase and Mg-wüstite frequently occur as inclusions in diamond from the lower mantle. Under mantle conditions, diamond plus inclusion are regarded as a closed system. Therefore, the original oxygen activity fo inside inclusions in diamond should have remained unchanged. Here, we report on TEM investigations on FIB-cut foils f...

The Alpe Arami garnet peridotite of the Southern Swiss Alps is associated with eclogites and included within quartzofeldspathic gneisses. Controversy has swirled around the depth of origin of this massif since the 1970s when application of the newly-developed technique of thermobarometry suggested a depth of last equilibration of greater than 120 k...

The study of δ 13CPDB (Pee Dee Belemnite) and nitrogen contents in 1 to 5-μm-diameter microdiamonds included in garnets from the quartz-feldspathic gneisses (Erzgebirge, Germany) was performed in situ with the Nano-scale Secondary Ion Mass Spectrometer. The results revealed that there were two stages of diamond crystallization from a C-O-H supecrit...

Recent studies of microdiamonds from orogenic belts related to continental collisions induced experimentalists to explore new crystallization media possible for diamond synthesis. This has led to considerable progress in diamond-synthesis experiments under high pressures and high temperatures. Diamond was found to grow in a wide variety of systems,...

Mössbauer spectroscopy was applied to study the valence state of iron in chromite from massive, nodular and disseminated podiform chromitite ores of the Luobasa ophiolite massif of Tibet. The results show that Fe3+/ΣFe = 0.42 in chromite from massive ore, and Fe3+/ΣFe = 0.22 in chromite from nodular and disseminated ores. The massive ore records tr...

Pyroxenes (Px) from ultrahigh pressure metamorphic terranes often contain SiO2 lamellae which are interpreted as a product of exsolution during decompression. Day & Milchahy (2007) showed that 3 types of reactions are responsible for releasing free SiO2 from Px: (1) vacancy consumption in non-stoichiometric Px; (2) dissolution of Ti-phases in Px an...

Ultrahigh pressure metamorphic rocks (UHPM) are an integral characteristic of collisional orogens, recording transient or even permanent subduction of continental margins into the mantle. Studies of these rocks in outcrops and laboratoris from microstructures, experimentally established phase transformations, mineral reaction kinetic principles to...

Diamond displays a supreme resistance to chemical and mechanical weathering, ensuring its survival through complex and prolonged crustal processes, including metamorphism and exhumation. For these reasons, volcanic sources and secondary and tertiary collectors for detrital placer diamonds, like Ural or Bingara diamonds, may be difficult to determin...

This is a review paper which summarizes recent achievements in studies of superdeep mantle rocks and diamonds from kimberlite and ultrahigh-pressure metamorphic (UHPM) terranes using advanced analytical techniques and instrumentations such as focused ion beam (FIB)-assisted transmission electron microscopy (TEM) and synchrotron-assisted infrared sp...

In the mid-1990s we recognized that collisional orogenic belts with UHP metamorphic rocks of crustal affinities, might contain mantle peridotites uplifted from depths of >300km (Dobrzhinetsklaya et al., 1996). We proposed that ilmenite rods + chromite flakes in olivine are the result of exsolution, and that they imply high solubility of TiO2 in Ol...

Inclusions of ferropericlase and Mg-wustite are frequently observed in diamond from the lower mantle. Diamond and inclusion are considered to form a closed system under mantle conditions. Therefore, the original oxygen activity fo inside inclusions in diamond remains constant. Here, we report on TEM investigations on FIB-cut foils of Mg-wustite inc...

Pyroxenes (Px) from ultrahigh pressure metamorphic terranes often contain SiO2 lamellae which are interpreted as a product of exsolution during decompression. Day & Milchahy (2007) showed that 3 types of reactions are responsible for releasing free SiO2 from Px: (1) vacancy consumption in non-stoichiometric Px; (2) dissolution of Ti-phases in Px an...

The pyroxene exsolution in garnet after majorite from garnet peridotites of Otrøy and Fjørtoft Islands suggests a very deep origin (>350 km) of the rocks. Microstructures and trace element compositions of the exsolved pyroxenes and garnets indicate that these ultra-deep mantle rocks may have experienced a complex multiple stage exhumation process....

An unusual mineral group was discovered in the Luobusa ophiolitic chromitite from the Yarlung Zangbu suture, Tibet, which was probably originated from the depth of over 300 km in the mantle. Minerals with distinguished deep impact include: coesite with pseudomorphs of stishovitem and diamond as individual grains or inclusion in OsIr alloy. Similar...

Metamorphic diamonds from the Kokchetav massif, northern Kazakhstan are considered to be crystallized from a C-O-H fluid during ultra-high pressure metamorphism of metasedimentary rocks subducted to the depth of 190-280 km [1]. The microdiamonds have been known for their “unprecedentedly” high 3He/4He of 6E-4 associated with very high He content [2...

The deepest rocks known from within Earth are fragments of normal mantle ( approximately 400 km) and metamorphosed sediments ( approximately 350 km), both found exhumed in continental collision terranes. Here, we report fragments of a highly reduced deep mantle environment from at least 300 km, perhaps very much more, extracted from chromite of a T...

Exsolution lamellae of pyroxene in garnet (grt), coesite in titanite and omphacite from UHPM terranes are widely accepted as products of decompression. However, interpretation of oriented lamellae of phyllosilicates, framework silicates and oxides as a product of decompression of pyroxene is very often under debate. Results are presented here of FI...

This widely accepted that fragments of deeply subducted continental and/or oceanic crust may return back from depth of 200-300 km to the surface as UHPM rocks forming collisional orogenic belts. These rocks containing UHP minerals or microstructural relics of their decompressions, as well as mantle xenoliths and diamonds from kimberlitic pipes, are...

In recent years ultrahigh pressure minerals, such as diamond and coesite, and other unusual minerals were discovered in chromitites of the Luobusa ophiolite in Tibet, and 4 new minerals have been approved by the CNMMN. These results have raised many questions

The combination of experimentation and microstructural analysis in the study of UHPM rocks is often the only way to unambiguously identify rocks that have been returned to the surface from great depth after very deep subduction. Identification of high-pressure phases such as coesite, diamond, or TiO2 II provide insight that a rock is properly chara...

It is widely accepted that fragments of deeply subducted continental and/or oceanic crust may return from depths ~200-300 km to the surface as UHPM rocks forming collisional orogenic belts. These rocks, containing UHP minerals or microstructural relics of their decompressions, as well as mantle xenoliths and diamonds from kimberlitic pipes, are val...

Among the light elements that have been added to mineral physics experiments concerning the Fe-rich core of the Earth, nitrogen is less favorable. In general, this is because metal-nitrides are thought to be rare within Earth. However this may not be because they are rare, but because nitrogen is difficult to detect by conventional electron micropr...

Analysis of 57Fe transmission Mössbauer spectra collected on a system where the proportional counter has been replaced with a silicon drift detector (SDD) to test milliprobing of mineral samples is described. In the region of the 14.4keV Mössbauer line the detector has about 70% efficiency and is capable of delivering spectroscopic information with...

Deep subduction and return to the surface of sediments and other continental rocks is now well known, forming terranes of ultrahigh-pressure metamorphism (UHPM). A common constituent of these terranes is garnet peridotite, mantle rock that has been brought to the surface along with the returning subducted material. Microstructures of these peridoti...

Ultra-High Pressure Metamorphism (UHPM) has its roots in the early 1960s discovery that glaucophane is stable only at high pressure and low temperature - implying that blueschists were carried to 10s of km rapidly and returned to the surface equally rapidly. Controversy erupted. Only with the advent of plate tectonics was the conceptual problem ove...