Petrology
Petrology is a peer-reviewed journal devoted to magmatic, metamorphic, and experimental petrology, mineralogy, and geochemistry. The journal offers comprehensive information on all multidisciplinary aspects of theoretical, experimental, and applied petrology. By giving special consideration to studies on the petrography of different regions, the journal provides readers with a unique opportunity to refine their understanding of the geology of the vast territory of the Eurasian continent. Previously focused on translation, the journal now has the aim to become an international publication and accepts manuscripts originally submitted in English from all countries, along with translated works.
Peer review and editorial policy
The journal follows the Springer Nature Peer Review Policy, Process and Guidance, Springer Nature Journal Editors' Code of Conduct, and COPE's Ethical Guidelines for Peer-reviewers.
Approximately 20% of the manuscripts are rejected without review based on formal criteria as they do not comply with the submission guidelines. Each manuscript is assigned to two peer reviewers. The journal usually follows a single-blind review procedure, but open peer review is sometimes practiced. The period from submission to the first decision is up to 40 days. The approximate rejection rate is 30%. The final decision on the acceptance of a manuscript for publication is made by the Meeting of Editorial Board members or by the meeting of the most active members of the Editorial Board.
If Editors, including the Editor-in-Chief, publish in the journal, they do not participate in the decision-making process for manuscripts where they are listed as co-authors.
Special issues published in the journal follow the same procedures as all other issues. If not stated otherwise, special issues are prepared by the members of the editorial board without guest editors
Current Issue
Open Access
Access granted
Subscription Access
Vol 27, No 6 (2019)
- Year: 2019
- Articles: 6
- URL: https://journals.rcsi.science/0869-5911/issue/view/11003
Article
Experimental Study of the Peridotite–Basalt–Fluid System: Phase Relations at Subcritical and Supercritical Р-Т Conditions
Abstract
The paper reports experimental data on the partial melting of hydrous peridotite and basalt at pressures up to 4 GPa and temperatures up to 1400°С, as well as peridotite–basalt association in the presence of alkaline water–carbonate fluid as an experimental model of mantle reservoir with subducted oceanic protoliths. At partial melting of the hydrous peridotite at 3.7–4.0 GPa and 1000–1300°С, critical relations were observed over the entire studied pressure and temperature interval. At partial melting of hydrous basalt, critical relations between silicate melt and aqueous fluid were recorded at 1000°С and 3.7 GPa. The Na-alkaline silicate melt coexists with garnetite at 1100°С and with clinopyroxenite at 1150 and 1300°С. The peridotite–basalt–alkaline-aqueous–carbonate fluid at 4 GPa and 1400°C shows signs of critical relations between a carbonated silicate melt and a fluid. Reaction relations in the residual peridotite minerals with replacements of olivine ← orythopyroxene ← clinopyroxene ← potassic amphibole-type testify to a high chemical activity of the supercritical liquid. Experimental results suggest the existence of regions of partial melting (asthenospheric lenses) in the fluid-bearing upper mantle under supercritical conditions. These lenses contain near-solidus highly reactive supercritical liquids enriched in incompatible elements. Mantle reservoirs with supercritical liquids are geochemically similar to undepleted mantle and could serve as sources of magmas enriched in incompatible elements. The modal and cryptic upper mantle metasomatism under the effect of supercritical liquids leads to the refertilization of peridotite via enrichment of residual minerals in incompatible elements.
553-566
Physical and Chemical Parameters of Processes Producing Rare-Metal Deposits in Granitoid Systems with Fluorine: Experimental Data
Abstract
The origin of rare-metal deposits in granites is considered with regard for experimental data, which place constraints onto interpretations of geological materials and the genetic models. The role of both magmatic and hydrothermal–metasomatic factors in the formation of various types of rare-metal deposits is discussed. The saturation concentrations of Ta and Nb in granite melt significantly depend on the melt composition and vary from ~2–5 to ~0.1 wt %. These concentrations depend much less significantly on temperature and pressure. In granite melt in equilibrium with fluorine-bearing fluid, Ta and Nb are strongly partitioned into the melt. The paper demonstrates principal difference in the partitioning of W and Ta, Nb, Sn in melt granite–salt systems. The fluoride water–salt phase is a very effective extractant of W, while Ta, Nb, and Sn are completely retained in the aluminosilicate melt. The model magmatic fluid in equilibrium with Li–F granite melt is multiphase and contains significant amounts of SiO2 and Na, Al, Li and K fluorides. The solubility of ore minerals in this fluid is insignificant, with the concentration of Nb much higher than that of Ta. The HF concentrations in high-temperature magmatic fluids were estimated at ~0.5–1 M HF. The experimentally determined solidus temperatures of Li–F granites are ~570–630°C at a pressure of 100–200 MPa. At T = 300–550°С and P = 50–100 MPa, the actual hydrothermal transfer of Ta and Nb is possible only with sufficiently concentrated HF and, possibly, KF solutions (fluids). In sodium alkaline solutions, hydrothermal transport is quite probable for Nb but difficult for Ta, and the pyrochlore solubility is thereby higher than that of columbite.
567-584
Partitioning of Volatile Components (Cl, F, and CO2) in Water-Saturated Fluid–Magma Systems of Various Composition
Abstract
The paper presents results of experimental studies of the behavior of volatile components (Cl, F, CO2, and H2O) in fluid–magmatic systems. The maximum Cl content in magmatic melts depends mainly on the composition of the melt and less on pressure (10–300 MPa) and temperature (800–1000°C). The Cl content in the melt increases from 0.2–0.3 to 3–5 wt % with increasing Ca content during the transition from polymerized granitoid to depolymerized basaltic melts. The pressure dependence of the solubility has a maximum at a pressure of about 100–200 MPa. The Cl and F contents in the melt tend to increase and decrease, respectively, at the transition from acid and alkaline to basalt melts. The maximum Cl content in the melt significantly increases from rhyolite (no more than 0.25 wt %) to phonolite (no more than 0.85 wt %), and dacite (no more than 1.2 wt %) melts at temperatures of 1000–1200°C and a pressure of 200 MPa. The addition of CO2 to the system leads to an increase in the Cl content in the melt by 20–25 relative %, which is likely explained by an increase in Cl activity in the fluid. Thereby the H2O content in the melt decreases by ~0.5–1.0 wt %. Hydrolysis is demonstrated to strongly affect interaction between alumina-rich granitic melt and ~0.5–1 N chloride fluid. This effect shows that the fluid is acidic (pH after the experiment is ~1–1.5) at hypabyssal magmatic conditions (P = 100 MPa, T = 750°C) and is characterized by a high dissolving power. The experiments show that interaction between aqueous Na–K–Ca–chloride fluid of variable composition and granodioritic and granitic melts in the pressure range of ~100–200 MPa, temperatures of 820–1000°C, and an increasing total salt content leads to that Na and K substitute Ca in the silicate melt, with Ca simultaneously passing into the fluid. The latter is enriched in CaCl2 and is depleted in NaCl. Experimental results on the coupled Cl and F partitioning provide a quantitative basis for understanding degassing processes in the course of the evolution of alkaline and basaltic magmas. They are important for assessing the extent of Cl and F removal into the Earth’s atmosphere during volcanic activity and the effects of this removal on climate changes.
585-605
Petrological-Geochemical Characteristics of Lavas, Sources and Evolution of Magmatic Melts of the Kazbek Neovolcanic Center (Greater Caucasus)
Abstract
The results of petrological-geochemical and isotope-geochemical studies of the Late Pleistocene-Holocene lavas of the Kazbek neovolcanic center, one of the largest centers of youngest magmatism in the Greater Caucasus, are presented. It has been established that the volcanic rocks of the Kazbek center form a continuous compositional series basaltic (trachy-)andesites–(trachy-)andesites–dacites with a predominance of calc-alkaline intermediate and moderately-acid lavas. The obtained results indicate that fractional crystallization and mixing of melts had a leading role in the petrogenesis of the rocks. The crustal assimilation was of limited importance; its influence is noticeable only in the rocks of the earliest and late pulses of magmatic activity within the Kazbek center. The common crustal lithologies participating in the assimilation were metamorphosed Jurassic sediments (mainly shales and sandstones) forming the base of the Kazbek center and rarely Mesozoic mafic metamorphosed volcanites. The specific features of AFC processes during the development of the studied magmatic system (including the presence of noticeable amount of water in the melt, the leading role of Amp in the cumulus and the absence of Pl fractionation) led to the appearance of dacitic lavas with geochemical signs of adakites as an evolutional end-member. The volcanic rocks of the Kazbek center are derived from trachybasalt magmas, the source of which was presented by the mantle reservoir of OIB-type. Recent and previously published results of studies of the Neogene-Quaternary magmatism manifested within the Greater Caucasus show that the main petrological and geochemical characteristics of this regional mantle reservoir remained constant from the end of the Miocene to the present time.
606-632
Genesis and Evolution of Mantle Melts of the Devonian Mafic-Ultramafic Rocks from the Eastern Azov Region (Dnieper-Donets Rift, Ukraine): Evidence from Clinopyroxene Geochemistry
Abstract
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
633-654
Geodynamic Nature of Magmatic Sources in the Northwest Pacific: An Interpretation of Data on the Sr and Nd Isotope Composition of Rocks Dredged at the Stalemate Ridge, Ingenstrem Depression, and Shirshov Rise
Abstract
The paper presents the first data on the Sr and Nd isotope composition of rocks from a unique collection of magmatic rocks of all petrographic types (basalts, gabbro, and peridotites) belonging to the lithosphere at the convergent plate boundary in the Aleutian Arc area. The rock samples were collected over large areas in the Northwest Pacific and Bering Sea. The results of this study provide reliable information on the geodynamic nature of the central segment of the Shirshov Rise, which is made up of magmatic rocks whose isotopic–geochemical features indicate that they were produced by magmatic melts that evolved within the crust and were derived by the partial melting of MORB parental source, which may have belonged to a mantle wedge. The isotopic–geochemical characteristics of the rocks at the Shirshov Rise suggest that the mafic–ultramafic rocks association may have been produced at a backarc spreading center. Petrological and isotopic–geochemical traits of rocks dredged at the northwestern flank of the Stalemate Ridge indicate that the sources of the parental melts were heterogeneous. Data on the rocks suggest that magmatism in this part of the Northwest Pacific may have involved a source responsible for the origin of the oldest seamounts in the Hawaiian–Emperor Volcanic Chain. Ultramafic rocks in the northwestern segment of the Stalemate Ridge show similarities with plutonic rocks found as xenoliths in volcanics of the Aleutian Island Arc. With regard for the scarcity of information on the structure of the lithosphere in this part of the Pacific, it can be cautiously suggested that the oceanic slope of the Aleutian Trench and adjacent segment of the Stalemate Ridge involve fragments of the basement of the Aleutian Island Arc.
655-674