Terrestrial Rocks Research Articles

Fluorescent emission and nondestructive 3D textural imaging in geologic materials by multiphoton microscopy

This work greatly expands the application of multiphoton microscopy to geological investigations by using a tightly focused femtosecond laser beam to excite fluorescent emissions among minimally prepared rock and mineral samples. This novel finding provides a tool for spatially resolving UV-visible fluorescent sources in minerals. Through a combination of harmonic generation and fluorescence, unique opportunities are made available for mineralogical investigations of terrestrial rocks and astromaterials. This report includes the first demonstrations for 3D imaging of fluid inclusions in minerals and radiation-induced luminescence imaging in meteorites. Nonlinear optical mineralogy, enabled by multiphoton microscopy, provides unique insights into mineralogic samples and holds the potential to revolutionize the analysis of geologic and astromaterials samples in the coming years.

Composition and age constraints on a Hadean enriched mantle source revealed by the Paleoarchean São Tomé layered intrusion, NE Brazil

Evidence for Hadean depleted mantle reservoir(s) is well-established by mantle-derived rocks from multiple Archean complexes showing excesses in 142Nd compared to the modern mantle. Yet, the existence of an early enriched mantle source, which should have concomitantly formed during these Hadean silicate differentiation event(s), has only been recently confirmed by well-resolved 142Nd deficits measured in Paleoarchean mafic amphibolites from the São José do Campestre massif of the Borborema Province, NE Brazil. To investigate the nature and extent of this early-formed enriched reservoir, a series of samples from the Seridó belt, NE Brazil, have been investigated for their geochemical and coupled 147,146Sm-143,142Nd isotopic compositions, focusing on the Paleoarchean São Tomé layered intrusion. The São Tomé intrusion is composed of layers of metamorphosed mafic and ultramafic rocks with whole-rock trace element compositions and high olivine crystal Ni contents consistent with an incompatible trace element enriched pyroxenitic mantle source. Most analyzed samples from the Seridó belt yielded negative µ142Nd, as low as ∼ -20 (representing the lowest 142Nd/144Nd ratio ever measured in terrestrial rocks), with an average µ142Nd for the São Tomé intrusion of -9.6 ± 1.4. The São Tomé samples interpreted as the least isotopically disturbed yielded an 147Sm-143Nd isochron age of 3551 ± 368 Ma, consistent with previous zircon U-Pb ages, with an initial ε143Nd = -1.7 ± 1.2. Coupling the long-lived 147Sm-143Nd and the short-lived 146Sm-142Nd systems for the São Tomé rocks suggests a Hadean enriched mantle source formed at ∼4.44 Ga with a 147Sm/144Nd of ∼0.18, which may be complementary to the early depleted mantle recorded by Eoarchean rocks from the North Atlantic Craton, possibly formed during magma ocean crystallization. These results also imply that the record of this Hadean enriched mantle source is not restricted to the São José do Campestre massif but extends to a larger portion of the Borborema Province.

Insights from tensile fracture properties and full-field strain evolution of deep coral reef limestone under dynamic loads

Coral reef limestone (CRL) commonly undergoes dynamic tension when underground structures of island reefs encounter impacts, explosions, or seismic activities. Given the complexity of biological pores, the dynamic tensile fracture characteristics of CRL are poorly understood. Therefore, the dynamic tensile fracture behaviors of deep CRL were systematically observed by Split Hopkinson Pressure Bar tests and digital image techniques. Comparing to traditional rocks, the macro-pores near failure band would significantly change cracking path. The failure patterns are dominated by loading rate. The strongly dependence of dynamic tensile strength and dynamic crack initiation toughness on loading rate suggests the two indices overcome the effect of CRL macro-pores under dynamic impacts. At low loading rates, tensile fractures predominantly follow intergranular cracks, whereas transgranular cracks dominate at higher rates. The fractal dimension of fracture surface decreases with increasing crack propagation velocity, loading rate, and dynamic crack initiation toughness. Due to the unique marine sedimentary environment, the mechanical heterogeneity in multiple scales distinguishes CRL from terrestrial rock materials. The insights into underlying mechanisms of dynamic tension provide support to optimization of blasting scheme and stability assessments for island underground engineering.

Mine waste rock as a soil amendment for enhanced weathering, ecosystem services, and bioenergy production

Enhanced weathering of terrestrial rock material is a promising method for the removal of anthropogenic CO2 emissions from the atmosphere. Herein, we demonstrate that an ameliorated mining waste product can be effectively weathered in the soil environment when used as a soil amendment in conjunction with the cultivation of fast-growing willows (Salix matsudana Koidz. ⨯ S. alba L. “Austree”) in a pot study environment. Utilizing this locally sourced amendment minimizes emissions associated with grinding and transportation of enhanced weathering materials. Results showed that the willows were able to tolerate the relatively high metal concentrations of this amendment and sequester inorganic carbon (C) through the production of bicarbonate in soil solution. During the period of peak plant growth (10 weeks after planting), alkalinity measurements of soil solution from pots with willows and the addition of 25% by mass mine waste product indicated an additional 10 mg of inorganic C sequestration per liter of leached soil solution compared to unamended soils with willows. This represents 4.5 times the inorganic C sequestration rate of unamended soils. The addition of ameliorated mining waste also increased the pH of the soil solution by up to two units (pH of 6 in control vs. pH of 8 with the addition of 25% by mass mineral amendment). In addition to inorganic C sequestration, weathering of the ameliorated mining waste product may also provide base cations (such as calcium and magnesium) which could improve soil fertility. These results are encouraging for future investigation of ameliorated mine waste rock to sequester carbon and enhance the production of willows grown for ecosystem services and phytotechnologies.

Impactor identification with spallogenic Cr isotopes: The Wabar impact craters (Saudi Arabia)

AbstractPrecise measurements of Cr isotopic composition of terrestrial impactites have successfully provided evidence for the presence of extraterrestrial material and have, in some cases, allowed the identification of the type of impactor responsible for the formation of the impact structure. The high Cr abundance in most meteorite groups aids in detecting extraterrestrial contamination while their distinct isotopic compositions can help with the identification of the nature of the projectile. However, this common approach of detection and identification of extraterrestrial contamination using mass‐independent 53Cr and 54Cr variations fails when the impactor type is an iron meteorite because of their low Cr abundances (which are in a similar range to terrestrial rocks). The present study demonstrates the viability of a spallogenic Cr contribution in iron meteorites (resulting from their long cosmic ray exposure times), which compensates for their low Cr abundances and facilitates the identification of iron‐meteoritic contamination in terrestrial impactites. Thus, it broadens the scope of impactors (and impactites) that can be investigated using mass‐independent Cr isotopes from solely chondrites and primitive achondrites to include iron meteorites. The Wabar impact craters are an optimal candidate for this study, characterized by low weathering, diverse impactites, partial meteorite survival, substantial impactor material contamination, and a felsic target lithology with low background Cr concentration. The Cr isotopic composition of the Wabar background sand, which represents the target lithology, is indistinguishable from the terrestrial Cr isotopic composition range, whereas the Wabar iron meteorites show coupled spallogenic excesses in ε53Cr and ε54Cr. The Cr isotopic compositions of Wabar impactites show resolved deviations from the terrestrial Cr isotopic composition, thereby indicating the presence of Wabar meteoritic contamination. Moreover, the study demonstrates that even an impactor with a non‐carbonaceous chondritic origin, such as a IIIAB iron meteorite, can have a carbonaceous chondrite‐like signature in ε54Cr anomalies due to spallogenic Cr contamination. The study advocates for a comprehensive investigation combining platinum group elements and Cr (and/or Ni, Ru) isotopes to accurately characterize impactor types.

Volatile systematics in terrestrial igneous apatite: from microanalysis to decoding magmatic processes

Apatite has been recognized as a robust tool for the study of magmatic volatiles in terrestrial and extraterrestrial systems due to its ability to incorporate various volatile components and its common occurrence in igneous rocks. Most previous studies have utilized apatite to study individual magmatic systems or regions. However, volatile systematics in terrestrial magmatic apatite formed under different geological environments has been poorly understood. In this study, we filtered a large compilation of data for apatite in terrestrial igneous rocks (n > 20,000), categorized the data according to tectonic settings, rock types, and bulk-rock compositions, and conducted statistical analyses of the F–Cl–OH–S–CO2 contents (~ 11,000 data for halogen and less for other volatiles). We find that apatite from volcanic arcs preserves a high Cl signature in comparison to other tectonic settings and the median Cl contents differ between arcs. Apatite in various types and compositions of igneous rocks shows overlapping F–Cl–OH compositions and features in some rock groups. Specifically, apatite in kimberlite is characterized as Cl-poor, whereas apatite in plutonic rocks can contain higher F and lower Cl contents than the volcanic counterparts. Calculation using existing partitioning models indicates that apatite with a high OH (or F) content does not necessarily indicate a H2O-rich (or H2O-poor) liquid because it could be a result of high (or low) magma temperature. Our work may provide a new perspective on the use of apatite to investigate volatile behavior in magma genesis and evolution across tectonic settings, volatile recycling at subduction zones, and the volcanic-plutonic connection.

Comparative Study SVM and Random Forest Algorithms for the Classification of Terrestrial Visual Rock Types

Abstract The advancement in image processing technology, along with the increasing demand for classifying terrestrial visual rock types in diverse applications such as geological exploration and natural resource mapping, has prompted investigations into the application of machine learning algorithms to enhance classification accuracy. This research aims to assess the performance of the Support Vector Machine (SVM) and Random Forest algorithms in classifying terrestrial visual rock types. The study utilizes a dataset containing images of various rock types sourced from KAGGLE. Both Random Forest and Support Vector Machine methods are employed for rock type classification, and their performances are compared to determine the more effective method. Through experimental analysis on the KAGGLE rock dataset, the study provides evidence supporting the efficacy of the proposed method and identifies the Random Forest algorithm as the more suitable option for rock type classification. Evaluation criteria include accuracy, precision, recall, and F1-score metrics. The research findings reveal that the Random Forest algorithm achieves a higher accuracy rate of 86.25%, with a precision of 0.97, recall of 0.86, and an F1-Score of 0.91, establishing its superiority in rock type classification.

In situ investigation of the atomic structure of carbonate-silicate liquids at high pressure-temperature and spectroscopic characterization of the recovered quenched glasses

Carbonate-silicate melts that originate in Earth's interior are described as transitional melts which possess compositions intermediate between carbonatitic and basaltic end members. The covariation of key oxides between carbonatite and basalt (e.g., 10–35 wt% SiO2 and 40–10 wt% CO2, respectively) is expected to have a strong effect on liquid properties. However, due to their paucity both in the record of terrestrial rocks and as quenched glasses, their molecular structure has remained poorly explored to date. We investigated the atomic structure of a synthetic carbonate-silicate liquid with chemical composition within the CaO-MgO-Al2O3-SiO2-FeO-Na2O-ClO−-CO2 oxide system having 18.28 wt% SiO2 and 22.54 wt% CO2 using multi-angle energy dispersive X-ray diffraction at pressures (P) and temperatures (T) of 1.4 GPa/1815 °C, 2.6 GPa/1865 °C, 4.3 GPa/1990 °C, 4.4 GPa/1950 °C. The results show that the intermediate range ordering of the structure decreases with an increase of both P and T. Based on this study, the carbonate-silicate magmas at upper mantle P-T conditions are expected to increase their viscosities during their ascent through the mantle as a result of increasing intermediate range ordering upon cooling and decompression. Additionally, spectroscopic measurements were carried out on the quenched glasses at ambient pressure using micro-Raman as well as micro-FTIR in reflection and transmission modes in the mid infrared range. High pressure investigation using micro-FTIR was also conducted. The distribution of Qn species obtained by deconvolution of the Raman spectra within the aluminosilicate region confirms the depolymerized nature of the quenched glasses as inferred by the low viscosities of the corresponding liquids; peculiar characteristics of the C vibrations would suggest a distorted environment surrounding the network modifying CO32− anion. No evidence of molecular CO2 was detected. Notably, we find evidence of both dissolved molecular CO and CO linked to a metal cation forming carbonyl complexes in the quenched glasses at P-T-fo2 conditions compatible with a hot Archean upper mantle. This suggests a role for carbonate-silicate magmas as carriers of reduced gaseous C-O-H species towards the early atmosphere along with the mobilization of PGE-elements.

Planetary Paleomagnetic Intensity Recording Fidelity Test Using a Synthetic Lava

AbstractMeteorite paleomagnetism is fundamental to understanding planetary dynamo processes and the evolution of the early Solar System. However, due to the extraterrestrial and ancient origins of meteorites, their paleomagnetic recording fidelity remains uncertain, which can be tested from a planetary sample formed in a known field. On Earth, historic lavas are used to examine paleomagnetic recording fidelity through the Thellier‐series experiment and other paleointensity methods, which can produce paleointensity estimates to test against the known field strength. But natural terrestrial rocks have different magnetic mineralogy from planetary samples, so they cannot faithfully infer the recording fidelity of meteorites. Here, we used an iron‐particle‐bearing sample from the Syracuse University Lava Project (SULP), which is analogous to the lunar basalts and howardite‐eucrite‐diogenite meteorites and forms in the present‐day Earth's field, to investigate the recording fidelity of these meteorites. No remanence has been identified in the high coercivity range with alternating field (AF) demagnetization due to the sample's low coercivity and AF noise, which produces underestimated paleointensities. Two accurate thermal paleointensities indicate that we may acquire accurate paleointensities from non‐ideal multidomain (MD) iron grains with the Thellier‐Coe and RESET methods, but the success rate is low due to the MD effect and thermal alteration in the experiments. Our results imply that MD iron‐bearing meteorites have the potential to provide accurate paleointensities that can be used to constrain planetary processes.

Difference of hydrocarbon generation between argillaceous dolomite and mudstone and its influence on oil source: A case study of the Es4 in the Leijia area, Liaohe depression

Argillaceous dolomite and mudstone are two terrestrial source rocks that commonly occur together, and the difference in hydrocarbon generation characteristics determines the oil accumulation mode. The fourth member of the Shahejie Formation (Es4) in the Leijia area was used as an example to study the hydrocarbon generation characteristics and the overpressure difference caused by oil generation between argillaceous dolomite and mudstone, using hydrocarbon generation kinetics. Furthermore, the source of oil in the argillaceous dolomite reservoir was analyzed by combining the biomarker characteristics. The results indicated that the hydrocarbon generation characteristics of argillaceous dolomite and mudstone are significantly different. Mudstone starts hydrocarbon generation later and has a shorter hydrocarbon generation cycle, while argillaceous dolomite starts hydrocarbon generation earlier and has a longer hydrocarbon generation period. Due to the difference in hydrocarbon generation characteristics, when the burial depth is below 3000 m (EasyRo <0.85%), the oil-generation overpressure in the mudstone is smaller than that in argillaceous dolomite, and the tight oil in the argillaceous dolomite reservoir is mainly generated by and stored in the argillaceous dolomite itself. However, when the burial depth exceeds 3000 m (EasyRo >0.85%), the oil-generation overpressure in the mudstone surpasses that in argillaceous dolomite, and the tight oil has mixed source characteristics. The biomarker characteristics observed in extracts and crude oil confirm the above view. Whether tight oil exploration in argillaceous dolomite reservoir requires attention to the hydrocarbon supply capacity of adjacent mudstone depends on the maturity of organic matter.

Late Mesozoic–Cenozoic geoheritage resources of the Kharga Oasis (Egypt): Novel assessment, exploitation perspectives, and policy implications

Geoheritage resources are valuable to countries and regions, which make urgent their exploration. Particularly, Egyptian geoheritage has been examined only partly, and it has not been reported from many areas. New field investigations in the Kharga Oasis in the southern Western Desert of Egypt permit to report a new portion of geoheritage resources. The collected materials are used to propose six geosites, describe them (particularly, standardized geoheritage types are established), and assess semi-quantitatively. The approach is the same as already used for some other areas of Egypt, and the semi-quantitative assessment is based on scoring of various geosite properties with the different weight. It is established that these geosites exhibit lithologies and depositional environments of Upper Cretaceous–Eocene terrestrial and marine sedimentary rocks, Quaternary terrestrial carbonates (tufa deposits), and residual desert landforms. The geosites are attributed to the sedimentary, palaeogeographical, stratigraphical, palaeontological, and geomorphological geoheritage types. Scoring them by several criteria implies that two geosites (Naqb El-Rufuf and Naqb Bulaq) are national and four geosites (Naqb Assiut, Wadi El-Midawara, Gebel Taref, and Kharga Stadium) are regional in rank. The accessibility of some geosites is limited, and the Kharga Stadium geosite demonstrates significant vulnerability due to its location in the urban area. Generally, the analyses imply the presence of a valuable geoheritage resource in the Kharga Oasis. The outcomes of the present study also indicate the perspectives of scientific, educational, and touristic exploitation of the established geoheritage resources and the need in the development of the optimal policy for their effective management. Geopark creation seems to be a plausible instrument for the implementation of this policy, and its proposal requires further investigations of geological and cultural heritage of the Kharga Oasis.

Identification of atmospheric ozone generated from seismic activity during the occurrence of multiple earthquakes across Japan in 2022

Ground-level atmospheric ozone (tropospheric ozone) is a well-known indicator of photochemical air pollution. Atmospheric ozone may also be an indicator of earthquake generation. Ground-level observations of atmospheric ozone at multiple sites were conducted in this study at the time of multiple earthquake occurrences in Japan in 2022. As the result of this study, ozone peaks of unknown origin were detected during the occurrence of multiple earthquakes across Japan in 2022. The level of these ozone peaks began to increase from a few days to a few hours before each earthquake, reaching a maximum concentration coincident with the time of earthquake generation. ‘Unknown ozone’ were detected at near earthquake epicentres, except in the case of deep earthquakes. The ‘unknown ozone’ were also associated with earthquake seismic intensities, which were monitored at seismograph stations in various Japanese cities, towns, and villages. A laboratory experiment by Baragiola et al. (2011) indicated that ppm levels of ozone can be generated in air by the crushing and grinding of terrestrial crustal rocks, generated by exo-electrons emitted by high electric fields, resulting from charge separation during rock fracture. Baragiola et al. (2011) proposed a hypothesis whereby atmospheric ozone could be generated via rock fracturing during the occurrence of earthquakes. This hypothesis could explain the ozone peaks correlating with multiple Japanese earthquakes observed in this study. The significance of atmospheric ozone generated by seismic activity is discussed in terms of it being a possible indicator of earthquake generation and prediction.

Continental subduction in Paleoproterozoic: Insights from ∼ 1.9 Ga nepheline syenite in the North China craton

Subduction of continent is known as a feature of modern plate tectonics, and it is still unclear whether such a process also occurred in the early Precambrian. Despite of ultra-high pressure metamorphism of terrestrial rocks as a proxy of continental subduction, magmatism produced during continental subduction is also a potential alternative. The North China craton is well-known for the occurrence of 1.9 Ga retrograde eclogite, which was likely originated from the subducting oceanic crust along the Trans-North China Orogen (TNCO). Here a nepheline syenite (the Aohu pluton), the first of the kind from the TNCO, is discovered in Yunzhong Mts. It comprises nepheline (∼20 vol%), albite (50–55 vol%), K-feldspar (5–10 vol%), biotite (∼10 vol%), and calcite (∼5 vol%), with minor accessory minerals. No associated mafic or silicic rocks are outcropped in the pluton. SHRIMP zircon U-Pb analyses yield a crystallization age of 1893 ± 13 Ma and a metamorphic overprinting of 1871 ± 17 Ma. The rocks have medium SiO2 contents (51.9–58.9 wt%), low MgO (0.6–1.6 wt%) and Mg# (24–34), but high Al2O3 (20.0–22.9 wt%) and extremely high K2O + Na2O contents (10.0–13.6 wt%; Na2O/K2O = 1.3–2.6). They are enriched in light rare earth elements (REEs) and large ion lithophile elements, but relatively depleted in heavy REEs and high field strengthen elements. They have extremely low compatible elements (e.g., Ni and Cr). They show high (87Sr/86Sr)i ratios (0.706–0.707) but low εNd(t) values (−5.3 to −6.0; Nd T2DM = ca. 2.7 Ga). Their zircon in-situ εHf(t) values have a wide range (0 to −5.7; Hf T2DM = 2.5–2.85 Ga). The absence of mafic component and the extremely low-Mg feature, as well as their trace element patterns and initial Sr-Nd isotopes being compatible with melts derived from the Archean mafic crustal enclaves in the region, support a continental crust origin for the Aohu nepheline syenite. Based on comparison and modeling, we suggest that its generation was most likely under ultra-high pressure condition. It is thus proposed that continental subduction (into the mantle) might have occurred in the TNCO during the Paleoproterozoic.

Subtropical coastal microbiome variations due to massive river runoff after a cyclonic event

BackgroundCoastal ecosystem variability at tropical latitudes is dependent on climatic conditions. During the wet, rainy season, extreme climatic events such as cyclones, precipitation, and winds can be intense over a short period and may have a significant impact on the entire land‒sea continuum. This study focused on the effect of river runoff across the southwest coral lagoon ecosystem of Grand Terre Island of New Caledonia (South Pacific) after a cyclonic event, which is considered a pulse disturbance at our study site. The variability of coastal microbiomes, studied by the metabarcoding of V4 18S (protists) and V4–V5 16S (bacteria) rDNA genes, after the cyclone passage was associated with key environmental parameters describing the runoff impact (salinity, organic matter proxies, terrestrial rock origin metals) and compared to community structures observed during the dry season.ResultsMicrobiome biodiversity patterns of the dry season were destructured because of the runoff impact, and land-origin taxa were observed in the coastal areas. After the rainy event, different daily community dynamics were observed locally, with specific microbial taxa explaining these variabilities. Plume dispersal modeling revealed the extent of low salinity areas up to the coral reef area (16 km offshore), but a rapid (< 6 days) recovery to typical steady conditions of the lagoon's hydrology was observed. Conversely, during the same time, some biological components (microbial communities, Chl a) and biogeochemical components (particulate nickel, terrigenous organic matter) of the ecosystem did not recover to values observed during the dry season conditions.ConclusionThe ecosystem resilience of subtropical ecosystems must be evaluated from a multidisciplinary, holistic perspective and over the long term. This allows evaluating the risk associated with a potential continued and long-term disequilibrium of the ecosystem, triggered by the change in the frequency and intensity of extreme climatic events in the era of planetary climatic changes.

Not Only Garnets…

Abstract Garnets have been known to man since time immemorial and are used in a wide variety of applications as well as being prototypes of useful synthetic materials. Our investigations show that in nature, garnets and minerals with a langasite-type structure can be very close in composition. Examples are cubic Ti-rich garnets with the common formula Ca3(Ti4+,Fe3+,Al)2(Si,Fe3+,Al)3O12 and the new trigonal mineral qeltite, Ca3Ti(Fe3+2Si)Si2O14, which occur in paralavas of the pyrometamorphic Hatrurim Complex, Israel. Synthetic compounds of the langasite family are important because of their functional properties, such as unique piezoelectricity, high thermal stability, and low acoustic losses, as well as optical nonlinearity and multiferroicity. Qeltite is the first high-temperature terrestrial mineral with a langasite-type structure, the description of which was a catalyst for the discovery in pyrometamorphic rocks of the Hatrurim Complex of a whole series of new natural phases with langasite-type structure and varied composition (A3BC3D2O14, where A = Ca and Ba; B = Ti, Nb, Sb, and Zr; C = Ti, Al, Fe, and Si; and D = Si). We think that qeltite and other minerals with langasite-type structure may be relatively widely distributed in terrestrial rocks that form under similar conditions to those of Ti-rich garnet but are missed by researchers.

Nickel isotope fractionation factors between silicate minerals and melt

Quantitative knowledge of inter-mineral and mineral–melt isotopic fractionation factors is of crucial importance to interpret variability of mass-dependent isotope ratios in terrestrial rocks and meteorites. The isotopic composition of Ni shows great promise as a tracer of planetary differentiation, but the lack of solid constraints on the sign and magnitude of equilibrium Ni isotope fractionation factors hampers its further development. We address this issue by studying Ni isotope fractionation between silicate minerals and melt using a combination of carefully selected natural samples and olivine crystallisation experiments.Mineral separates from xenoliths are used to determine the Ni isotope fractionation behaviour of pyroxenes, spinel, and garnet relative to olivine. Nickel isotope fractionation between olivine and orthopyroxene is negligible, whereas clinopyroxene shows large variability that does not reflect equilibrium. Spinel has a clear affinity for the heavier isotopes of Ni relative to olivine; garnet has the lightest Ni isotope composition at equilibrium. The key parameter that dictates the sign and magnitude of Ni isotope fractionation during partial melting and crystallisation, however, is the olivine–melt fractionation factor. We present data for a natural basalt that contains olivine phenocrysts in chemical equilibrium with the host glass, and furthermore employ olivine crystallisation experiments in a 1-atmopshere furnace. Although the experiments invariably suffer from Ni loss to the Pt wire used to suspend the experiments in the furnace, these effects were carefully considered and quantified. The experiments limit the olivine–melt Ni isotope fractionation factor to lie between zero and slightly negative, which agrees very well with the natural datum, and we derive a best estimate value for Δ60/58NiOl–melt of −0.142 ± 0.031 ‰ at 1000 K. Hence, olivine has a subtle but clearly resolvable affinity for the lighter isotopes of Ni relative to basaltic melt. The implication is that equilibrium partial melts of mantle peridotite should have a slightly heavier Ni isotope composition than their source. Available Ni isotope data for mid-ocean ridge basalts show some overlap with modelled partial melts but extend to notably lighter Ni isotope compositions, potentially reflecting source heterogeneity or diffusive fractionation during melt transport.

Determination of Rare Earth Element Isotopic Compositions Using Sample-Standard Bracketing and Double-Spike Approaches.

Rare earth elements (REEs) have been found to have numerous uses to trace geological and cosmochemical processes through analyses of elemental patterns, radioactive decay, nucleosynthetic anomalies, and cosmogenic effects. Stable isotopic fractionation is one aspect of REE geochemistry that has been seldom studied, with most publications focusing on the development of analytical methodologies for individual REEs, and most applications concerning terrestrial igneous rocks. In this study, we present a method to systematically analyze stable isotopic fractionations of 8 REEs, including Ce, Nd, Sm, Eu, Gd, Dy, Er, and Yb, using sample-standard bracketing (SSB) and double-spike (DS) approaches. All REEs are separated and purified using a fluoropolymer pneumatic liquid chromatography (FPLC) system. We introduce procedures for identifying and correcting some isobaric interferences in double-spike data reduction. Several geostandards, including igneous rocks and sediments, are analyzed using SSB and DS methods. The results indicate that REE isotopic fractionation in igneous processes is limited, except for Eu. Other REEs can still be isotopically fractionated by low-temperature processes and kinetic effects at a high temperature.

Half-life of the nuclear cosmochronometer 176Lu measured with a windowless 4π solid angle scintillation detector

The 176Lu-176Hf nuclear decay is a powerful tool to measure the age of astrophysical and geological events and has been used as a “cosmochronometer”. However, the half-life values of 176Lu measured with various experiments differ significantly. Furthermore, the half-life values evaluated from Lu-Hf isochrons in meteorites and terrestrial rocks with known ages show two different values. Here we report half-life measurements using a method that is almost independent of various uncertainties. To the best of our knowledge this is the most accurate value of 176Lu half-life. We measure the total energy released from 176Lu decay using a windowless 4π solid angle detector based upon bismuth germanate (BGO) scintillation crystals, where a natural Lu sample is located inside of the detector. The measured half-life of (3.719 ± 0.007) × 1010 yr corresponding to a decay constant of (1.864 ± 0.003) × 10−11 yr−1 is consistent with that obtained from the analysis of terrestrial rocks within the uncertainty.

The Potwar Siwaliks: an impressive Neogene record of terrestrial rocks and fossils

Abstract Outcropping sedimentary deposits of the Potwar Plateau in northern Pakistan comprise the most complete record of Neogene Siwalik rocks and faunas to be found in the Indian subcontinent documenting an extraordinary record of terrestrial vertebrate fossils for the Miocene Epoch. The Potwar Plateau is a portion of the Siwalik Hills, the mountainous terrane of the outer Himalayas extending over 2000 km across the northern margin of the Indian subcontinent. Siwalik strata accumulated as a molassic sedimentary wedge shed southward with the erosion of the rising crust as it was uplifted via plate tectonics. The long Potwar record of numerous superposed assemblages of fossil vertebrates preserves a history spanning many millions of years, and constitutes a unique geoheritage resource for Asia and for the world. The record can be dated and interpreted with a high degree of precision rarely achieved in terrestrial settings. The Potwar Siwalik sediments document 18 million years of change in the subtropical ecosystem of South Asia, in which global to regional climate change directly impacted terrestrial palaeofloras and palaeofaunas, forcing coevolution of elements of the terrestrial food web, and with that the modernization of mammalian groups. The potential to trace coincidence of abiotic changes with evolution within lineages is unusual.

Distribution and geochemical significance of alkylbenzenes for crude oil with different depositional environments and thermal maturities

A total of 45 alkylbenzenes were detected and identified in crude oils with different depositional environments and thermal maturities from the Tarim Basin, Beibuwan Basin, and Songliao Basin using comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC × GC-TOFMS). By analyzing the distribution characteristics of C0–C5 alkylbenzenes, it is found that the content of some alkylbenzenes varies greatly in crude oils. Based on the distribution characteristics of 1,2,4,5-tetramethylbenzene (TeMB) and 1,2,3,4-TeMB, the ratio of 1,2,4,5-TeMB to 1,2,3,4-TeMB is proposed to indicate the organic matter origin and depositional environment of ancient sediments. Oil samples originated mainly from lower hydrobiont, algae, bacteria and source rocks deposited under reducing/anoxic conditions have low 1,2,4,5-/1,2,3,4-TeMB values (less than 0.6), while oil samples originated mainly from terrestrial higher plants and source rocks deposited under oxic/sub-oxic conditions have higher 1,2,4,5-/1,2,3,4-TeMB values (greater than 1.0). The significant difference of 1,2,4,5-/1,2,3,4-TeMB values is controlled by 1,2,4,5-TeMB content. 1,2,4,5-TeMB content in oils derived from source rocks deposited in oxidized sedimentary environment (greater than 1.0 mg/g whole oil) is higher than that in oils from source rocks deposited in reduced sedimentary environment (less than 1.0 mg/g whole oil). 1,2,4,5-/1,2,3,4-TeMB ratio might not or slightly be affected by evaporative fractionation, biodegradation and thermal maturity. 1,2,4,5-/1,2,3,4-TeMB ratio and 1,2,4,5-TeMB content can be used as supplementary parameter for the identification of sedimentary environment and organic matter input. It should be noted that compared to the identification of organic matter sources, the 1,2,4,5-/1,2,3,4-TeMB parameter is more effective in identifying sedimentary environments.