Rb Depletion Research Articles

Rb-Sr isotope systematics of the oldest crustal rock in the solar system

The RbSr isotopic system is an important cosmochemical tool for constraining the evolution of moderately volatile (Rb) and refractory (Sr) elements in the earliest Solar System. Presented here are RbSr isotopic systematics of twenty-two fractions of the evolved achondrite Erg Chech 002, the oldest crustal rock yet identified in the Solar System. Although the data show a large amount of scatter, likely due to terrestrial alteration, an errorchron yields an age within uncertainties of published PbPb ages. Initial 87Sr/86Sr ratios of both the errorchron and of individual mineral fractions show that Erg Chech 002 formed from materials evolving with a typical CI-chondrite nebular Rb/Sr ratio and that any Rb depletion on its parent body must have occurred almost simultaneously with the crystallization of the meteorite. Additionally, LuHf systematics of bulk Erg Chech 002 overlap with the chondritic range. Other early-formed parent bodies similarly show initial 87Sr/86Sr ratios close to a CI-chondrite evolution line. Despite nucleosynthetic variations of 84Sr/86Sr being evident between inner and outer Solar System materials, no variations are detectable in 87Sr/86Sr for Erg Chech 002 or other early-formed parent bodies. Although the initial 87Sr/86Sr of Erg Chech 002 overlaps with that of all other early-accreted bodies, the initial 87Sr/86Sr of asteroid 4 Vesta (BABI) remains the most precise and relevant initial value for the bulk silicate Earth.

Geochronology and Geochemistry of Paleoproterozoic Mafic Rocks in Northern Liaoning and Their Geological Significance

Petrological, geochronological, and geochemical analyses of mafic rocks in northern Liaoning were conducted to constrain the formation age of the Proterozoic strata, and to further study the source characteristics, genesis, and tectonic setting. The mafic rocks in northern Liaoning primarily consist of basalt, diabase, gabbro, and amphibolite. Results of zircon U-Pb chronology reveal four stages of mafic magma activities in northern Liaoning: the first stage of basalt (2209 ± 12 Ma), the second stage of diabase (2154 ± 15 Ma), the third stage of gabbro (2063 ± 7 Ma), and the fourth stage of magmatic protolith of amphibolite (2018 ± 13 Ma). Combined with the unconformity overlying Neoproterozoic granite, the formation age of the Proterozoic strata in northern Liaoning was found to be Paleoproterozoic rather than Middle Neoproterozoic by the geochronology of these mafic rocks. A chronological framework of mafic magmatic activities in the eastern segment of the North China Craton (NCC) is proposed. The mafic rocks in northern Liaoning exhibit compositional ranges of 46.39–50.33 wt% for SiO2, 2.95–5.08 wt% for total alkalis (K2O + Na2O), 6.17–7.50 wt% for MgO, and 43.32–52.02 for the Mg number. TiO2 contents lie between 1.61 and 2.39 wt%, and those of MnO between 0.17 and 0.21 wt%. The first basalt and the fourth amphibolite show low total rare earth element contents. Normalized against primitive mantle, they are enriched in large ion lithophile elements (Rb, Ba, K), depleted in high field strength elements (Th, U, Nb, Ta, Zr, Ti), and exhibit negative anomalies in Sr and P, as well as slight positive anomalies in Zr and Hf. The second diabase and the third gabbro have similar average total rare earth element contents. The diabase shows slight negative Eu anomalies (Eu/Eu* = 0.72–0.88), enrichment in large ion lithophile elements (Ba), depletion in Rb, and slight positive anomalies in high field strength elements (Th, U, Nb, Ta, Zr, Hf, Ti), with negative anomalies in K, Sr, and P. The gabbro is enriched in large ion lithophile elements (Rb, Ba, K), depleted in high field strength elements (Th, U, Nb, Ta, Zr, Hf), and exhibits positive anomalies in Eu (Eu/Eu* = 1.31–1.37). The contents of Cr, Co, and Ni of these four stages of mafic rocks are higher than those of N-MORB. The characteristics of trace element ratios indicate that the mafic rocks belong to the calc-alkaline series and originate from the transitional mantle. During the process of magma ascent and emplacement, it is contaminated by continental crustal materials. There are residual hornblende and spinel in the magma source of the first basalt. The other three magma sources contain residual garnet and spinel. The third gabbro was formed in an island arc environment, and the other three stages of mafic rocks originated from the Dupal OIB and were formed in an oceanic island environment. The discovery of mafic rocks in northern Liaoning suggests that the Longgang Block underwent oceanic subduction and extinction in both the north and south in the Paleoproterozoic, indicating the possibility of being in two different tectonic domains.

Abstract 1648: RB represses cohesin-dependent loop formation and activates E2F-independent transcription

Abstract The retinoblastoma protein (RB) suppresses the activity of the E2F transcription factor family, controlling cellular proliferation. Recent studies, however, indicate that RB's role in chromatin organization, which is not yet fully understood, might be distinct from this E2F-dependent regulation. Employing chromosome conformation capture at a single nucleosome resolution, we identified RB as a cell cycle-regulated repressor of cohesin-dependent loop formation at topologically associating domain (TAD) boundaries. RB depletion increased the number and size of cohesin-dependent loops and strengthened topologically associating domains (TADs). This phenomenon was specific to the G1 phase and was not observed in the S phase, indicating that this novel RB function is regulated by the cell cycle. Mechanistically, RB showed extensive colocalization with cohesin in the human genome, and it impacted cohesin’s distribution on the chromatin. Active RB reduced cohesin from RB-bound TAD boundaries and decreased cohesin activity therein, as assessed by the increased K105/106 acetylation of the cohesin subunit SMC3. This led to reduced insulation in chromosome conformation capture assays. Importantly, by weakening the insulation activity of the adjacent insulators, RB non-canonically enhanced the expression of non-E2F target genes salient for cell adhesion and extracellular matrix organization. When RB was lost, cells showed a more rapid cellular detachment rate and an elevated migration rate, indicating that this novel RB function controls specific transcriptional programs rather than arbitrary genes to regulate the process of cell adhesion and migration. Overall, we conclude that RB has a central role in the interplay between cell cycle and chromatin organization, by repressing the cohesin-dependent loop formation at TAD boundaries. This RB function safeguards E2F-independent transcriptional programs driven by active enhancers and helps maintain cellular adhesion to the extracellular matrix. Citation Format: Hanjun Lee, Ioanna-Maria Gkotinakou, Badri Krishnan, Nicholas J. Dyson, Michael S. Lawrence, Ioannis Sanidas. RB represses cohesin-dependent loop formation and activates E2F-independent transcription [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1648.

Geochemistry of the North Gondwana Paleozoic Araba and Naqus formation siliciclastics, Sinai: implications for provenance, paleoweathering, and tectonic setting

ABSTRACT The Araba and Naqus formations in Ras Milan, Sinai, constitute part of the major continuous Paleozoic clastic belt stretching across northern Gondwana. They are sandstone-dominated successions, resting on Precambrian granitic basement, with lowermost thin basal polymictic conglomerate deposits (1–2 m), marking the unconformity. The Araba Formation section is composed mainly of varicoloured violet to reddish brown, fine to coarse-grained laminated and planner and overturned cross-bedded sandstones, while the overlying Naqus Formation is characterized by chaotically distributed poorly sorted quartz pebbles to cobbles within a moderately-sorted coarse- to medium-grained quartz arenite and by abundance and variety of large-scale tabular and trough cross bedding. Modal QFL classification of Araba and Naqus formation sandstones revealed that they are merely quartzose sandstones (quartz arenites). Geochemistry of the succession shows extremely wide compositional ranges for almost all major elements, but the Araba Formation is relatively enriched in SiO2, TiO2, Fe2O3*, Na2O, P2O5, and depleted in Al2O3, MgO, CaO and K2O relative to Naqus Formation. Only the Araba Formation samples are depleted in the transition elements Ni, Cr and Co and oppositely possess extreme enrichment in the HFSEs (i.e. Zr, Hf, Y, Nb, Ta, Th, U), whereas both formations show variable depletion in the LILE Rb, K and Ba, and excessive REE abundances relative to the PAAS and UCC, and LREE-enriched patterns with marked negative Eu anomalies. The provenance of the Naqus and Araba formations could be an earlier felsic magmatic source, which has undergone extensive sedimentary recycling. They possess high compositional maturity and were subjected to intensive to moderate weathering during humid climatic conditions. Passive margin tectonic setting is implied which denotes the derivation of Araba and Naqus formation siliciclastics from stable continental regions or plate interiors and deposition in intracratonic basins.

Abstract C062: Defining the interplay between PARP and the RB/E2F axis in prostate cancer

Abstract Prostate cancer (PCa) is the second leading cause of cancer-related death in American men. Non-Hispanic Black men are 1.8 times more likely to develop PCa and 2.3 times more likely to die from PCa. Tumor suppressor retinoblastoma (RB1) is frequently deleted in PCa. RB represses the transcriptional activity of E2Fs and the phosphorylation of RB by CDK4/6 results in dissociation of the complex and a subsequent increase in E2F transcriptional activity, leading to cell cycle progression. RB loss is associated with tumor aggressiveness occurring in 10-15% of castration-resistant prostate cancer (CRPC) tumors and corresponds to a decrease in overall survival. RB depletion leads to increased expression of DNA repair proteins due to elevated transcriptional activity of E2F1. PARP-1 is an enzyme that plays a role in DNA repair. Elevated PARP-1 enzymatic activity is associated with PCa progression and correlates with poor clinical outcomes in CRPC. E2F1 transcriptional activity is supported by PARP enzymatic activity, however the consequences of the functional interaction between the RB/E2F axis and PARP remains an open line of inquiry. Defining the interplay between PARP and RB/E2F is likely to contribute to the identification of novel treatment strategies and/or biomarker response. Canonically, E2F1-3 are transcription factors that positively regulate gene expression programs associated with pro-proliferative signals. Prior research by other groups has shown that E2F target genes expression is elevated in tumors excised from Black men compared to Asian and White men. There was an increase in germline RAD51 mutations observed. RAD51 is an E2F target gene involved in DDR, therefore attenuating PARP enzymatic activity may be a potential mode of targeting this axis. These data suggest that there may be differential DNA damage response (DDR) in African American men driven by aberrations in the RB/E2F signaling axis, however the mechanism is yet to be fully explored. Analysis of publicly available patient datasets were performed and demonstrate that RB1 deletions is more frequent than RB1/BRCA2 co-deletion in metastatic PCa. Isogenic models of RB1 knockdown were used to evaluate the impact of RB loss on PARP enzymatic activity. PARP-1 mRNA and PARP-1 protein are elevated upon RB1 depletion with a concomitant increase in PARP activity. Growth curve assays were conducted to examine the biological response to PARP inhibition in the isogenic models. In hormone-depleted conditions, results suggest a differential response between RB depleted models compared to the control when challenged with PARP inhibition. Furthermore, an IC50 dose of Olaparib elicits differential PARP enzymatic response in the RB1 depleted model. RB1 loss is associated with an enrichment in E2F1 binding at the PARP-1 locus. Future studies have been designed to determine the impact of the RB/E2F pathway alterations on downstream consequences PARP enzymatic function and establish the contribution of PARP and the RB/E2F axis on racial disparity in PCa. Citation Format: Latese Evans. Defining the interplay between PARP and the RB/E2F axis in prostate cancer [abstract]. In: Proceedings of the 16th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2023 Sep 29-Oct 2;Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(12 Suppl):Abstract nr C062.

The early Late Triassic Yumen mafic rocks in the eastern Tethyan Himalaya: A record of the progressive opening of the Yarlung Zangbo Neo-Tethyan Ocean

The timing of the opening of the Yarlung Zangbo Neo–Tethyan Ocean (YZNTO) is debated. In this contribution, geochemical and geochronological analyses of diabase, pillow basalt and layered basalt from the Upper Triassic Yumen tectonic mélange (T3Y) of the eastern Tethyan Himalaya in South Tibet are used to elucidate the timing and the magmatic evolution preceding the development of the YZNTO. Zircon U-Pb geochronology indicates that the Yumen mafic rocks crystallized in the Late Triassic (diabase, c. 225 Ma). These rocks display alkaline basalt affinities and have variable enrichment in Ba, U, Pb, Sr and Ti and depletion in Rb, Th and Nb. The diabase and pillow basalt samples have compositions transitional between enriched mid–ocean ridge basalt and ocean island basalt (OIB); layered basalt is more compatible with an OIB affinity. Whole–rock εNd (t) ratios of the mafic rocks range from +5.5 to +11.5 and zircons from a diabase have εHf(t) values varying from – 1.1 to +10.0. Whole–rock trace element concentrations indicate that the parental magmas of the Yumen mafic rocks were derived from the mantle at variable depths extending from the garnet to spinel stability fields. The Yumen mafic rocks originated from partial melting of a heterogeneous magma source composed of dominant depleted asthenospheric magmas and the addition of some components of an ancient and enriched lithospheric mantle; negligible crustal contamination occurred. Combined with previous studies, we conclude that the Yumen mafic rocks were probably produced in an intercontinental rift setting with extremely thin continental lithosphere in the early Late Triassic prior to the opening of the eastern YZNTO. The YZNTO progressively opened along the northern edge of the Indian plate from west to east in the Phanerozoic.

Abstract B063: Interplay between PARP and the RB/E2F axis in prostate cancer

Abstract Retinoblastoma (RB) protein is a tumor suppressor that represses the transcriptional activity of E2Fs by forming an RB-E2F repressor complex. The phosphorylation of RB by CDK4/6 results in dissociation of the complex and subsequent E2F transcriptional activity, leading to cell cycle progression. RB loss occurs in 10-15% of castration-resistant prostate cancer (CRPC) which is associated tumor aggressiveness and poor clinical outcomes. RB loss is also associated differential treatment response to an array of treatment modalities, including hormone therapy and DNA damage inducing chemotherapy. RB depletion leads to enhanced expression of DNA repair proteins due to increased transcriptional activity of E2F1. PARP-1 is an enzyme that plays a role in multiple nuclear processes including DNA repair, transcriptional regulation, and chromatin dynamics. Increased PARP-1 activity is associated with and correlates to poor clinical outcomes in CRPC. E2F1 transcriptional activity is supported by PARP enzymatic activity, but the consequences of the functional interaction between the RB/E2F axis and PARP remains an open line of inquiry, which may yield novel treatment strategies and/or biomarkers of response. Isogenic models of RB1 knockdown were used to evaluate the impact of RB loss on PARP enzymatic activity. PARP-1 protein increases upon RB1 depletion with a concomitant increase in PARP activity. Growth curve assays were conducted to examine the biological response to PARP inhibition in the isogenic models. Results suggest a differential response between control and RB1 depleted cells when treated with Olaparib. RB1depleted cells also exhibit differential PARP activity in response to treatment with the IC50 dose of Olaparib. Future studies have been designed to evaluate the impact of RB alteration and manipulation of PARP activity on biological and molecular processes that are governed by RB/E2F and PARP. Citation Format: Latese Evans, Moriah Cunningham, Jasibel Vasquez Gonzalez, Matthew Schiewer. Interplay between PARP and the RB/E2F axis in prostate cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr B063.

CDK4/6 inhibitors and the pRB-E2F1 axis suppress PVR and PD-L1 expression in triple-negative breast cancer

Immune-checkpoint (IC) modulators like the poliovirus receptor (PVR) and programmed death ligand 1 (PD-L1) attenuate innate and adaptive immune responses and are potential therapeutic targets for diverse malignancies, including triple-negative breast cancer (TNBC). The retinoblastoma tumor suppressor, pRB, controls cell growth through E2F1-3 transcription factors, and its inactivation drives metastatic cancer, yet its effect on IC modulators is contentious. Here, we show that RB-loss and high E2F1/E2F2 signatures correlate with expression of PVR, CD274 (PD-L1 gene) and other IC modulators and that pRB represses whereas RB depletion and E2F1 induce PVR and CD274 in TNBC cells. Accordingly, the CDK4/6 inhibitor, palbociclib, suppresses both PVR and PD-L1 expression. Palbociclib also counteracts the effect of CDK4 on SPOP, leading to its depletion, but the overall effect of palbociclib is a net reduction in PD-L1 level. Hydrochloric acid, commonly used to solubilize palbociclib, counteracts its effect and induces PD-L1 expression. Remarkably, lactic acid, a by-product of glycolysis, also induces PD-L1 as well as PVR. Our results suggest a model in which CDK4/6 regulates PD-L1 turnover by promoting its transcription via pRB-E2F1 and degradation via SPOP and that the CDK4/6-pRB-E2F pathway couples cell proliferation with the induction of multiple innate and adaptive immunomodulators, with direct implications for cancer progression, anti-CDK4/6- and IC-therapies.

The last Neoproterozoic rift magmatism on the western margin of Yangtze block, South China: New insights of Marinoan onset from low-δ18O magmatic events

The geological record preserves evidence of “Snowball Earth” glaciations during the Cryogenian Period, the Sturtian onset at ca. 720 Ma and the Marinoan onset at ca. 650 Ma. Compared to the Sturtian, the trigger for the Marinoan is still unclear due to the absence of large igneous provinces (LIPs). This study first discovered low-δ18O Luoluobuzi (LLBZ) granite which emplaced on the eve of the Marinoan at the Yangtze Block in South China. The granite with U-Pb age of 651.2 ± 2.1 Ma and has εHf (t) values between + 6.8 to + 13.3, and low-δ18O values between + 2.74 to + 5.34 ‰. Granite samples show Ba, Nb, Ta, Sr, Eu, and Ti depletion and enrichment in Rb, U, Th, and Pb, modeling calculations to suggest they originated from partial melting of nearby Neoproterozoic mafic rocks and formed in a continental rift. We systematically compiled data and found an interglacial period between the Sturtian-Marinoan glaciations is absent of magmatic activities. Extensional magmatic activity similar to the LLBZ granite started at ca. 651 Ma, which within errorsoverlapped the onset of the Marinoan. Such temporal ruling also existed in other worldwide rift-related magmatic activities. After combining chemical index of alteration (CIA) and palaeomagnetic results, we found the last episode of Rodinia breakup played an important role in the onset of the Marinoan.

Early Paleozoic oceanic slab subduction in South China: Evidence from adakite‐like granodiorite and high‐Mg diorite from Puyang pluton in the Wuyi orogenic belt

AbstractThe mechanism of Caledonian orogeny in South China is still controversial. The main argument focuses on the issue that whether there existed oceanic subduction. To answer this question, the complex Puyang pluton in the central part of Wuyi orogenic belt was selected for zircon U–Pb dating, in‐situ Lu–Hf isotopic analysis and geochemical testing. The Puyang pluton is mainly composed of granodiorite and diorite. The results of geochronology indicate that the granodiorite and diorite emplaced at 450 ± 3.9 Ma and 443 ± 4.0 Ma. Their emplacement time were well corresponding to the subduction stage of the Yunkai orogeny in the southwestern part of Cathaysia block during the Early Paleozoic (460–440 Ma). The Puyang adakite‐like granodiorite shows enrichments in Sr, but depletions in Y and Yb contents, high in Na2O, K2O and Al2O3, with εHf(t) values range from −10.5 to −7.4 (mean of −9.0) and two‐stage Hf model ages range from 1.91 to 2.10 Ga. These characteristics indicate that the magmas were generated by partial melting of subducted oceanic crust mixed with melts from the above wedgy mantle peridotite. The Puyang high‐Mg diorite shows enrichments in Sr and Ba, depletions in Rb, Y and Yb contents, and strongly high in MgO and Al2O3 contents, with εHf(t) values of −2.9 to 0 (mean of −1.4) and two‐stage Hf model ages of 1.43 to 1.61 Ga. These indicate that the magmas were mainly generated by partial melting of the wedgy mantle peridotite, mixed by adakitic melts from subducted oceanic slab. Comprehensive analysis shows that Puyang adakite‐like granodiorite and high‐Mg diorite were formed in fore‐arc setting, where the mantle and crustal magmas mixed during the oceanic subduction initiation period. By extension, this study offered important evidences to support the point that the Caledonian orogeny in South China was related to oceanic subduction which initiated prior to ~450 Ma.

Geochemical Criteria for Discriminating Shallow and Deep Environments in Oligocene-Miocene Succession, Western Iraq

The geochemical study of the Oligocene-Miocene succession Anah, Euphrates, and Fatha formations, western Iraq, was carried out to discriminate their depositional environments. Different major and trace patterns were observed between these formations. The major elements (Ca, Mg, Fe, Mn, K, and Na) and trace elements (Li, V, Cr, Co, Ni, Cu, Zn, Ga, Rb, Sr, Zr, Cs, Ba, Hf, W, Pb, Th, and U) are a function of the setting of the depositional environments. The reefal facies have lower concentrations of MgO, Li, Cr, Co, Ni, Ga, Rb, Zr, and Ba than marine and lagoonal facies but have higher concentrations of CaO, V, and Sr than it. Whereas dolomitic limestone facies are enriched V, and U while depletion in Li, Cr, Ni, Ga, Rb, Sr, Zr, Ba, and Pb Conversely, the lagoonal facies are rich in clay minerals and associated trace elements Li, V, Cr, Co, Ni, Cu, Ga, Rb, Zr, Ba, and Pb.

Simultaneous depletion of RB, RBL1 and RBL2 affects endoderm differentiation of human embryonic stem cells.

RB is a well-known cell cycle regulator controlling the G1 checkpoint. Previous reports have suggested that it can influence cell fate decisions not only by regulating cell proliferation and survival but also by interacting with transcription factors and epigenetic modifiers. However, the functional redundancy of RB family proteins (RB, RBL1 and RBL2) renders it difficult to investigate their roles during early development, especially in human. Here, we address this problem by generating human embryonic stem cells lacking RB family proteins. To achieve this goal, we first introduced frameshift mutations in RBL1 and RBL2 genes using the CRISPR/Cas9 technology, and then integrated the shRNA-expression cassette to knockdown RB upon tetracycline treatment. The resulting RBL1/2_dKO+RB_iKD cells remain pluripotent and efficiently differentiate into the primary germ layers in vitro even in the absence of the RB family proteins. In contrast, we observed that subsequent differentiation into foregut endoderm was impaired without the expression of RB, RBL1 and RBL2. Thus, it is suggested that RB proteins are dispensable for the maintenance and acquisition of cell identities during early development, but they are essential to generate advanced derivatives after the formation of primary germ layers. These results also indicate that our RBL1/2_dKO+RB_iKD cell lines are useful to depict the detailed molecular roles of RB family proteins in the maintenance and generation of various cell types accessible from human pluripotent stem cells.

Comparison of the Ediacaran and Cambrian petroleum systems in the Tianjingshan and the Micangshan uplifts, northern Sichuan Basin, China

Several different types of petroleum occurrences (including solid bitumens, oil sands, and oil seeps) are observed in various strata (e.g., the Ediacaran, Cambrian, Devonian, Permian, Triassic, and Jurassic strata) of the Tianjingshan and the Micangshan uplifts, northern Sichuan Basin, China. However, the sources of these petroleum occurrences are still in dispute, because of the severe biodegradation, strong thermal alteration, and multiple tectonic movements. At present, such uncertainty in the potential source rock systems has hindered oil and gas exploration in the study areas. In this study, methods including catalytic hydropyrolysis and trace elements analysis were introduced into the oil-source correlation study, to avoid the influence of biodegradation and/or thermal alteration. The results show that the petroleum shows that occur in the Cambrian-Jurassic strata of the Tianjingshan area are characterized by low maturity (equivalent vitrinite reflectance (EqVRo) < 1.0%), light organic carbon isotopic ratios (δ13Corg values ranging from −34.0‰ to −38.4‰), a predominance of C29-steranes, enrichment in V and Mo, and strong depletion in Bi elements. In contrast, the solid bitumens in the Ediacaran Dengying Formation in the Micangshan area have high maturity (EqVRo > 2.0%), slightly heavier δ13Corg values ranging from −27.5‰ to −36.0‰, a predominance of C27-steranes, weak enrichment in Mo and strong depletion in Rb and Bi elements. In addition, the Ediacaran and the Lower Cambrian source rocks can be discriminated by the bound sterane distributions, trace element concentrations, and bulk δ13Corg values. Further oil-source correlation indicates that the petroleum shows in the Cambrian-Jurassic strata in the Tianjingshan area were dominantly derived from the Lower Cambrian Qiongzhusi Formation, while those in the Ediacaran Dengying Formation in the Micangshan area were mainly sourced from the Ediacaran Doushantuo Formation. Finally, the results of oil-source correlation, combined with the tectonic evolution history of the investigated areas further elucidate the occurrence and distribution of petroleum, which can assist in oil and gas exploration in the investigated uplifts and the adjacent areas.

Response of trace elements to partial melting of felsic crust at high to ultrahigh temperatures: Implications for granite geochemistry

It is known that partial melting and melt extraction of crustal rocks result in chemical differentiation of the continental crust. But it is unknown how these two processes have affected the composition of granites due to a limited knowledge of trace element behaviors during crustal anatexis. In order to quantify this issue, a combined study of whole-rock and mineral trace elements and mineral modal proportions was conducted for high-temperature (HT) to ultrahigh-temperature (UHT) felsic granulites from the Tongbai orogen in central China. Reconstruction of LREE budgets suggests that LREE mainly reside in monazite in both HT and UHT granulites. As monazite is predicted to be not stable at UHT conditions in the modelling of previous studies, the presence of monazite in the Tongbai UHT granulites suggest that it was not sufficiently dissolved into anatectic melts. Considering monazite mainly occurs as interstitial grains, fast melt-residue separation may be the dominant factor for impeding its dissolution. Calculation of mineral/mineral trace element ratios indicates that K-feldspar has a higher capacity to accommodate Ba and Sr than biotite and plagioclase, with DBaK-feldspar/biotite of 2.5–3.0 and DSrK-feldspar/plagioclase values of 1.4–1.9, and ilmenite can preserve more Nb and Ta than biotite with DNbbiotite/ilmenite values of 0.07–0.1 and DTabiotite/ilmenite values of 0.04–0.05. In addition, partitioning of first row transition elements (FRTE) was constrained in the felsic granulites, with preference of Sc into garnet, and Co, V, Ni, and Cr into biotite. Modelling based on the presently constrained partition coefficients indicates that trace elements show consistent differentiation trends during anatexis of various felsic rocks, with enrichment of Sr, Ba, Nb, Ta and FRTE but depletion of Rb in anatectic restites. The high DNb/Ta values of biotite and ilmenite cause the residues produced by biotite dehydration melting to be commonly of higher Nb/Ta ratios than protoliths, indicating that the residues are potentially high Nb/Ta reservoirs. In contrast, the change of peritectic minerals due to various protolith compositions and melting conditions results in differential responses of Sr, Ba, and FRTE to partial melting, suggesting that these elements may be useful indicators to trace the petrogenetic process of granites. The correlation between Ba and Sc contents or between Sr/Ba and Sc/Co ratios is demonstrated to be a valid index in discriminating melts from metagreywackes and metapelites due to different modes of garnet, orthopyroxene, and K-feldspar in their anatectic residues. Moreover, as the proportions of garnet and orthopyroxene in the residues are significantly influenced by melting pressures, the Sc/Co ratio and Sc content of granites can be used to trace their anatectic depth.

Zircon as a Recorder of Trace Element Changes during High-Grade Metamorphism of Neoarchean Lower Crust, Shevaroy Block, Eastern Dharwar Craton, India

AbstractSystematic changes in whole-rock chemistry, mineralogy, mineral textures, and mineral chemistry are seen along a ca. 95-km traverse of late Archean granitoid orthogneisses in the Shevaroy Block, Eastern Dharwar Craton, southern India. The traverse passes from amphibolite-grade gneisses in the north to granulite-grade rocks (charnockite) in the south. Changes include whole-rock depletion of Rb, Cs, Th, and U in the granulite grade rocks as relative to the amphibolite grade gneisses, and oxidation trends regionally from highly oxidised granulite-facies rocks near the magnetite–haematite buffer to relatively reduced amphibolite-facies rocks below the fayalite-magnetite-quartz. Rare earth elements show limited mobility and are hosted a variety of minerals whose presence is dependent on the metamorphic grade ranging from titanite and allanite in the amphibolite-facies rocks to monazite in the vicinity of the orthopyroxene-in isograd to apatite in the granulite-grade charnockite. Cathodoluminescence and back-scattered electron sub-grain imaging and sensitive high-resolution ion microprobe analysis of zircon from 29 samples of dioritic, tonalitic, and granitic orthogneiss from the traverse reveals magmatic zircon cores that record the emplacement of the granitoid protoliths mostly about 2580 to 2550 Ma, along with a few older mid to late Archean tonalites. Protolith zircon was modified during metamorphism by overgrowth and/or replacement. Relative to igneous cores, U-enriched metamorphic zircon, dominant in the amphibolite-grade gneisses, formed at ca. 2530 Ma, predating retrograde titanite growth at ca. 2500 Ma. Uranium-depleted mantles grew on zircon between 2530 and 2500 Ma in granulite-grade samples south of the orthopyroxene-in isograd. In some of these samples, the U-depleted metamorphic zircon is preceded by mantles of U-undepleted zircon, indicating a progression of metamorphic zircon growth with increasingly depleted compositions between 2530 and 2500 Ma. With increasing metamorphic grade (from amphibolite to granulite) and oxidation state, allanite and monazite disappear from the assemblage and zircon became depleted in U and Th. Whole-rock U-Th compositions became decoupled from relict magmatic zircon compositions, reflecting the development of U-depleted metamorphic zircon and indicating that whole-rock chemical differences along the traverse were produced during metamorphism, rather than just reflecting differences in dioritic vs granitic protoliths. Although in situ anatexis and melt extraction may have played a role, whole-rock and zircon depletion of trace elements can be explained by the action of externally derived, oxidising, low-H2O activity hypersaline fluids migrating up through the mid to lower crust. Fluids and element migration during metamorphism may be the end result of subduction related processes that cumulated in the collision and concatenation of island arcs and continental blocks. These tectonic processes assembled the Dharwar Craton at the end of the Archean.

Genetic link between the Late Mesozoic granitic magmatism and W mineralization in NE China: Constraints from in-situ U-Pb geochronology and geochemistry of wolframite, and whole-rocks geochemistry analyses of W-bearing granites from the Sansheng W-Mo deposit

The Sansheng quartz-vein type W-Mo deposit is located on the southern margin of NE China. Tungsten mineralization occurs mainly in veins and veinlets within the Early Cretaceous granitic pluton. In-situ U-Pb dating of hydrothermal wolframite yields a W mineralization age of 137.3 ± 2.0 Ma (1σ, MSWD = 4.4), which provides evidence for an Early Cretaceous W mineralization event in the Sansheng area. W-bearing granites show petrological, mineralogical, and geochemical characteristics of highly fractionated A-type granites. The rocks belong to the high-K calc-alkaline series and are characterized by the enrichment in large ion lithophile elements (e.g., Rb, Th, U, and K) and significant negative Eu, Ba, Sr, P, and Ti anomalies. They also have higher W concentrations, Rb/Sr and U/Th ratios, and lower (La/Yb)N, LREE/HREE, Eu/Eu*, K/Rb, Zr/Hf, Nb/Ta, and Y/Ho ratios than the contemporary W-barren granitoids in NE China. The geochemical signatures of the W-bearing granites indicate that the primary magmas were derived from partial melting of the lower crust and subsequently underwent extensive fractional crystallization. The W mineralization in the Sansheng is genetically related to the W-bearing granites, and extreme fractional crystallization was critical for W enrichment in granitic magma. The trace element compositions of the wolframite show similar enrichments in HREEs, Nb, Ta, and U, as well as depletion in LREEs, Rb, Ba, Th, Pb, Sr, and Ti, compared to those of the upper continental crust. We demonstrate that isovalent substitution mechanisms could have played critical roles in the formation of hydrothermal wolframite in the Sansheng deposit, and the chemical composition of wolframite is controlled by both the crystallochemical parameters and composition of the primary hydrothermal fluids. In the context of the regional geology, the new data suggest that the Sansheng W-bearing granites and corresponding mineralization formed in a post-collisional extensional setting controlled by the closure of the Mongol-Okhotsk Ocean and the rollback of the Paleo-Pacific Ocean plate during the Early Cretaceous.

Mapping Co–Cr–Cu and Fe Occurrence in a Legacy Mining Waste Using Geochemistry and Satellite Imagery Analyses

Abandoned mining wastes are both an environmental challenge and a possible secondary raw material source. The characterization and monitoring of these sites are often expensive and cumbersome because of the need of repeated field surveys. Remote sensing data are a cost-effective alternative that helps in producing multiscale maps of mining wastes. These maps can be used to investigate and monitor the spatial patterns of different elements within the mining wastes. In this work, Sentinel-2 images are combined with the geochemical samples in order to map the distribution of iron, copper, chromium, and cobalt. The target area was the Vigonzano mining wastes in Northern Apennines (Italy) where there are a small number of geochemical analyses but a large amount of satellite image data. We used the multivariate geostatistical estimation method (Co-Kriging) that exploit the meaningful spatial correlation between the elements of interest and band ratios (obtained from Sentinel-2 images). The concentration maps highlighted subareas for Cu and Cr with an estimated grade of about 0.3% and 0.2%, respectively. In addition, the critical element Co showed an enrichment in the south-east part of the mining wastes, in a similar pattern as Cr. Instead, the obtained maps show Ce, La, Rb, and Nb depletion compared to the surrounding agricultural areas. The concentration maps were intended as a prefeasibility study to determine enriched areas for further detailed investigation.

Beryl as indicator of metasomatic processes in the California Blue Mine topaz-beryl pegmatite and associated miarolitic pockets

Beryl occurs in a wide variety of rare-element pegmatites and has provided significant insights into their evolution. The geochemical signatures of beryl can record igneous and metasomatic processes but rarely could they be studied at the same location in both, the pegmatite body and associated miarolitic pockets. Further, the link between beryl chemistry and the petrogenesis of pegmatites has not yet been established convincingly. This study focuses on the recently discovered topaz-beryl granitic pegmatite deposit at the California Blue Mine in San Bernardino County, California, USA. This pegmatite deposit provides an exceptional opportunity to study microtextural (SEM and WDS-element maps) and major EMPA and trace element LA-ICP-MS concentrations in beryl in the pegmatite body and associated miarolitic pockets. The mineralogy of the pegmatites consists of: quartz + K-feldspar + albite (i.e., cleavelandite variety) + biotite + muscovite ± spessartine ± beryl (i.e., aquamarine variety) ± topaz, with a mineralogic zoning that includes border, wall, intermediate, and core zone. The miarolitic pockets contain gem quality beryl, topaz, and quartz crystals. Two major beryl types were distinguished including a primary (Brl I) and a metasomatic beryl (Brl II). Brl I occurs in the intermediate pegmatite zone and displays a blocky concentric crystal zoning characterized by a core enriched in Al and rims enriched in Na, Rb, K, and Sc. In contrast, Brl II is found mostly in the pegmatite core zone and at the contacts to, or within miarolitic pockets, and is characterized by a distinct enrichment in Cs and Li correlating with an enrichment in Na, B, and As and a depletion in Rb, K, Sc, and Fe. Brl II occurs as two variants including as replacement of Brl I (i.e., dissolution-precipitation microtextures in the pegmatites) and as single hydrothermal crystals (i.e., precipitation in the miarolitic pockets). The contrasting trends between Brl I and Brl II are interpreted to reflect two distinct processes affecting trace element variations in beryl including fractionation from a magma with systematic crystal core to rim zoning (decreasing Li and enrichment in Na, K, Rb, Sc, and Fe), and metasomatism with enrichment in Li, Cs, Na, B and As. An extensive beryl trace element dataset was generated in this study and further compared to beryl of the NYF (Nb-Y-F) and LCT (Li-Cs-Ta) pegmatite families worldwide. A significant link was found between beryl chemistry and the petrogenetic relationships of the pegmatites, which were used to distinguish four major geochemical beryl groups: (i) a low and a high Fe–Mg — alkali group, both displaying a positive alkali vs. Fe + Mg correlation; (ii) a low Fe–Mg — high alkali group displaying a negative alkali vs. Fe + Mg correlation; (iii) a low Li–Cs group; (iv) a high Li–Cs group. The more evolved LCT-type pegmatites generally overlap with the low Fe–Mg — high alkali and high Li–Cs groups (ii and iv). In contrast, NYF pegmatites coincide better with the trends observed for the low Li–Cs group as well as the low/high Fe–Mg — alkali beryl groups displaying a positive Fe + Mg vs. alkali correlation (i and iii). The beryl signatures from the California Blue Mine coincide with the NYF pegmatite classification but a partial overlap with the LCT pegmatites indicates a possible mixed origin or crustal contamination (i.e., hybrid pegmatites). These new insights reveal that beryl signatures provide a significant tool for interpreting the evolution of pegmatites from different geologic settings and permits distinguishing between igneous and metasomatic origins.

Lost at sea: Identifying the post-depositional alteration of amphorae in ancient shipwrecks

The present paper sheds new light on the alteration of archaeological ceramics buried in marine environments by analysing in detail a large dataset of Hellenistic and Late Roman Republican transport amphorae from 15 sites along the well-known ancient maritime trade route off the Dalmatian coast in southern Croatia. These include amphorae from shipwrecks, kiln sites and settlements. Ceramic petrography and instrumental neutron activation analysis (INAA) have been used to compare sherds of amphorae made in the same workshop, of the same fabric and origin, but recovered from both shipwrecks and terrestrial sites and were therefore exposed to different burial environments over two millennia. The integration of both methods permitted the identification of differential microstructural and geochemical alteration of the amphorae under the sea relative to those found on land. By applying principal components analysis and test statistics, we have detected enrichment of As, Ca, Na, Sb, Sr and U and depletion of Ba, Cs, K and Rb in amphorae from the marine environment, relative to those buried on land. The implications of the study are discussed in terms of the provenance determination of amphorae from submerged environments and the reconstruction of ancient maritime trade routes.

Element mobility as a proxy for delineating shear zone boundaries in orogenic belts: A case study of Iwaraja shear zone, southwestern Nigeria

Shear zones are localised regions of intense deformation and are important archives of element mobility history during crustal deformation. The boundary is determined by examining shear deformation fabrics in affected rocks. However, the "mixture" of relicts of undeformed rocks coupled with newly formed shear fabrics affect the determination of the internal boundaries of the shear zone and its boundary with the unsheared protolith, which in turn limits the evaluation of the shear zone's width. A new approach involving element mobility across the shear zone is proposed as a proxy to address this problem and corroborate existing methods. The petrographic and geochemical analyses of granitic gneiss across the Iwaraja shear zone and its adjacent rock were carried out. The element mobility patterns and volume of chemical changes were evaluated using isocon and Cartesian element-distance plots to interpret the chemical changes in the granitic gneiss across the shear zone. The result indicates a very high enrichment of TiO2, Fe2O3, MnO, MgO, P2O5, and REEs with relatively similar mobility patterns and a high depletion of Na2O, Rb, and Th in the shear zone. Al2O3 is not significantly mobilized but the mobility pattern of K2O is erratic. Based on the chemical changes in the granitic gneiss, the ductile shear zone is a CaO–MgO–Fe2O3-REE-enriched and Na2O–Rb–Th-depleted system. Under greenschist facies condition, the chemical mobility of TiO2, MnO, P2O5, Th, Rb, Zn, Ba, Zr, Th, Hf, and REEs is sensitive to the changes in the deformation intensity between the strongly- and weakly-deformed zones whereas REE [Lu, Yb, Gd, Eu, Ho, Tb] is useful to determine the boundary between the weakly-deformed zone and the unsheared rock. These index minerals are useful in other similar ductile shear zones in any orogenic belt. Based on the element mobility patterns, the width of the affected granite gneiss in the shear zone is ~680 m.