Low CaO Contents Research Articles

Effect of CaO content in raw material on the mineral composition of ferric-rich sulfoaluminate clinker

Ferric-rich calcium sulfoaluminate (FR-CSA) cement is an eco-friendly cement. Fe2O3 exists in different minerals of FR-CSA clinker, e.g., Ca4Al2Fe2O10 (C4AF), Ca2Fe2O5 (C2F), and Ca4Al6-2xFe2xSO16 (C4A3-xFxS-). The mineral composition depends on the chemical composition of the raw materials and significantly determines the reactivity of FR-CSA cement. To optimize the phase composition of the FR-CSA clinker, chemical reagent raw mixtures with different amounts of CaO were used to prepare the FR-CSA clinker. X-ray diffraction (XRD) analysis, Rietveld quantitative phase analysis (RQPA), Fourier Transform Infrared spectroscopy (FT-IR), and scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) were used to identify the mineralogical conditions of the FR-CSA clinker. The results indicated that the amounts of CaO in raw materials greatly affected the iron-bearing phase formation in the FR-CSA clinker. With decreasing CaO content involved in calcination reaction, the amounts of Fe2O3 incorporated in C4A3-xFxS- increased up to 17.72 wt% (where x = 0.36). The findings make it possible to optimize the mineral composition of the FR-CSA clinker by changing the CaO content in raw materials. Furthermore, low CaO content in the raw material is beneficial to the formation of C4A3-xFxS-, which enables the use of solid wastes containing low calcium for producing FR-CSA cement.

Petrogenesis and tectonic implications of Palaeocene (ca. 54 Ma) rhyolites in the western Lhasa Terrane, south Tibet: Constraints from geochemistry and Sr–Nd–Hf isotope compositions

The widespread Linzizong volcanic successions (LVS) in the Lhasa Terrane was a magmatic response to the tectonic transition from Neo‐Tethyan oceanic subduction to the India–Asia collision, which has been the subject of many studies; however, studies on the LVS in the western Lhasa Terrane are scarce compared to those in the east, limiting our understanding of the tectonic transition. Zircon U–Pb ages of two rhyolitic samples from the Shiquanhe region in the west of the Lhasa Terrane indicate that at least part of the Zenong Group, previously thought to have formed during the Early Cretaceous, was actually erupted during the Late Palaeocene (ca. 54 Ma) and belongs to the LVS. The rhyolites are characterized by high SiO2 and Al2O3, moderate K2O and Na2O, and low MgO, CaO, and FeO contents, enrichment in Rb and Th, depletion in Sr, Ba, Eu, Nb, and Ta, and have relatively uniform whole‐rock εNd(t) (−1.90 to −0.89) and zircon εHf(t) (+0.95 to +5.03) values. These geochemical characteristics indicate that they were formed by the partial melting of juvenile continental crust with subsequent plagioclase, biotite, amphibole, and Fe–Ti oxide fractionation. Combined with the results of previous studies, our data show that the western Lhasa Terrane underwent intensive Early Cenozoic crustal growth, similar to what occurred in the east, due to underplating of mantle‐derived magma resulting from the roll‐back and eventual break‐off of the Neo‐Tethys slab after the initial continental collision.

Mineral chemistry of high-Al chromian spinel from ultramafic rocks of the Babina–Prithvipur transect, Bundelkhand Craton, central India: Implication for petrogenesis and tectonic setting

Bundelkhand Craton is an important Archaean cratonic nuclei of the Central Indian Shield and comprises two greenstone complexes, i.e., the Babina–Mauranipur Greenstone Belt and the Girar–Madawara Greenstone Belt. The E–W trending Babina–Mauranipur Greenstone Belt in the central part of the craton, encloses several isolated lensoid shaped ultramafic bodies which has suffered various degrees of alteration and metamorphism. As per modal mineral analysis, the ultramafic rocks of the Babina–Prithvipur section belong to harzburgite and also contain high-Al chromian spinel along with olivine, ortho-pyroxene and amphibole. Mineral chemistry reveals that the spinels are of high Al and Cr poor variety, where Al2O3 and Cr2O3 contents range from 40.06 to 54.34 wt.% and 9.05 to 14.89 wt.%, respectively. The TiO2 content is extremely low (average ≈0.07 wt.%). The Cr# value of the spinel is <0.2, whereas Mg# ranges from 0.495 to 0.633. The forsterite contents of the olivine ranges from 86.088 to 88.105 wt.%. Average CaO and NiO contents of the olivine stand 0.03 and 0.24 wt.%, respectively. Composition of the analyzed ortho-pyroxene belongs to En84.20–87.75Wo0.15–0.39 with low CaO content of 0.080 to 0.207 wt.%. As per mineral chemistry, these harzburgite rocks of the Babina–Prithvipur section belong to mantle peridotite. Melt calculation for the spinel also suggests a least differentiated magmatic product, which is also supported by the olivine spinel mantle array diagram as all the samples are plotted within the mantle array field very close to the fertile mantle source. Low TiO2 and high Al contents of spinel also reflect the MORB type peridotite characteristics for these ultramafic rocks which probably originated from least differentiated plagioclase free mantle derived harzburgite/lherzolitic magma in a rift related spreading centre. As a whole these ultramafic rocks appear to be the remnant of the early crust that existed during the Archaean time.

Provenance and paleo-weathering of Paleoproterozoic siliciclastic sedimentary rocks of Bijawar Group, Sonrai Basin, Uttar Pradesh, India: using a geochemical approach

Shales and sandstones of the Paleoproterozoic Bijawar Group (India) have been studied to decipher their paleo-weathering conditions and provenance based on geochemistry. Shale samples are composed of k-feldspars, mica, quartz, and fine iron-oxides, whereas sandstones are composed of quartz and k-feldspars. The predominant positive correlation of K2O vs TiO2, Na2O vs Al2O3, and K2O vs Al2O3 indicates that the elements are associated with detrital phases. Trace elements Sc, Rb, Ba,Th, Y, and Zr show a strong positive correlation with Al2O3 and K2O which indicates that the absolute abundances of these elements are controlled mainly by illite. A negative correlation of trace elements Ni, Cu, Co with Al2O3, and K2O represents their presence in iron oxides like magnetite, ilmenite, and hematite. Multi-element Post-Archaean Australian Average Shale (PAAS) normalized spider diagrams show enrichment of V, Pb, Zr, Y, Hf, Th, Rb, and depletion of Ni, Sr, Ba, Nb, U. The depletion of Sr indicates the least enrichment of plagioclase and the same is also supported by negative Eu-anomaly of the samples, though weak. The chondrite normalized rare earth element (REE) plots show a slightly light-REE (LREE) enriched and flat heavy-REE (HREE) pattern with weak negative Eu anomaly. The overall, high values of LaN/SmN (avg. 10.49), CeN/YbN (avg.0.37), LaN/YbN (avg. 34.28) and low values of GdN/YbN (avg. 1.82) and TiO2 (0.27–1.82, average 0.92 < PAAS) in most of the samples, show a relationship with the felsic source rocks. The index of compositional variability (ICV) of the samples is < 0.84 which indicates no enrichment of primary minerals. The chemical index of alteration (CIA) of present samples varies from 48.60 to 81.69, indicating low to moderate intensity of chemical weathering of the source. The plot between SiO2 and Al2O3 + K2O + Na2O depicts that majority of the samples belong to the environment from humid to semi-humid and have attained a high chemical maturity. The high SiO2/Al2O3 values (1.36–20.79) in studied samples indicate relatively high sediment maturity due to the extreme sorting of sediments in a stable cratonic regime. A stable cratonic regime, with a low upliftment rate that has allowed strong chemical weathering of protoliths, is further indicated by low CaO, Na2O, and Sr contents of the studied samples. The overall geochemical characteristics of the present samples—high SiO2, Al2O3 and K2O and low TiO2, MgO, Na2O, and CaO contents—suggest a felsic provenance. The felsic nature of the source rocks is also supported by the trace element ratios like (La/Lu)N (7.72–76.89), La/Sc (1.50–7.40), La/Co (0.39–11.48), Th/Co (0.80–15.90), and Cr/Th (0.08–5.10). Since the Bijawar Group is sited over the Bundelkhand Granite Gneiss Complex (BGGC), it is, therefore, plausible that the main source components of Bijawar Group siliciclastic rocks are the BGGC felsic rocks.

Calibration of the biotite-muscovite geobarometer for metapelitic assemblages devoid of garnet or plagioclase

Determination of metamorphic pressure (P) – temperature (T) conditions of metapelitic assemblages sometimes suffers from low-CaO content of garnet and/or plagioclase, thus the garnet-plagioclase-related geobarometers lose their usage under such circumstances. Therefore, calibration of garnet-plagioclase-absent geobarometers is very useful. In this paper, the biotite-muscovite geobarometer was empirically calibrated under P-T conditions of 1–12 kbar and 470–760 °C using 270 natural metapelite samples. About 86.5% of the total calibrant samples yielded similar biotite-muscovite pressure estimates to the well-calibrated garnet-Al2SiO5-plagioclase-quartz (GASP) geobarometer within error of ±1.5 kbar. The total error of the biotite-muscovite geobarometer is estimated to be less than ~±1.6 kbar. The applicability of the biotite-muscovite geobarometer has been certified through application to natural metapelite samples coupled with the Ti-in-biotite geothermometer. When garnet and/or plagioclase are absent in metapelitic assemblages such as two-mica schist / gneiss, this geobarometer may play its unique and irreplaceable role. An electronic spreadsheet (Table S3) is deposited at the journal's website for iterative application of the biotite-muscovite geobarometer in combination with the Ti-in-biotite geothermometer.

Phase Equilibrium Diagram for Electric Arc Furnace Slag Optimization in High Alloyed Chromium Stainless Steelmaking

The electric arc furnace (EAF) process for steelmaking of Cr and Ni high alloyed stainless steel grades differs significantly from the steelmaking process of carbon steel due to the special raw materials and generally lower oxygen consumption. The special slag chemistry in the EAF process affects slag foaming and refractory wear characteristics due to an increased content of CrOx. A special slag diagram is presented in order to improve monitoring and control of slag compositions for Cr alloyed heats, with special focus on saturation to MgO periclase and dicalcium silicate C2S in order to minimize MgO losses from the refractory lining and to improve slag refining capability by avoidance of stable C2S. With the same diagram different EAF process strategies can be efficiently monitored, either at elevated CaO and basicity with lower spinel concentration and more liquid process slags near C2S saturation or at lower CaO content and basicity with increased spinel concentration and stiffer slags at MgO saturation but certainly no C2S stability. Examples for three industrial EAFs are given.

Detecting Coastal Atmosphere Weathering Process on Andesite Rock Using Magnetic Susceptibility and Fe3O4/Fe2O3 Ratio

Weathering is a geological phenomenon that is often an important considered because of its destructive properties, mainly in subsurface. Many parameters are used to measure the presence of weathering indications. This study focuses on testing of magnetic susceptibility (c), compound oxide content and Fe3O4/Fe2O3 ratio that have been selected as an indicators of weathering process. This study explains in detail the quantitative analysis of weathering based on these parameters in basaltic andesite rocks found in coastal atmospheric areas. The results obtained for weathered rocks, magnetic susceptibility, compound oxide content such as CaO and the Fe3O4/Fe2O3 ratio has decreased significantly. In the coastal atmosphere, the weathering of basaltic andesite rocks also marked by the distribution of magnetic minerals which tend to be in the domain of pseudo single domain (PSD) or single domain (SD). Thus it can be concluded that both of low frequency magnetic susceptibility (clf), CaO and Fe2O3 content and also the Fe3O4/Fe2O3 ratio can be used as weathering level indicators.

Mineralogy, isotope geochemistry and ore genesis of the miocene Cuonadong leucogranite-related Be-W-Sn skarn deposit in Southern Tibet

The Himalayan orogenic belt is characterized by widespread leucogranites, which are mostly peraluminous with less than 5% mafic minerals. Previous studies mainly focused on the petrological characteristic, genetic mechanism, magmatic evolution and tectonic significance of these leucogranites. However, recently, a skarn-type Be–W–Sn polymetallic deposit, which is spatially related to the Cuonadong leucogranites of the Himalayan leucogranites belt, was discovered. The orebodies occur in the inner and outer contact zones between the Cuonadong leucogranites and their surrounding marble. This study focuses on the the characteristics of the skarn mineral assemblages. The deposit shows a typical skarn mineral zonation, from inside to outside, including dark pyroxene-garnet skarn zone, red garnet zone, dark green amphibole-specularite zone, light-green vesuvianite-epidote ribbon, and vesuvianite-chlorite zone. Zircon U-Pb dating shows that the ore-related leucogranite was emplaced at ca. 18 Ma. Geochemically, the leucogranite has high SiO2, Al2O3, Na2O, K2O and low CaO contents belonging to peraluminous granite. The Cuonadong leucogranite is characterized by right-dipping chondrite-normalized REE patterns with distinct negative Eu anomalies. Importantly, all samples show Lanthanide tetrad effect on chondrite-normalized REE patterns, indicating significant melt-fluid interaction has occurred due to strong fractional crystallization. Additionally, the Cuonadong leucogranite is enriched in large ion lithophile elements (such as Rb) and relatively depleted in high field strength elements (such as Nb, Zr, Hf), suggesting a crustal source region. High F and B contents in the magma could have significantly increased the solubility of water in the magma, while the magmatic-hydrothermal solution enriched in F and B should have remarkably enhanced the metal-carrying capacity and increased the permeability of surrounding rocks, which in turn effectively facilitated water–rock reaction.

Uranium Mineralogical and Chemical Features of the Na-Metasomatic Type Uranium Deposit in the Longshoushan Metallogenic Belt, Northwestern China

The Longshoushan Metallogenic Belt (northwestern China) is known for its word-class Jinchuan Ni-Cu sulfide (Pt) deposit and is also an important uranium metallogenic belt. The Jiling uranium deposit in this belt is a typical Na-metasomatic uranium deposit, which rarely occurs in China. Mineralization in the Jiling uranium deposit is hosted in granitoids that have suffered a Na-metasomatic alteration. There are three kinds of uranium minerals, including uraninite, pitchblende, and coffinite in the Jiling uranium deposit. Pitchblende is the predominant uranium mineral. Integrating the mineralogy and geochemistry of uranium minerals, and in situ electron microprobe analyzer (EMPA) U-Th-Pb chemical dating, we aimed to unravel the age and nature of the mineralization, to decipher the characteristics of the hydrothermal alteration and the U mineralization process. Based on the microtextural features and compositional variations, primary uraninite was altered to uraninite A and B, and fresh pitchblende was altered to pitchblende A and B. The best-preserved uraninite crystals displayed a euhedral-shape with high Pb and low SiO2, CaO, FeO, and Al2O3 contents, and was interpreted as primary uraninite. The EMPA U-Th-Pb chemical ages revealed that uraninite may have formed at 435.9 ± 3.3 Ma. High ThO2 + ΣREE2O3 + Y2O3 contents illustrated that the best preserved uraninite crystallized at a high temperature. Altered pitchblende A showed a relatively brighter gray color in backscattered electron (BSE) images and with a lower SiO2 content than B. Three analysis spots of the fresh pitchblende showed low contents of ΣSiO2 + CaO, indicating no obvious alteration. EMPA U-Th-Pb chemical dating gave a mean chemical age of 361 Ma. The low Th + ΣREE2O3 contents indicated that this pitchblende formed at a relatively low temperature. According to the different characteristics of occurrence and chemical composition, the coffinite in the Jiling uranium deposit can be divided into coffinite A and B, respectively. The compositional variation of the fresh and altered uraninite and pitchblende indicated that both uraninite and pitchblende underwent at least two discrete hydrothermal fluid alterations. The U mineralization was divided into two stages; uraninite was formed at a high temperature and possibly from a magmatic-hydrothermal fluid during ore stage I. Then, pitchblende was formed at a low temperature, during ore stage II. According to the petrographic observations and their chemical compositions, coffinite A and B resulted from the alterations of uraninite and pitchblende, respectively.

Influence mechanism of silicon content in Al-killed steel on compositions of inclusions during LF refining

ABSTRACT To obtain solid inclusions in LF refining process, the influence of silicon content in steel on compositions of inclusions during LF refining were investigated in Al-killed steel. Influence of silicon on compositions of inclusions was found to be great. The [Ca] content of steel was supplied from the reaction of [Al] and CaO. The [Si] content affected the [Ca] content by the reaction (SiO2) + 2[Ca]→[Si]+2(CaO), and [Ca] was consumed more readily by SiO2 in Si-free steel than in Si-containing steel, as a result, Al2O3 and MgO·Al2O3 inclusions could be obtained in Si-free steel, whereas calcium aluminate inclusions were found in Si-containing steel. Moreover, the inclusions were mainly solid Al2O3 with low contents of CaO and MgO when using low-calcium ferrosilicon alloy and adding all low-calcium ferrosilicon alloys required for the steel at the end of LF refining, this ensures high removal efficiency of inclusions in RH degassing.

Melting relations of anhydrous olivine-free pyroxenite Px1 at 2 GPa

Abstract. The reaction between melt derived by mafic heterogeneities and peridotites in an upwelling mantle may form hybrid olivine-free pyroxenites. In order to evaluate the impact of these lithologies on the chemistry of primitive magmas and their ability to give rise to new mantle heterogeneities, we experimentally investigate the melting relations at 2 GPa of the model olivine-free pyroxenite Px1 (XMg=0.81, SiO2=52.9 wt %, Al2O3 = 11.3 wt %, CaO = 7.6 wt %). The subsolidus assemblage consists of clinopyroxene, orthopyroxene, and garnet. At 2 GPa, the solidus of Px1 is located between 1250 and 1280 ∘C, at a temperature about 70 ∘C lower than the solidus of fertile lherzolite. At increasing melt fraction, the sequence of mineral phase disappearance is garnet–clinopyroxene–orthopyroxene. Across the solidus, partial melting of Px1 is controlled by reaction garnet + clinopyroxene = liquid + orthopyroxene, and above 1300 ∘C, once garnet is completely consumed, by reaction clinopyroxene + orthopyroxene = liquid. Orthopyroxene is the liquidus phase, and at 1480 ∘C olivine-free pyroxenite Px1 is completely molten indicating a melting interval of about 200 ∘C. Isobaric melt productivity is similar to garnet clinopyroxenites, and it is more than 3 times that of a fertile lherzolite at 1400 ∘C. Px1 partial melts cover a wide range of XMg (0.57–0.84), with SiO2, Al2O3 and Na2O decreasing and Cr2O3 increasing with the degree of melting. CaO content in partial melts increases as long as clinopyroxene is involved in melting reactions and decreases after its exhaustion. At 2 GPa and for melting degrees higher than 10 %, Px1 produces MgO-rich basaltic andesites matching the composition of eclogitic melts in terms of silica and alkali contents but with significantly higher XMg values. These melts differ from those derived from lherzolites at 2 GPa by higher SiO2 and lower CaO contents. Their high silica activity makes them very reactive with mantle peridotite producing hybrid orthopyroxene-rich lithologies and residual websterites. Melt–rock reactions likely prevent direct extraction of melts produced by olivine-free pyroxenites.

Petrology of a Neoproterozoic mantle peridotite–chromitite association from Abu Dahr area, Eastern Desert, Egypt: Infiltration of a boninitic melt in highly depleted harzburgite

Peridotites of Abu Dahr represent the main litho–unit of a Neoproterozoic dismembered ophiolite sequence and are among the best–preserved and well–exposed mantle rocks in South Eastern Desert of Egypt. Here, we present new geochemical and mineral chemical data for peridotites and associated pyroxenites and for chromitites and their platinum–group minerals to constrain their petrogenesis and geotectonic setting. The Abu Dahr ophiolite mantle section consists mainly of harzburgites, cut by pyroxenite dykes and containing dunite–chromitite lenses. The harzburgites are composed of olivine, orthopyroxene, spinel and minor clinopyroxene (˂1.0 vol %) and amphibole. Olivine from harzburgites is highly magnesian (Fo 91–93) and Cr–spinel shows a wide–range of Cr2O3 and Al2O3 contents. The enstatite component of orthopyroxene decreases from harzburgite (En = 90–91) to orthopyroxenite (En = 84–87). Amphiboles are represented by magnesiohornblende and tschermakite. The chromitites are massive to disseminated and composed of magnesiochromite with high Cr# (83–93) and Mg# (66–79), and low TiO2 (<0.1 wt%) content. Solid inclusions in chromite include olivine, orthopyroxene and hornblende. Laurite (RuS2) is the most common PGM detected in the investigated chromitite samples and forms micrometer–size inclusions in fresh chromite. Various Ni–sulfides are found both in fresh chromite and along serpentine veinlets. Harzburgites have a refractory composition with a very low Al2O3 (0.4–0.8 wt%) and CaO (0.2–1.6 wt%) contents and high bulk–rock Mg# (89–92). Geochemical data suggest that the Abu Dahr peridotites are highly depleted SSZ peridotites formed in a forearc mantle wedge setting by high degrees of hydrous partial melting and emplaced as a result of the collision of the intra–oceanic arc with the Beitan gneisses. The podiform chromitites and orthopyroxenites were formed due to impregnation of mantle wedge harzburgites by boninitic melt. The highly depleted nature of the harzburgite is responsible for the small reserves of chromite ore at Abu Dahr and in the South Eastern Desert in general.

Origin of the Triassic Lincang granites in the southeastern Tibetan Plateau: Crystallization from crystal mush

The crustal generation of the Paleo-Tethys orogenic belt in the southeastern Tibetan Plateau is a major unresolved geological problem. The Changning-Menglian suture in the southeastern Tibetan Plateau represents a remnant of the Paleo-Tethys Ocean. The Lincang batholith and associated volcanic rocks (the Manghuai rhyolites and Xiaodingxi basalts) are located to the east of the Changning-Menglian suture, and represent important constraints for the abovementioned geological problem. New zircon UPb ages, together with previously published results, indicate that the Manghuai rhyolites were emplaced at 229–239 Ma and the Lincang batholith yielded longer age span (211–239 Ma). Broad age span of zircons (to 28 million years) from these rocks record a long-lived crustal magmatic system in the Changning-Menglian Paleo-Tethys orogenic belt. These intrusive and associated volcanic rocks have significant differences between them in terms of geochemistry. In this study, these rocks are geochemically classified into three groups: (1) Group 1 comprises biotite granite and granodiorite rocks; (2) Group 2 includes alkali feldspar granite, two-mica granite, and rhyolite, which are high-silica (generally >70 wt%) rocks that have low TiO2, Al2O3, FeOtot, MgO, CaO, P2O5, Eu, and Sr contents, compared to those of Group 1. Based on their geochemical relationships and mineral textures, Groups 1 and 2 include cumulative- and fractionated-type granitoids, respectively; (3) while Group 3 is comprised of dioritic enclaves and the Xiaodingxi basalts. Based on more robust evidence, dioritic enclaves are derived from a mantle source magma. The Lincang granites have high and variable initial 87Sr/86Sr ratios (0.703122–0.728476), significantly negative εNd (t = 220 Ma) values (−13.4 to −7.5), negative εHf (t) values (−17.7 to −6.8), and old TDM2 ages. The Manghuai rhyolites and Xiaodingxi basalts have lower initial 87Sr/86Sr ratios (0.695970–0.709398), and higher εNd (t) values (−3.4 to −0.6) and εHf (t) values (−1.2 to +3.7) than those of the Lincang granites. Geochemical data suggest that the Manghuai rhyolites could be seen as fractionated and erupted melts from crystal mush reservoirs, which later crystallized to form the Lincang granites. The Manghuai rhyolites provide an instantaneous snapshot of the state of the crystal mush at the time of eruption. The Lincang granites are interpreted to record prolonged histories of open-system magmatic evolution, involving magma mixing, wall-rock assimilation, and multiple cycles of crystallization from the crystal mush reservoirs. Magmatic evolution was likely related to mantle upwelling in a post-collisional setting, forming large-volume granites and volcanics in the Changning-Menglian Paleo-Tethys orogenic belt. Thus, this crystal mush model provides an integrated picture of the Triassic silicic magmatism, linking the evolution of the Lincang batholith and Manghuai rhyolites before storage in the Changning-Menglian Paleo-Tethys orogenic belt.

Multi-stage crustal melting from Late Permian back-arc extension through Middle Triassic continental collision to Late Triassic post-collisional extension in the East Kunlun Orogen

The East Kunlun Orogen is an important part of the East Tethys region and has received significant attention with regards to the evolution of the Tethys Ocean. This contribution presents geochronological, whole-rock major and trace element geochemical, and Sr-Nd-Hf isotopic data of magmatic rocks within the Kengdenongshe polymetallic deposit in the eastern part of the East Kunlun Orogen. Here, we report zircon UPb ages of ca. 257 Ma and ca. 211 Ma for granite porphyry intrusions, and ca. 240 Ma for the rhyolitic tuff. These rocks are characterized by high SiO2, variable Al2O3 and K2O, low Na2O, MgO and CaO contents, and high A/CNK ratios, which is typical of S-type granitic rocks. They exhibit large-ion lithophile element enrichment, depletion of high field strength elements, have low (La/Yb)N ratios, and negative Eu anomalies. They also display variable (87Sr/86Sr)i ratios (0.709981 to 0.720907), negative εNd (t) values (−8.7 to −5.5), and a wide (enriched) zircon εHf (t) range (−10.1 to −0.8). The geochemical and isotope data indicate magma derivation through dehydration melting of heterogeneous crustal sources including clay-poor meta-sedimentary rocks and amphibolite, which are both parts of the East Kunlun Orogen basement. These results provide evidence for the evolution of the Paleo-Tethys Ocean in the East Kunlun Orogen including Late Permian (266–255 Ma) back-arc extension, Late Permian to Middle Triassic (255–240 Ma) subduction, Middle Triassic (240–225 Ma) continental collision, and Late Triassic (< 225 Ma) post-collisional extension. This study further suggests that the 257 Ma and 211 Ma granite porphyries are related to the asthenosphere upwelling in a back-arc basin and post-collision extensional setting, respectively. The 240 Ma rhyolitic tuff is linked to anatexis associated with crustal thickening during continental collision.

Geochronological and geochemical features of the Xiaowulangou complex plutons, Xilinhot, Inner Mongolia, and their geological significance

The southern margin of the Central Asian Orogenic Belt (CAOB) is pivotal to understanding the ultimate closure process of the Palaeo‐Asian Ocean; however, controversial issues regarding the petrogenesis and tectonic setting of its Late Palaeozoic igneous rocks have caused uncertainty regarding the Late Palaeozoic oceanic and continental evolution of the area. Herein, the Xiaowulangou complex plutons near Xilinhot, Inner Mongolia, were considered as a case study for the southern margin of the CAOB, and they were analysed via multiple geological methods, including field geology, petrology, zircon U–Pb isotopic geochronology, and geochemistry to achieve greater clarity on these issues. Lithologically, the plutons consist of diorite, quartz diorite, granodiorite, and monzonitic granite. Zircon U–Pb dating gives weighted mean ages of the diorite, quartz diorite, and granodiorite plutons as 329 ± 1 (mean squared weighted deviation [MSWD] = 0.22) and 306 ± 1 (MSWD = 0.83), 310 ± 1 (MSWD = 0.23), and 328 ± 1 (MSWD = 0.40) and 300 ± 1 Ma (MSWD = 1.4), respectively, corresponding to the late Early Carboniferous to the Late Carboniferous. The diorites and the quartz diorites constitute a suite of low‐K tholeiitic calc‐alkaline I‐type granitoids. They have low rare earth element (REE) content with a flat distribution pattern lacking pronounced negative Eu anomalies (δEu = 0.74–1.06). Geochemically, they are more enriched in large‐ion lithophile elements (LILEs) such as Rb, Th, K, and Sr than in high‐field‐strength elements (HFSEs) such as Nb, Ta, Ti, and P, indicating that these rocks were formed in a subduction setting as a result of partial melting of a mantle wedge that had been metasomatized by subduction fluids. The granodiorites and monzonitic granites belong to the peraluminous and calc‐alkaline to high‐K calc‐alkaline series and feature high silicon and alkali content; low P2O5 and CaO content; enrichment in Rb, Th, K, Zr, and Hf; depletion in Nb, Ta, Sr, P, and Ti; and significant negative Eu anomalies (δEu = 0.66–0.95 and 0.06–0.46, respectively). The granodiorites and monzonitic granites show the characteristics of I‐type granite that were mainly derived from partial melting of the crust. The petrological and geochemical characteristics of the rocks indicate that the plutonic complex is a result of superposed injection of a mixture of mantle‐ and crust‐derived magmas with different degrees of evolution. This was probably triggered by underplating of mantle magmas that originated from the partial melting of a wedge mantle metasomatized by hydrous fluids from the subducted slab. The diorites and quartz diorites were produced by fractional crystallization of mantle‐derived magma. The granodiorites and monzonitic granites crystallized from magma formed by mixing of the intermediate to basic magma and crust‐derived acidic magma. Considering their petrological and geological features, the Xiaowulangou complex plutons were formed in an active continental margin setting related to the northward subduction of the Palaeo‐Asian Ocean from the Early Carboniferous to the Late Carboniferous. Furthermore, consequently, a tectonic evolution model was established from the Late Palaeozoic to the Early Mesozoic in the Xilinhot–Xi Ujimqin Banner regions based on these new data and the regional geology.

Newly discovered Neoproterozoic A‐type granite in the Altun orogenic belt: A record of the initial breakup of Rodinia

The Altun orogenic belt, located on the northern margin of the Tibetan Plateau, records the assembly and breakup of the Rodinia supercontinent. In this paper, we report the petrography, zircon U–Pb ages and Hf isotope data, and bulk geochemistry of the Hongliugou alkali feldspar granites from the Altun orogenic belt to constrain their petrogenesis and tectonic implication. Zircon U–Pb dating yielded ages of 857–851 Ma, interpreted as the emplacement ages of the granites. The granites are metaluminous; have high SiO2, K2O, and rare‐earth element (REE) contents; low CaO and P2O5 contents; high FeOt/MgO ratios; and high 10,000 × Ga/Al values. They show marked depletion in heavy REEs, enrichment in light REEs, and pronounced negative Eu anomalies. These rocks are enriched in high‐field‐strength elements, depleted in Ba, Sr, P, and Ti, and lack Nb and Ta anomalies. These petrological and geochemical characteristics are consistent with those of A‐type granites. The samples plot in the A1‐type field in a discrimination diagram for A‐type granites. Zircon εHf(t) values vary from +1.76 to +7.40 with two‐stage Hf model ages of 1.27 to 1.63 Ga, implying that the granites were derived mainly from juvenile crust. On the basis of these and previous results, we propose that the Hongliugou alkali feldspar granites formed in an intraplate rift setting related to the initial breakup of Rodinia.

Geochronology, geochemistry, and Sr–Nd–Hf isotopes of the Late Permian–Early Triassic granitoids in Eastern Kunlun Orogen, Northwest China: petrogenesis and implications for geodynamic setting

ABSTRACT The Eastern Kunlun Orogenic Belt (EKOB) in Northwest China, is an ideal area for understanding the tectonic evolution of the Palaeo-Tethys Ocean. The EKOB is marked by widespread Palaeozoic to Early Mesozoic magmatism. However, the Late Permian–Early Mesozoic tectonic evolution of the Palaeo-Tethys Ocean tectonic regime is poorly understood. Here, we report new zircon LA-ICP-MS U–Pb dating and geochemical analyses of Late Permian–Early Triassic intrusive rocks in the Xiangyanggouxi and Dageledong areas in the EKOB, Northwest China, to discuss their petrogenesis and geodynamic setting and reconstruct the tectonic evolution of Palaeo-Tethys oceanic tectonic regime. Zircon U-Pb dating results indicate that these granitoids crystallized during ca. 256–248 Ma, i.e. the Late Permian to Early Triassic. These granitoids are mainly comprised of granodiorites and monzonitic granites that possess high concentrations of SiO2 (66.81–75.98 wt.%), K2O+Na2O (6.21–7.92 wt.%), and low contents of MgO, CaO, Cr, Ni, and Mg# (<0.44). They are classified as medium- to high-K calc-alkaline and metaluminous I-type granitoids. These granitoids are rich in light rare earth elements (LREEs) and large ion lithophile elements (LILEs) and are depleted in heavy rare earth elements (HREEs) and high field strength elements (HFSEs) with arc affinity. In addition, combined with the εHf(t) values of −2.4 to +2.4 with two-stage model ages ranging from 1409 Ma to 1027 Ma, and the εNd(t) values from −3.73 to −2.95, it is suggested that the primary magma of these granitoids was derived from the partial melting of the Late Meso–Proterozoic mafic lower crust. These findings, combined with spatio-temporal distributions of regional magmatism, reveal that the Late Permian and Early Triassic granitoids formed in a continental magmatic arc setting related to the northward subduction of the Palaeo-Tethys Ocean plate beneath the EKOB-Qaidam terrane.

Synchronous A-type and adakitic granitic magmatism at ca. 2.2 Ga in the Jiao–Liao–Ji belt, North China Craton: Implications for rifting triggered by lithospheric delamination

The Jiao–Liao–Ji belt (JLJB) underwent back-arc or intra-continental rifting during the early Palaeoproterozoic but the underlying mechanism remains unclear. To address this issue, this study focuses on the petrogenesis of widespread Palaeoproterozoic granitoids on Liaodong Peninsula, China. Zircon U–Pb dating and geochemical and Hf isotopic data suggest that these granitoids were formed at ca. 2.2 Ga and they can be divided into A-type and adakitic granites. The A-type granites have relatively high SiO2, K2O, Zr, Ga, Nb and Y contents, and low CaO, MgO, Al2O3 and Sr contents. Based on these characteristics, εHf(t) values (−0.8 to +2.8) and TDM2 ages (2797–2569 Ma), the A-type granites are inferred to be derived from Neoarchaean tonalite–trondhjemite–granodiorites in a rift setting. In contrast, the coeval adakitic granites have relatively high Na2O, Al2O3 and Sr contents and high Sr/Y and LaN/YbN ratios, but low MgO, Ni, Yb and Y contents, suggesting a magma source with garnet but no plagioclase in the residue beneath thickened lower crust. Their variable εHf(t) values (−8.5 to +6.9) and TDM2 ages (3276–2305 Ma) indicate that the adakitic magmas were mainly generated by the partial melting of Meso–Neoarchaean crust. The co-existence of contemporaneous ca. 2.2 Ga adakitic and A-type granites provides evidence that the JLJB underwent regional rifting in the Palaeoproterozoic, most likely due to delamination of a thickened lithosphere, as follows. (1) In the Neoarchaean, the lower crust of the Longgang Block underwent granulite- and/or eclogite-facies metamorphism due to continuous thickening, which resulted in increasing lower crustal density. (2) The thickened lower crust became unstable and delaminated at ca. 2.2 Ga. Asthenospheric upwelling following this lithospheric delamination triggered the thinning of the overlying lithosphere. The upper crust and remnant thickened lower crust were partially melted to form the A-type and adakitic granites, respectively. The rifting likely resulted in the separation of the Longgang and Nangrim blocks, prior to their amalgamation in the late Palaeoproterozoic to form the JLJB.

Geochemical characteristics and Sr‐Nd‐Hf isotope compositions of Late Triassic post‐collisional A‐type granites in Sarudik, SW Sumatra, Indonesia

AbstractLate Triassic A‐type granites are identified in this study in Sarudik, SW Sumatra. We present new data on zircon U–Pb geochronology, whole‐rock major and trace elements and Sr‐Nd‐Hf isotope geochemistry, aiming to study their petrogenesis and tectonic implications. LA‐ICP‐MS U–Pb dating of zircon separated from one biotite monzogranite sample yields a concordia age of 222.6 ±1.0 Ma, indicating a Late Triassic magmatic event. The studied granites are classified as weakly peralumious, high‐K calc‐alkaline granites. They exhibit high SiO2, K2O + Na2O, FeO/(FeO + MgO) and Ga/Al ratios and low Al2O3, CaO, MgO, P2O5 and TiO2 contents, with enrichment of Rb, Th and U and depletion of Ba, Sr, P and Eu, showing the features of A‐type granites. The granites have zircon εHf(t) values from −4.6 to −0.4 and whole‐rock εNd(t) values from −5.51 to −4.98, with Mesoproterozoic TDM2 ages (1278–1544 Ma) for both Hf and Nd isotopes. Geochemical and isotopic data suggest that the source of these A‐type granites is the Mesoproterozoic continental crust, without significant incorporation of mantle‐derived component, and their formation is controlled by subsequent fractional crystallization. The Sarudik A‐type granites are further assigned to A2‐type formed in post‐collisional environment. Combined with previous knowledge on the western SE Asia tectonic evolution, we conclude that the formation of the Late Triassic A‐type granites is related to the post‐collisional extension induced by the crustal thickening, gravitational collapse, and asthenosphere upwelling following the collision between the Sibumasu and the East Malaya Block.

Characterization of Portland Cement Incorporated with FNS

The potential use of ferronickel slag (FNS) as supplementary cementitious material has been widely researched in recent years. Although much research was carried out on utilizing FNS as a binder, its advantages and disadvantages are still not clear. To properly use FNS as a cement replacement, this paper summarizes the following. (1) Changes expected on the oxide composition of FNS powder are due to the forming ores, fluxing stone, and cooling method. (2) The decreasing of the hydration heat evolution rate was detected by hydration heat evolution test and this is due to the low content of CaO and Al2O3 component in FNS. (3) It was found that the incorporation of FNS forms a dense pore structure more than cement mix and this is due to the secondary hydration reactions. (4) Hydration characteristics of FNS were assessed by pozzolanic reactions unexpectedly detected and incorporation of FNS creates C‐S‐H gel and hydrotalcite. (5) The development of strength was tested by compressive strength, splitting tensile strength, and flexural strength. From the results, the reduction of compressive strength was detected at an early age but substantially increasing at the long‐term curing ages. However, splitting tensile strength and flexural strength of concrete have shown various trends. (6) There is an improvement in the resistance to chloride penetration and sulfate attack while susceptible to carbonation. This is induced by the lowered pH in pore solution due to the reduction of Ca(OH)2 by substituting FNS binder. Finally, (8) ternary blended mixtures with conventional cementitious materials are an option to properly use FNS as a binder.