High SiO2 Contents Research Articles

A geochronological and geochemical study on the granodiorite porphyry and its implication for the mineralization in the Dayaoshan metallogenic belt, Southeastern China

A systematic study combining U-Pb zircon dating, lithogeochemical and Sr–Nd isotopic analyses was carried out upon the Xinping granodiorite porphyry in the Dayaoshan metallogenic belt to understand its petrogenesis and tectonic significance. LA-ICP-MS U–Pb zircon dating yielded a 442.7 ± 5.8 Ma age, indicating that the granodiorite porphyry was emplaced during the Llandovery Silurian of the Early Paleozoic. The granodiorite porphyry shares the same geochemical characteristics such as Eu negative anomaly as other syn-tectonic granite plutons in the region, including the granodiorite porphyry in Dawangding and granite porphyries in the Dali Cu–Mo deposit and Longtoushang old deposit, indicating a similar magma evolution process. The Xinping granodiorite porphyry has high contents of SiO2 (67.871.8%) and K2O (1.78–3.42%) and is metaluminous–peraluminous with A/CNK ratios ranging from 0.97 to 1.06, indicative of high-potassium calc-alkaline to calc-alkaline affinity. It is a I-type granite enriched in large ion lithophile elements Rb, Sr, while depleted in Ba and high field-strength element Nb. Tectonically, a collision between the Yunkai Block from the south and the Guangxi Yunnan-North Vietnam Block from the north during the Early Paleozoic was followed by uplifting of the Dayaoshan terrane. The Xinping granodiorite porphyry was likely emplaced during the collision. Sr–Nd isotopic analyses show that the granodiorite porphyry has initial 87Sr/86Sr ratios (Isr) of 0.7080–0.7104, eNd(t) range from − 0.08 to − 4.09, and t2DM between 1.19 and 1.51 Ga, well within the north-east low-value zone of the Cathaysia block, indicating a Paleoproterozoic Cathaysia basement source and an involvement of under plating mantle magma. Field observations, geochronological data, and 3D spatial distribution all lead to the conclusion that the Early Paleozoic Xinping granodiorite porphyry does not have any metallogenic and temporal relationships with the Xinping gold deposit (which has a Jurassic-Early Cretaceous age based on previous studies) but a close metallogenic relation to W–Mo mineralization.

Petrogenesis and tectonic significance of Late Triassic Baishiya granodiorite porphyries in the Dulan area, eastern segment of the East Kunlun Orogenic Belt, China

The timing of closing of the A'nyemaqen Ocean—the north branch of the Palaeo‐Tethys Ocean—and the subsequent continental collision remain controversial. In this study, detailed geochronological and geochemical analyses of the Baishiya granodiorite porphyries in the Dulan area [eastern segment of the East Kunlun Orogen Belt (EKOB)] were conducted. The LA–ICP–MS zircon U–Pb dating analysis revealed that the Baishiya granodiorite porphyries were emplaced during the Late Triassic (~223 Ma) and possess adakitic features, including relatively high SiO2 (67.2–69.0 wt%), Al2O3 (15.2–15.9 wt%), and Sr (416–540 ppm) contents, low Y (10.5–12.3 ppm) and Yb (1.03–1.38 ppm) contents, and high Sr/Y and La/Yb ratios. They belong to the high‐K calc‐alkaline series and show significant light rare‐earth element enrichment, minor Eu anomalies, HFSE depletion, and LILE enrichment. The porphyries record a narrow range of (87Sr/86Sr)i ratios (0.709067–0.709920) and ɛNd(t) values (−6.84 to −5.27) with two‐stage model ages (TDM2) ranging from 1,426 to 1,554 Ma. These geochemical features imply that the Baishiya granodiorite porphyries originated from the partial melting of the thickened Mesoproterozoic lower crust by mixing with minor mantle‐derived material. Late Triassic adakitic magmatism in the eastern segment of the EKOB formed in a post‐collisional extension setting due to the closing of the A'nyemaqen Ocean since Early Triassic.

Electrical Conductivity of the Slag Melts from the Production of Germanium Concentrates

The pyrometallurgical technology of producing germanium concentrates from the raw materials taken from brown coal deposits (coal, mudstones, siltstones) is accompanied by the formation of silicate slag melts, which concentrate the mineral component of the raw materials (reaching 60% wt %). Obviously, the energy indicators of technology are substantially determined by the physicochemical properties of slag melts. These include electrical conductivity λ, which reflects the structure of silicate melts. The compositions of the slags from processing carbonaceous raw materials differ significantly from nonferrous and ferrous metallurgy slags: they contain high contents of SiO2 (up to 50–55%), Al2O3 (up to 20–22%), and K2O and Na2O (up to 5–6%). In addition, noticeable amounts of sulfide sulfur (up to 3%) and microimpurities of nonferrous metals and rare elements (up to 5%) are present in the slags. The differences between the compositions of the slag melts of germanium production and the slags of the general metallurgy affect their properties and require special-purpose studies. Industrial samples of cyclone melting and electric melting slags are studied. Semisynthetic samples prepared from industrial samples by adding SiO2 and CaO are used to determine the influence of the slag composition on λ. A standard compensation method is used to measure the resistance of the melt with an ac bridge at a frequency of 3.5 kHz. The cell consists of a melt in an alundum crucible with immersed molybdenum electrodes. The melt temperature range is 1100–1550°C. The values ​​of λ of the melts are found to be in the range from 0.01 to 0.30 S/cm and to depend substantially on the basicity (i.e., the ratio of the sum of the CaO and MgO contents to SiO2) and the Al2O3 content. The temperature dependences of λ are shown to be exponential. In the general case, λ of the melts under study is much higher than that characteristic of, e.g., blast-furnace melting at the same basicity. The results obtained are useful for predicting the structure of melts.

Mineralogical study of archaeological copper slags found in the area of Krushevets Village, SE Bulgaria

In this article, we present the results of our study on archaeological slags found near the village of Krushevets, Southeast Bulgaria. Chemical analyses of the slags show a high Fe2O3 (40.11–54.57%) and SiO2 (29.32–42.28%) content, increased CaO content (3.01–6.51%), as well as very low quantity of SO3 (from 0.20% to 0.52%) and P2O5 (between 0.23% and 0.30%). The unbound residual copper in the samples is in an amount of 0.41% to 1.07%. The main phases composition of the slags are as follows: fayalite-type silicate phases with impurities, kirschsteinite and laihunite; pyroxenes of the augite-type and amorphous hosted glass; iron-oxide phases (magnetite and maghemite); and copper-containing phases (drops of unbound copper, relicts of ore minerals such as bornite, chalcopyrite), as well as newly formed phases, such as chalcocite, and copper-containing spherical aggregates. The studied samples are a by-product of copper extraction metallurgical activity. The raw material used was of copper-sulfide type with impurities of manganese-, calcium-, magnesium- and aluminium-containing minerals.

Geochronology, geochemistry, mineralogy and metallogenic implications of the Zhaojinggou Nb-Ta deposit in the northern margin of the North China Craton, China

The large Zhaojinggou Nb-Ta deposit is located in the northern margin of the North China Craton (NCC), Inner Mongolia, China. The deposit is mainly hosted in the mineralized dikes around the Hutoushan pluton and the residual pegmatite shell at the top of the pluton. Samples from the pluton and the mineralized dikes are characterized by high contents of SiO2 (73.3%–84.3%), total alkalis (5.24%–9.60%) and Al2O3 (7.94%–13.8%), and moderate A/CNK values (with an average of 1.04) indicating a weakly peraluminous affinity. The trace element patterns are characterized by Rb, Nb, Ta, Zr, and Hf enrichment and markedly negative Ba, Sr, P, Eu, and Ti anomalies. Zircon U-Pb dating suggests that the emplacement of the pluton and the Nb-Ta mineralization occurred coevally in the Early Cretaceous (126 ± 1 Ma and 127 ± 2 Ma, respectively). Variations in both bulk-rock geochemistry (K/Rb, Zr/Hf, Nb/Ta) and mineral composition (mica and columbite) consistently unveil a magmatic evolutionary trend from the Hutoushan alkali-feldspar granite, through the Hutoushan pegmatite shell, to the mineralized dikes. Typical A-type characteristics of the granite and ancient Hf isotopic features [εHf(t) ranging from −6.80 to −12.95, and crust model ages from 1.61 to 2.00 Ga] indicate that the parental magma was derived from the partial melting of Palaeoproterozoic crust with insignificant mantle material involved. Considering the significantly higher bulk contents of Nb, Ta, and F in the pegmatite shell and the mineralized dikes than that in the alkali-feldspar granite, as well as the similar composition in the biotite from the pegmatite shell and the alkali-feldspar granite, we propose that a residual Nb-Ta-enriched brine-melt phase segregated from the crystal mush at the late stage of crystallization. The progressive concentration of F in the melt was conducive to the solubility of Nb and Ta in granitic melts and decreased the viscosity by depolymerizing the melt, and thus contributed to the high magma differentiation and Nb-Ta concentration. The post-magmatic fluid triggered the fluid-rock interaction, resulting in the extensive albitization, M-type “tetrad effect”, extremely low Nb/Ta ratio (<5), and further mineralization in the mineralized dikes.

Geochemistry of the Villismán granite, associated aplite-pegmatites and surrounding Li-pegmatites, Sierra de Ancasti, Argentina

The Villismán pegmatite group belonging to the Ancasti district of the Pampean Pegmatite Province is geologically formed by banded schists of the Ancasti Formation which are intruded by the homonymous granitic stock and Li-pegmatites. It is located in the northern sector of the Sierra de Ancasti, Catamarca province, Argentina. The Villismán stock -VG- is a small, sub-rounded in shape two-mica-syenogranite. The VG hosts felsic aplitic and pegmatitic dykes -FDVG- with muscovite, black-tourmaline (schorl) ± garnet as main accessory minerals. The Li-pegmatites contain giant crystals of spodumene and are classified as of the Rare-Element class (REL) and REL-Li subclass pegmatites and belong to the LCT (Li–Cs–Ta) pegmatite family. They are more or less symmetrically zoned with outward zones composed of felsic aplite and coarse-grained to very coarse-grained granite -OZLiP-. The minerals of OZLiP are quartz, feldspars (secondary albite ‘cleavelandite’ predominant over K-feldspar), muscovite and scarce black-tourmaline (schorl), garnet and F-apatite. The VG, FDVG and OZLiP have high and similar SiO2 concentrations (72–78 wt %). They are peraluminous (ASIVG 1.10–1.16; ASIFDVG 1.23–1.77, ASIOZLiP 1.00–1.14). The VG has subalkaline-calc alkaline character with K2O > Na2O. Ferromagnesian elements (included Ti) and CaO have low concentrations in VG and the FeOt/FeOt + MgO ratio is low (0.80–0.82) classifying it as magnesian granite. High Rb/Sr (FDVG ~16; OZLiP ~19) and Rb/Ba (FDVG ~41; OZLiP ~ 7) and low K/Rb (FDVG ~107; OZLiP ~56) ratios clearly indicate that aplites and pegmatites are geochemically more evolved than the Villismán Granite (Rb/SrVG ~ 3; Rb/BaVG ~ 0.8; K/RbVG ~ 161). The Zr-saturation temperature in the granites, as expected, is higher than in the dykes and the outward zones of the Li-pegmatites. The VG is a post-orogenic granite developed in the easternmost sector of the Ordovician Famatinian active arc. All geological, mineralogical and geochemical features of the VG are comparable to typical S-type granites, probably originated from partial melting of the metasedimentary rocks of the Ancasti Formation. FDVG could have been formed by fractional crystallization from the VG parental-magma.

Geochemistry and U–Pb (SHRIMP) geochronology of Grupelli Granite: New constraints on the cessation of felsic magmatism in the Pelotas Batholith, Dom Feliciano Belt

The Pelotas Batholith forms the eastern portion of the Neoproterozoic Dom Feliciano Belt and records the final stages of the Neoproterozoic Brazilian–Pan-African orogeny. This granite-dominated belt experienced a complex tectonomagmatic evolution, yet constraints on the nature, and especially, the timing of the different magmatic stages are still scarce. This study provides new geochemical and geochronological constraints on the Grupelli Granite, a post-deformational pluton located in the rural district of Quilombo, Pelotas, RS. This granite crops out as a series of sub-kilometric solid bodies along a NE–oriented fault zone, intruding the Pinheiro Machado Complex that dominates the central and southeastern portion of the Pelotas Batholith. The studied granite is widely used as an ornamental rock due to its extremely leucocratic and isotropic appearance. The Grupelli Granite is homogeneous, relatively undeformed, inequigranular and typically medium-to coarse-grained (1–5 mm), with porphyritic and hypidiomorphic textures. Based on modal mineralogy the rock is a monzogranite with 40–50% quartz, 19–25% K-feldspar, and 15% oligoclase, 3–5% biotite, 2–3% magnetite and ilmenite, and accessory chlorite, zircon, apatite, chalcopyrite, and pyrite. Geochemically, the Grupelli Granite is characterized by high SiO2 (74–77 wt%) and K2O (5.08–5.65 wt%) contents combined with low FeOt (1.71–1.93 wt%), MgO and TiO2 (<0.2 wt%) concentrations. This highly evolved granite has a high-K calc-alkaline affinity, is weakly peraluminous, with I-type fingerprints. The combined data are consistent with formation in a post-tectonic environment by anatexis of mainly calk-alkaline sources, with a potential minor contribution of a metapelitic source. The low Sr-contents and concomitant high Ba/Sr ratios likely reflect plagioclase fractionation, while ilmenite fractionation may account for the pronounced negative Nb, Ta, and Ti anomalies. Although the rare earth element (REE) and other trace element patterns tend to parallel the patterns in the ca. 600 Ma Dom Feliciano Suite and the Cerro Grande Suite magmatism, the Grupelli Granite presents significantly lower heavy REE (HREE) concentrations and a smaller negative Eu anomaly. The HREE depletion can be attributed to retention of garnet in the source. These geochemical characteristics distinguish it from the earlier magmatic pulses in the Pelotas Batholith. The Grupelli Granite yielded a crystallization age of 578 ± 3.9 Ma (U–Pb zircon SHRIMP), and is thus younger than the ca. 600 Ma Dom Feliciano and Cerro Grande suites. This crystallization age places new constraints on the felsic post-collisional magmatism during the final stages of the evolution of Pelotas Batholith.

Long-Lasting (65 Ma) Regionally Contrasting Late- to Post-Orogenic Variscan Mantle-derived Potassic Magmatism in the Bohemian Massif

Abstract The orogenic development after the continental collision between Laurussia and Gondwana, led to two contrasting associations of mantle-derived magmatic rocks on the territory of the Bohemian Massif: (i) a 340–310 Ma lamprophyre-lamproite orogenic association; and (ii) a 300–275 Ma lamprophyre association of anorogenic affinity. Major types of potassic mantle-derived magmatic rocks recognized in the orogenic and anorogenic associations include: (i) calc-alkaline to alkaline lamprophyres; (ii) alkaline ‘orthopyroxene minettes’ and geochemically related rocks grouped here under the new term lampyrite; and (iii) peralkaline lamproites. These three types significantly differ with respect to mineral, whole-rock and Sr–Nd–Pb–Li isotope composition and spatial distribution. The calc-alkaline lamprophyres occur throughout the entire Saxo-Thuringian and Moldanubian zones, whereas the different types of malte-derived potassic rocks are spatially restricted to particular zones. Rocks of the Carboniferous lamprophyre-lamproite orogenic association are characterized by variable negative εNd(i) and variably radiogenic Sr(i), whereas the rocks of the Permian lamprophyre association of anorogenic affinity are characterized by positive εNd(i) and relatively young depleted-mantle Nd-model ages reflecting increasing input from upwelling asthenospheric mantle. The small variation in the Pb isotopic composition of post-collisional potassic mantle-derived magmatic rocks (of both the orogenic and anorogenic series) implies that the Pb budget of the mantle beneath the Bohemian Massif is dominated by the same crust-derived material, which itself may include material derived from several sources. The source rocks of ‘orthopyroxene minettes’ are characterized by isotopically light (‘eclogitic’) Li and strongly radiogenic (crustal) Sr and may have been metasomatized by high-pressure fluids along the edge of a subduction zone. In contrast, the strongly Al2O3 and CaO depleted mantle source of the lamproites is characterized by isotopically heavy Li and high SiO2 and extreme K2O contents. This mantle source may have been metasomatized predominantly by melts. The mantle source of the lamprophyres may have undergone metasomatism by both fluids and melts.

Sn recovery from a tin-bearing middling with a high iron content and the transformation behaviours of the associated As, Pb, and Zn

A tin-bearing middling with high Fe and low SiO2 contents is generated from the beneficiation of tin-bearing tailings. The middling is composed of valuable Sn and Fe metals and harmful Pb, Zn, and As elements, which can cause severe economic and environmental issues if left on land for extended periods. This study proposed a new two-step process for the treatment of the middling, which includes oxidising roasting followed by sulfurization roasting. The results demonstrate that Sn, Pb, Zn, and As were volatilised efficiently and concentrated in the collected dust while concentrated Fe remained in the roasted residue. During the sulfurization roasting process, CaSO4 that originated from the middling played a major role in Sn sulfurization and volatilisation through its transformation to SO2 (g). Furthermore, CO2 (g) positively affected separation of Sn and As from FeSn and FeAs alloys, respectively, via the selective oxidation of the Fe component in the alloy phases. Under optimal conditions, the Sn recovery reached 97.5%, and the residual contents of As, Pb, and Zn decreased to 0.055, 0.013, and 0.13 wt%, respectively. This study aids in the resource utilisation of tin-bearing middling and is of substantial significance for the quantitative reduction of tin-bearing tailings.

Petrogenesis and tectonic setting of the Chaheilingashun pluton, North Alxa Block, NW China: constraints from whole-rock geochemistry, zircon U–Pb ages, and Hf isotope compositions

To better constrain the petrogenesis and tectonic setting of the Chaheilingashun pluton in the southern Ya-Gan Fault, North Alxa Block, NW China, this study presents new zircon U–Pb ages, whole-rock geochemistry, and Hf isotopes of diorites from the Chaheilingashun pluton. The Chaheilingashun pluton is composed of medium- to coarse-grained monzonitic diorite, with moderate to high SiO2 contents (58.22–62.77 wt.%), moderate total alkali contents (Na2O + K2O, 5.72–7.66 wt.%), and high Al2O3 contents (14.26–17.69 wt.%), which indicate that the diorite exhibits calc-alkaline to alkaline and metaluminous to peraluminous series. The correlations of SiO2 with oxides and the right-dipping oblique trends of rare earth elements (REEs) demonstrate that the magma experienced fractional crystallization. In particularly, the correlations of Rb with Ba and Sr, and the weak negative Eu anomalies indicate that the plagioclase has undergone fractional crystallization. In addition, this paper has shown that both fractional crystallization and partial melting also contributed to the magmatic process through the Eu anomalies and La/Sm-La diagram. The positive eHf(t) values (2.2–4.6) and low Mg#, Cr, and Ni indicate that diorite was generated from the partial melting of juvenile mafic crust. Together with previous results, the diorites are inferred to have formed in an post-collisional extensional environment. The zircon U–Pb age of diorite from the Chaheilingashun pluton is dated at 289.3 Ma, suggesting that the final closure time of the Paleo-Asian Ocean was might before 289.3 ± 2.3 Ma.

Middle Cambrian granites in the Dunhuang Block (NW China) mark the early subduction of the southernmost Paleo-Asian Ocean

The formation and evolution of the Central Asian Orogenic Belt (CAOB) were closely associated with the opening and closure of the so-called “Paleo-Asian Ocean” (PAO). The subduction of the southern PAO is expected to have resulted in widespread Paleozoic arc magmatism in the southernmost CAOB. However, the precise location and timing of such subduction remain uncertain. The Dunhuang Block (DHB) in the southernmost CAOB is thought to have recorded such subduction. In this contribution, we report the results of the zircon U–Pb ages, Hf isotopes, and whole-rock geochemical data for the Lianghu, Dapokouzi, and Xiaowan plutons in the northeastern DHB, NW China. Zircon U–Pb dating reveals that these plutons formed at ca. 510 Ma (the Middle Cambrian) and may represent the oldest arc-related magmatism in the DHB. Geochemically, the Dapokouzi pluton is characterized by high SiO2 (70.7–71.2 wt%), Na2O (5.11–5.26 wt%), Al2O3 (15.5–15.6 wt%), and Sr (730–733 ppm) contents, high Sr/Y (380–398) ratios, moderate Mg# (49–50) values, low MgO (0.61 wt%), K2O (2.00–2.01 wt%) and Y (1.84–1.93 ppm) contents, and weakly positive Eu (1.39–1.44) anomalies, indicating geochemical affinities of adakitic rocks. They have positive εHf(t) values (+11.2 to +13.9) close to the depleted mantle line and young two-stage model ages (TDM2 = 571–742 Ma). All the geochemical characteristics show that the Dapokouzi pluton was derived from the remelting of juvenile crust with addition of minor metasomatized mantle-derived materials and a residue phase dominated by garnet-bearing amphibolite. Similarly, the Lianghu and Xiaowan plutons have high SiO2 (70.2–74.4 wt%) and Al2O3 (12.8–14.3 wt%), low MgO (0.61–1.01 wt%) with Mg# values of 35–43 and K2O (0.43–1.55 wt%) contents. Compared to the Dapokouzi pluton, they exhibit low Sr (121–155 ppm) and Y (15.3–23.1 ppm) contents, low Sr/Y (5.25–9.54) ratios and Cr-Ni-Co concentrations, and pronouncedly positive εHf(t) values (+11.0 to +14.7), indicating that the magmas originated from the remelting of juvenile lower crust followed by significant fractional crystallization at relatively shallow crustal depths. Data from this and previous studies convincingly suggest the DHB was located in a thickened continental arc setting during the early Paleozoic, probably related to the early subduction of the PAO lithosphere. Crustal thickening, as indicated by the geochemical signature of the Dapokouzi pluton, was most likely associated with the underplating of mantle-derived mafic magmas during the slab subduction. This study therefore highlights that the subduction of the southern PAO might have initiated prior to 510 Ma, possibly dating back to the early Cambrian.

Paving way for fabrication of silica-based single -frequency seed laser: Ultrahighly Yb-doped optical fibers via sol-gel method combined with silica tube inner wall coating and fusion-tapering technique

A method based on sol-gel preparation combined with silica tube inner wall coating and fusion-tapering technique for fabrication of ultrahighly rare-earth-doped fibers without fluorescent quenching is provided. Ultrahighly Yb-doped high SiO2 content glass fiber is developed and is easily spliced to commercial fiber-components. A ~ 1.03 μm laser with 70 dB-SNR and 0.2 nm-linewidth is achieved. The problem of low dissolution rate to rare-earth ions in silica fibers and the splicing problem between soft glass fibers and commercial fiber components have been overcome, indicating the method has potential in fabrication of short-cavity high-gain silica fiber which is applicable to single-frequency seed source. The method is worth exploring in that the core can extend to any heavily rare-earth-doped system as long as it can be realized in the sol form with good dispersion, therefore paving way for fabrication of silica-based single-frequency seed laser.

Contrasting composition of two biotite generations in the Lizhuang rare‐earth element deposit, Sichuan Province, Southwestern China

Biotite is an important silicate mineral that can be used to decipher the physicochemical attributes of magmatic or hydrothermal systems. The Lizhuang rare‐earth element (REE) deposit in Sichuan Province, Southwestern China, formed from continuous magmatic‐hydrothermal processes is related to a Cenozoic carbonatite–syenite complex. Biotites are abundant in this deposit, which can be divided into two generations: generation I in intergrown with alkaline feldspar and aegirine‐augite and generation II in association with bastnäsite‐(Ce). We investigated chemical composition of the two biotite generations using electron‐microprobe(EMPA) and laser ablation–inductively coupled plasma–mass spectrometer (LA–ICP–MS) analyses to understand the development of REE mineralization. Generation I biotite has relatively high Al2O3 (10.2–12.4 wt%), TiO2 (0.49–1.85 wt%), and FeOtot (12.2–15.9 wt%), but low SiO2 (40.0–42.5 wt%) contents compared to generation II counterpart. These two generations of biotite also differ in some key trace elements. Specifically, generation I biotite has much higher concentrations of Sr (up to 234 ppm) and Ba (up to 20,796 ppm), but lower levels of Li (47.5–126 ppm) with respect to its generation II counterpart. When comparing Lizhuang biotites with those of other barren carbonatite complexes, we identified an unusual compositional trend in the generation II biotites termed as fluorphlogopite trend. This trend is marked by the continuous increase in the Mg content towards mineralization and, therefore, can serve as a diagnostic attribute in the determination of mineralized carbonatite complexes. Fluorine in biotite is an important parameter that can be used as a vector for REE exploration, because the generation II biotite presents much higher fluorine contents (2.20–4.06 wt%) than its generation I counterpart (0.87–1.59 wt%). The compositional data of the two biotite generations indicate a depletion of Fe and a progressive enrichment in Mg and F in the ore‐forming system during its evolutionary process. Physicochemical parameters estimated by biotite composition suggest that there is a trend of strongly decreasing temperature from the crystallization of generation I to generation II biotite. It is therefore concluded that temperature is a major factor favourable for REE mineralization in the Lizhuang deposit, particularly given related experimental studies. Taken together, we propose that biotite composition could serve as a proxy for REE mineralization processes and as a reliable index for REE routine exploration in a carbonatite‐related setting.

Geochemistry of Garga-Sarali intrusive granitoids (central domain of the central African fold belt in Cameroon): petrological implication

The Garga-Sarali granitoids outcrop in form of large slabs and undistorted large blocks, into a schisto-gneissic basement. These rocks contain mainly muscovite and microcline, followed by K-feldspar, quartz, biotite, pyroxene, zircon and oxides, with coarse-grained to fine-grained textures. Geochemical analysis show that it belongs to differentiated rocks group (granodiorite-granite) with high SiO2 (up to 72 wt%) contents. Their genesis was made from a process of partial melting and fractional crystallization. These rocks are classified as belonging to I- and S-Type, meta-peraluminous, shoshonitic granites; belonging to the domain of volcanic arcs. The rare earth elements patterns suggest a source enriched of incompatible elements. The Nb-Ta and Ti negative anomalies from the multi-element patterns are characteristics of the subduction domains.

Phanerozoic magma underplating associated with remelting of the lower crust beneath the Cathaysia Block: Evidence from zircon U[sbnd]Pb ages and Hf[sbnd]O isotopes of granulite xenoliths from Daoxian, South China

Widespread Mesozoic granitoids in the Cathaysia Block of South China are associated with intensive reworking of the lower crust as a result of magma underplating. This inference is based mainly on studies of mafic igneous rocks, whereas there is little evidence from lower-crustal rocks. Lower-crustal xenoliths in Mesozoic basalts in the Daoxian region within the Cathaysia Block might record information on the relationship between magma underplating and remelting of the pre-existing crust beneath the block. The xenoliths are mainly mafic granulites, with minor felsic granulites. The mafic granulites have low SiO2 contents (47.22–49.46 wt%) and high Mg# values (77.8–82.4), suggesting that their protoliths were derived from a mantle source. The felsic granulite xenoliths have high SiO2 (69.56–70.27 wt%) and low MgO (1.63–2.50 wt%) contents, and zircons in these xenoliths yield negative εHf(t) values (−6.1 to −12.6) and high δ18O values (6.8–7.6‰), consistent with a crustal source. Both mafic and felsic granulite xenoliths record magmatic (226–218 Ma) and metamorphic (218–193 Ma) events, suggesting a genetic link between mafic and felsic rocks in the lower crust. We propose that the magma underplating was responsible for the origin of the mafic granulites and partial melting of pre-existing lower crust, as recorded by the felsic xenoliths. The granulite xenoliths also contain abundant inherited zircons that formed during the Archean–Neoproterozoic (2584–659 Ma), early Paleozoic (peaking at ca. 425 Ma), and late Paleozoic (peaking at ca. 261 Ma). Zircons from the Daoxian granulite xenoliths have distinct HfO isotopic compositions that record the multistage evolution of the lower crust beneath the Cathaysia Block. This evolution involved the accretion of juvenile crust during the late Archean (εHf(t) = +4.2 to +4.6) and late Paleozoic (εHf(t) = +1.3 to +5.3; δ18O = 5.8–6.2‰), crustal reworking during the Neoproterozoic (εHf(t) = −7.5 to −11.8; δ18O = 5.1–9.5‰) and early Paleozoic (εHf(t) = −0.5 to −2.2; δ18O = 7.3–7.5‰), and crustal accretion with significant reworking during the early Mesozoic (εHf(t) = −19.2 to +5.9; δ18O = 6.8–7.6‰). The UPb ages and HfO isotopic data of zircons from the Daoxian granulite xenoliths are consistent with the distribution of Phanerozoic igneous rocks in the Cathaysia Block. These data support the inference that Mesozoic magma underplating triggered the remelting of pre-existing crustal materials and produced extensive granitoid magmatism.

Geochemical Approach and Industrial Utilization of Some Marble Bodies from Ubo River Area and Environs, Southwestern Nigeria

Marble bodies occur in Ubo River Area as lenses of rocks. Seven (07) marble samples were obtained, analyzed and subjected to X-Ray Flourescence (XRF) analysis to determine both the major and trace elemental composition of the samples. The analysis revealed high CaO values (52.23-58.10 wt. %) and moderate values for SiO2 (7.50-10.43wt. %), fairly low values for Al2O3 (2.30 – 4.21 wt. %), Fe2O3 (2.62 – 5.15 wt. %), MgO (0.42 – 0.7 wt. %), MnO (0.01 – 0.06 wt. %), K2O (0.32 – 1.55 wt. %) and Na2O (0.01 – 0.03 wt. %), respectively. Variation plots involving Na2O/Al2O3 vs K2O/Al2O3 reveal sedimentary progenitors for the rocks. The fairly high SiO2 and low K2O content is an indication of the environment of deposition and may have been in a shallow marine environment with fair input of classic sediments into the system. The relatively high CaO content, moderate SiO2content and fairly low Al2O3 and Fe2O3 values indicates a fair degree of purity of the parent rock, hence its suitability as a raw material in the industrial sector.&#x0D; Keywords: Clastic, Deposition, Environment, Progenitor, Marble, Chemical

Geochronology, geochemistry, and Hf isotopic compositions of early Permian syenogranite and diabase from the northern Great Xing’an Range, northeastern China: petrogenesis and tectonic implications

Geodynamic evolution in the late Paleozoic is significant for understanding the final amalgamation of the Central Asian Orogenic Belt (CAOB). No consensus has yet been reached regarding the late Paleozoic geodynamic evolution of the northern Great Xing’an Range (GXR) in northeastern China, the eastern CAOB. Furthermore, late Paleozoic syenogranite–diabase dyke association is present in the Xiaokele area in northern GXR. It provides an important opportunity to understand the nature of magmatism and the geodynamic evolution during this period. This paper presents new zircon U–Pb ages, zircon Hf isotopic compositions, and geochemical data of whole rocks for Xiaokele syenogranite and diabase. Zircon U–Pb dating suggests that the Xiaokele syenogranite (292.5 ± 0.9 Ma) and diabase (298.3 ± 1.5 Ma) were emplaced during the early Permian. The Xiaokele syenogranites have high SiO2 contents, low MgO contents, and enriched zircon εHf(t) values, suggesting that their primary magma was generated by the partial melting of the juvenile crustal material. The Xiaokele diabases have low SiO2 contents, high MgO contents, are enriched in large-ion lithophile elements, depleted in high-field-strength elements, and exhibit enriched zircon εHf(t) values. They derived from a lithospheric mantle source that had previously been metasomatized by slab-derived fluids. Combined with previous research results, we believe that the continent–continent collision between the Xing’an and Songliao blocks occurred during the late early Carboniferous – early late Carboniferous (330–310 Ma), and the two blocks were transformed into a post-collisional extensional setting during the latest Carboniferous – early Permian.

Effect the silica sand percentage as subtitution of fine agregate on the concrete compressive strength

This study uses silica sand, which has a high SiO2 content and micron size as a substitute for normal sand with control specimens with compressive strength of fc ′ 45 MPa. Two types of silica sand gradations were used, namely 80-100 mesh(0.177 mm – 0.149 mm) in size and 325 mesh (0.044 mm) in size from Bangka as the fine aggregate. There were 45 cylindrical specimens sized 15 cm in diameter, 30 cm in height, and age of7, 14, and 28 days. The tests carried out were absorption test and compressive strength test based on SNI 1974: 2011, which explained the testing method of the compressive strength of concrete with cylindrical specimens. Based on the test results, the optimum compressive strength was 53.07 MPa in the specimen with a composition of 50% sized 80-100 mesh (0.177 mm – 0.149 mm) (+) 50% sized 325 mesh (0.044 mm) silica sand, which can increase 4.12% of the compressive strength from normal concrete. On the other hand, the lowest compressive strength was obtained in a specimen with a composition of 25% sized 80-100 mesh (0.177 mm – 0.149 mm) (+) 25% size325 mesh (0.044 mm) silica sand, which was 48.43 MPa at 28 days.

Late Paleoproterozoic crustal evolution in the Daqingshan area: Evidences from adakitic and A-type granitoids in the Guyang Changshengqu goldfield, Khondalite Belt, North China Craton

Granitic magmatism related to the collisional orogenic belt provides important information for the evolution of continental crust. We performed petrological, geochemical and zircon U-Pb-Hf isotopic studies on four granitoid samples from the Guyang Changshengqu goldfield, Daqingshan area, Khondalite Belt, North China Craton. The zircon U-Pb dating results indicate that the granitoids emplaced at 1950 ± 11 Ma, 1935 ± 12 Ma, 1846 ± 11 Ma, and 1812 ± 8.6 Ma, represent two periodic granitic magmatism in the Daqingshan area. The 1.95 and 1.93 Ga granites exhibit high SiO2, K2O, and Na2O contents with high Sr/Y and (La/Yb)N ratios, but low MgO, Cr, and Ni contents, indicating that they were produced by the partial melting of a thickened lower crust under relatively high-pressure conditions. The granites show negative-dominated zircon εHf(t) values (−5.7 to 1.9), and their zircon TDM2(Hf) values range between 2.9 and 2.5 Ga, indicating an ancient crust source with minor juvenile crustal material involved. The 1.85 and 1.81 Ga quartz monzonites exhibit high SiO2, K2O, Na2O, Zr, Nb, Ce, and Y but low MgO, Cr, and Ni contents, with high Ga/Al and FeOt/(FeOt + MgO) ratios, indicating an A-type granite affinity. The whole-rock geochemistry suggests that they were formed by dehydration re-melting of TTG and quartz diorite at high temperatures and shallow depths. The quartz monzonites show homogeneous εHf(t) values (−10.6 to −6.1) and the zircon TDM2(Hf) values range between 3.0 and 2.8 Ga, suggesting that they were derived from a Neoarchean ancient crust. The 1.95–1.93 Ga adakitic magmatism is associated with the 1.93–1.92 Ga mafic magmatism and UHT metamorphic in the eastern part of the Khondalite Belt; this suggests a tectonic transition from collisional compression to post-collisional extension. The 1.85–1.81 Ga A-type granitic magmatism indicates evident continental crust thinning and asthenospheric upwelling. The two unrelated magmatism are possibly induced by two collisional events from the Khondalite Belt and the Trans-North China Orogen, respectively. The collision of the western and eastern blocks at ca. 1.85 Ga may have played an important role in the A-type quartz monzonites origin and influenced the crustal evolution as far as the Daqingshan area in the Khondalite Belt.

Geochronological, Geochemical and Sr-Nd-Hf Isotopic Studies of the A-type Granites and Adakitic Granodiorites in Western Junggar: Petrogenesis and Tectonic Implications

Late Carboniferous magmatism in the Western Junggar region of the Central Asian Orogenic Belt (CAOB) provides a critical geological record of regional tectonic and geodynamic history. In this study, we determined the zircon U-Pb isotopic compositions, bulk-rock Sr-Nd-Hf isotopic compositions, and major and trace element geochemistry of two granitic bodies in the Western Junggar, with the aim of constraining their emplacement ages, magmatic origin, and geodynamic significance. Radiometric ages indicate that the plutons were emplaced during the Late Carboniferous (322–307 Ma). Plutons in the North Karamay region are characterized by high Sr content (347–362 ppm) and low Y content (15.3–16.7 ppm), yielding relatively high Sr/Y ratios (20.8–23.7). They show consistent Yb (1.68–1.85 ppm), Cr (16–19 ppm), Co (7.5–8.1 ppm) and Ni (5.9–6.6 ppm) content, similar to that of modern adakites. The Hongshan plutons are characterized by high SiO2 (69.95–74.66 wt%), Na2O (3.26–3.64 wt%), and K2O (4.84–5.16 wt%) content, low Al2O3 (12.02–12.84 wt%;) and MgO (0.13–0 18 wt%) content, and low Mg# values (0.16–0.22). This group shows a clear geochemical affinity with A-type granites. All of the studied granitoids have positive εNd(t) (+4.89 to +7.21) and εHf(t) (+7.70 to +13.00) values, with young TDM(Nd) 806–526 Ma) and TDM(Hf) (656–383 Ma) ages, indicating a substantial addition of juvenile material. The adakitic granodiorites in the North Karamay region were likely generated via partial melting of thickened lower crust, while the A-type granites in the Hongshan area may have been derived from the melting of lower-middle crust in an intra-oceanic arc, which consists mainly of oceanic crust. The emplacement of these granitoids represents a regional magmatic “flare up”, which can be explained by the rollback of a subducting slab.