Intermediate-acid Rocks Research Articles

Geochemical prospectivity mapping using compositional balance analysis and multifractal modeling: A case study in the Jinshuikou area, Qinghai, China

To effectively map the prospecting targets related to deposit-type sought, local indicators of spatial association (LISA), compositional balance analysis (CoBA), and multifractal modeling were applied to process stream sediment geochemical data that are collected from the Jinshuikou area, Qinghai province, China. In this study, 14 elements, including Zn, Cu, Ni, Mo, Co, V, Ti, Sb, Ag, Pb, Sn, Hg, Cd, and W, were analyzed in 493 samples. The result of LISA shows that the ore-forming elements Zn and Cu have a close spatial autocorrelation, which supports the construction of balance b1 related to the Zn-Cu mineralization assemblage. A traditional contrast additive method was applied to compare with balance b1 for geochemical anomaly identification. The results clearly indicate that balance b1 significantly assisted with not only reduction of geochemical data internal imbalance caused by extreme value, but also intensification of Zn-Cu assemblage geochemical anomalies associated with Zn polymetallic mineralization. The high anomalies of the two balances, b5 (Co-V-Ti) and b8 (Sn-Pb-Ag-Sb), reflect well the distribution of basic and intermediate-acid rocks in the area, respectively. The geochemical distribution pattern of the balance b1 can be depicted by multifractal parameters such as singular index α, as well as asymmetry index R, which are useful for describing the spatial heterogeneity of the balance b1. The singularity indices of balance b1 were classified by the concentration-area (C-A) fractal model to produce the high potential areas of the Zn-Cu assemblage. The high potential areas were obviously correlated with all Zn polymetallic occurrences. So, combined with the metallogenic geological characteristics of the study area, five prospective prediction targets were mapped. The anomaly verification demonstrates that the Zn concentration has reached the lowest industrial grade and cut-off grade corresponding to the target area I-1 and I-2, respectively, and Cu also has certain metallogenic potential. There is good potential for Zn-Cu mineralization as represented by this integrated method.

Early Cretaceous sedimentary records of the early-stage continental rifting in the Songliao Basin, NE China

Well SK-2, a continental scientific drilling well in the Xujiaweizi fault depression of the Songliao Basin, has drilled through ca 2359 m of the Early Cretaceous Shahezi Formation. Herein, we focus on the sequence groups SSI and SSII in the lower part of the Shahezi Formation (interval 4357.38–5695.02 m) from well SK-2. There are fourteen different lithofacies and seven lithofacies associations. Syn-eruptive pyroclastic deposits and their proportions in successions indicate that SSI varies from dominantly pyroclastic fill to dominantly weathering-derived clastic fill, reflecting the development of volcanism in the early syn-rift stage. SSII exhibits another, similar evolutionary cycle. Whole-rock geochemistry of rocks from the Shahezi Formation reveals that the source rocks are felsic, andesite, and sedimentary rocks from the upper crust, and that the intermediate-acid rocks are originated from partial melting crustal materials and are hybridized with input from the mantle. In the seismic profile that intersects well SK-2, the thinning direction switches back and forth during the formation of the Shahezi Formation’s four sequence groups; that is, there is turnover superimposition in vertical stratigraphic subsidence, demonstrating strike-slipping during deposition of the Shahezi Formation.The major rift stage, especially during the deposition of the lower part of the Shahezi Formation, involved strike-slipping dominated extension. This conclusion is supported by the presence of abundant dark mudstone and coarse clastic progradation in the transgressive stage, as well as by the periodicity of volcanism combined with stratigraphic turnover superimposition.

Response of Paleogene Fine-Grained Clastic Rock Deposits in the South Qiangtang Basin to Environments and Thermal Events on the Qinghai-Tibet Plateau.

The Chamdo Basin is a secondary basin in the eastern part of Tibet China and is one of the most promising of petroliferous basins for new petroleum exploration. The Qamdo Basin records a complex burial history from the Mesozoic to the Cenozoic; however, the poorly constrained sedimentology of Cenozoic strata in this basin has severely obscured the overall profile and impeded further explorations of oil and gas resources. Here, we conduct whole-rock geochemical analyses of major, trace, and rare earth elements in fine-grained clastic rocks of the Paleocene Gongjue Formation, Qamdo Basin to reveal depositional environments, provenance, and tectonic setting. Petrologically, the Gongjue Formation is dominated by red fine-grained sandy mudstones/siltstones with ripple marks. The high values of the chemical index of alteration (avg. of 78.93), chemical index of weathering (avg. of 90.10), and index of compositional variability (avg. of 2.5) suggest that the basin has undergone heavy weathering. Cross-plots of La vs Th, Th vs Sc vs Zr/10, and Th vs Co vs Zr/10 reveal a continental arc tectonic setting. Paleosalinity (Sr/Ba), paleoclimate (Sr/Cu), and redox proxies (V/Cr, U/Th, and enrichment factors of Mo and U) indicate brackish to saline and oxidizing paleowater masses during deposition of the Gongjue Formation. Provenance analyses via elements and petrology reveal that sediments in the Gongjue Formation are mainly derived from intermediate-acidic rocks of the upper crust. We conclude that the first and third members are more arid climate and heavily chemically weathered than the second member. In combination with previous studies of the structural evolution of the Qamdo Basin since the Paleogene, a model is built to describe the sedimentary environment and evolution of the Qamdo Basin during transition to the Paleocene. The first and third members, i.e., the Eg1 and Eg3 members of the Gongjue Formation, are dominated by an oxidizing environment of seawater-saltwater, and the climate ranges from warm and humid to arid and hot, with relatively stable environmental changes. The Eg2 member of the Gongjue Formation is dominated by an oxidizing environment of seawater-saltwater, and the climate ranges from warm and humid to arid and hot, with more frequent environmental evolution. Our model aids in better understanding of the Paleocene climate evolution of the eastern Tibetan Plateau.

Late Cretaceous post-orogenic delamination in the western Gangdese arc: Evidence from geochronology, petrology, geochemistry, and Sr–Nd–Hf isotopes of intermediate–acidic igneous rocks

Late Mesozoic uplift of the Gangdese arc occurred prior to the India–Asia collision and was important in the evolution of the Tibetan plateau, but the geodynamic mechanisms that drove this process are unclear. In this paper, we report geochronological, petrological, geochemical, and Sr–Nd–Hf isotopic data for intermediate–acidic igneous rocks from the western Gangdese arc. These igneous rocks were emplaced at 87–67 Ma and are characterized by enrichments in light rare earth and large-ion lithophile elements, depletions in high-field-strength elements, high ( 87 Sr/ 86 Sr) i ratios (0.7074–0.7116), and low ε Nd (t) (−7.5 to −4.1) and ε Hf (t) values (−16 to 0.8). These magmas were most likely derived by high-temperature (960–1200 °C) partial melting of the thickened crustal materials, with minor mantle input, related to post-orogenic lithospheric delamination. The increasing ε Nd (t) and ε Hf (t) values and decreasing initial Sr isotope ratios from the ca. 87 Ma diorites to ca. 67 Ma diorites and rhyolites indicate an increasing mantle contribution as delamination proceeded. Estimated pressure conditions for the high-Sr/Y gabbroic diorites indicates the magmas were derived from crust at pressures of up to 19 kbar (i.e., a depth of ~66 km). Therefore, the western Gangdese arc had been thickened during the Late Cretaceous, possibly due to the flat-slab subduction of Neo-Tethyan oceanic lithosphere and coeval collision of the Qiangtang–Lhasa terranes. • Intermediate–acidic rocks in the western Gangdese arc emplaced from 87 to 67 Ma. • Geochemical indices show they formed dominantly by melting of crustal material. • They formed at 960–1200 °C by melting of thickened crust with minor mantle input. • Nd-Hf-Sr isotopes indicate more mantle involvement following ongoing delamination. • Western Gangdese arc has been thickened during the Late Cretaceous.

Significance of sandstone provenance in tracking potential uranium reservoirs: A case study of the Middle Jurassic Zhiluo Formation, western Ordos Basin, northern China

The Middle Jurassic Zhiluo Formation is the main uranium-bearing sequence in the western Ordos Basin, northern China. Provenance studies of clastic rocks in the Zhiluo Formation are important to provide guidelines for uranium exploration. In this paper, we describe the sandstones from the Zhiluo Formation and report their bulk rock elemental compositions by using samples that were collected from the Lingwu area, western Ordos Basin. Our main objective is to provide constraints on the provenance of the sandstones and thus new insights into uranium exploration. The results show that the sources of the Zhiluo Formation sandstones have TTG (trondhjemite-tonalite-granodiorite) attributes and mainly consist of magmatic arc orogenic belts that were mixed with continental blocks and recycled orogenic belt materials. The paleocurrent measurements that average 144° suggest that the provenance supply direction of the sandstones is from northwest to southeast. Combined with the regional tectonic settings, it can be inferred that the sandstone provenance was mainly provided by the Xingmeng Orogenic Belt, while the Alxa Block and Helan Mountain complex rocks also contributed. Our research might provide a crucial reference for predicting the locations of potential uranium reservoirs, i.e., the search for uranium mineralization should target the northwest of the Ordos Basin, especially near regions where intermediate-acid rocks are present. This information is integrated into a predictive model in which tracking along the provenance supply directions of clastic sediments is an efficient method for conducting uranium exploration in a sedimentary basin.

Recognition of Significant Multi-Element Geochemical Signatures of Lower Soil on Hainan Island, China: Implications for Thermal Mineral Water Exploration

As an important geothermal resource, thermal mineral water has high resource efficiency and thermal energy efficiency. The aim of this study was to delineate prospective areas of thermal mineral water based on potential thermal mineral water sites and faults. Linear regression was used to process the temperature of 22 known thermal mineral water sites as dependent variables, and 54 indices of the lower soil of multipurpose regional geochemical surveys as independent variables, in the area of intermediate-acid intrusive rocks and sediment degeneration rocks on Hainan Island. Published data were quoted from the National Multi-Purpose Regional Geochemical Survey (Hainan Province, China). According to the regressive modelling of 2197 lower soil samples, 547 potential thermal mineral water sites were delineated after considering 4 factors—geological background, regional structure, interval of dependent variable’s predictive temperature, and boundary of independent variable’s contents—which were compared against 22 known thermal mineral water sites to choose the 2197 lower soil samples, based on the choice of prospective sites of thermal mineral water on Hainan Island. The results showed that the proportion of A1-level sites that were >70 °C constituted 11% of all A1-level prospective sites, reflecting the superiority of east–west or north–east directional regional faults in controlling the distribution of thermal mineral water. This study shows the indications of the multipurpose regional geochemical survey with regards to thermal mineral water, which is one of the most important tourist resources of Hainan Island.

Volcanism from different eruption cycles during the Early Cretaceous in the Changling fault depression of the songliao basin, NE China, and their implications for timing of lithospheric thinning

ABSTRACT Late Mesozoic lithospheric extension in NE China resulted in the development of a large extensional province and widespread formation of volcanic-sedimentary basins. The Songliao Basin is the largest one and contains voluminous volcanic rocks composing the majority of the basin fill. This study focuses on two adjacent eruption cycles, the Huoshiling Formation (K1h) and the first member of the Yingcheng Formation (K1yc1), in the Changling fault depression of the Songliao basin, constrains their time ranges and compares the origins of volcanic rocks. Zircon populations from K1h yield U-Pb ages of 124–118 Ma; those from K1yc1 yield younger ones (115–106 Ma). Different volcanic rocks are identified in K1h (alkaline basic rocks, calc-alkaline intermediate-acid rocks) and K1yc1 (alkaline basic rocks, A-type rhyolites), and their geochemistry and isotope characteristics confirm their different origins. The alkaline basic rocks from K1h have the similar magma source as those from K1yc1; both formed under within-plate conditions from an ocean island basalt (OIB)-type mantle source, assumed to be the heterogeneous shallow asthenosphere. The calc-alkaline intermediate-acid volcanic rocks from K1h formed by fractional crystallization of magma, related to the enriched lithospheric mantle, whereas the A-type rhyolites from K1yc1 directly originated from the partial melting of crust newly formed from the depleted mantle. The development of alkaline basic rocks and A-type acid rocks, a typical bimodal volcanic assemblage in K1yc1, requires a relatively thin lithosphere and thus implies that lithospheric thinning reached its maximum during this time (115–106 Ma). However, the rare expression of alkaline basic rocks and the formation of acid rocks mainly by fractional crystallization in K1h indicate that the lithosphere was relatively thick; during this time (124–118 Ma), the lithosphere below the Songliao Basin had just begun thinning. These different stages of lithospheric extension may be due to the intermittent rollback of the Palaeo-Pacific Plate.

Characteristics of the Cretaceous Magmatism in Huanghua Depression and Their Relationships with Hydrocarbon Enrichment

The Huanghua depression located in the hinterland of the Bohai Bay Basin in eastern China is a typical area for the research of multistage magmatic activities with hydrocarbon enrichment, many high-yield wells related to igneous rocks were discovered within the Cretaceous strata in recent years. However, the spatial and temporal distribution of Cretaceous igneous rocks remains unclear, and the relationships among magmatic sequence, lithology, and hydrocarbon enrichment have been poorly studied. In order to solve these problems, core observation, logging analysis, major element analysis, zircon U-Pb chronology, oil-bearing grade statistics and reservoir spaces analysis were used to subdivide the magmatism cycles and to investigate the characteristics of igneous reservoirs. Our results show that the Mesozoic magmatism in Huanghua depression started in 140.1±1.4 Ma and could be divided into two stages including the Early Cretaceous stage and Late Cretaceous stage. The Early Cretaceous magmatism principally developed basic-intermediate rocks in the north zone, and could be subdivided into 3 cycles with their forming ages of 140, 125–119, and 118–111 Ma, respectively. By contrast, the late stage mainly developed intermediate-acid rocks centralized in the south zone and formed at 75–70 Ma. The GR and SP curves are good indicators for the contrast of different lithologies, lithofacies and for magmatic sequences division. Intensive magmatism may have an advantage to form reservoirs, since basalt in cycle III in the Early Cretaceous and dacite porphyrite in the Late Cretaceous have great exploration potential. Lithology and tectonic fractures have an important influence on the formation of reservoir spaces and hydrocarbon enrichment. The characteristics of Cretaceous magmatism and igneous reservoirs in Huanghua depression and adjacent areas are summarized, providing important information for igneous reservoirs research and oil-gas exploration in the Cretaceous in related areas.

Adakitic rocks at convergent plate boundaries: Compositions and petrogenesis

Adakitic rocks are intermediate-acid magmatic rocks characterized by enrichment in light rare-earth elements, depletion in heavy rare-earth elements, positive to negligible Eu and Sr anomalies, and high La/Yb and Sr/Y ratios. Cenozoic adakitic rocks generated by partial melting of subducted oceanic crust (slab) under eclogite-facies conditions (i.e., the original definition of “adakite”) occur mainly in Pacific Rim volcanic arcs (intra-oceanic, continental, and continental-margin island arcs), whereas those generated by partial melting of thickened lower crust occur mainly in Tethyan Tibetan collisional orogens. In volcanic arcs, adakitic melts derived from the melting of subducted oceanic crust metasomatize the mantle wedge to form a unique rock suite comprising adakite-adakite-type high-Mg andesite-Piip-type high-Mg andesite-Nb-rich basalt-boninite. This suite differs from the basalt-andesite-dacite-rhyolite suite formed from mantle wedge metasomatized by fluids derived from subducted oceanic crust. Previously published data indicate that partial melting of mafic rocks can generate adakitic magmas under pressure, temperature, and hydrous conditions of 1.2–3.0 GPa, 800–1000°C, and 1.5–6.0 wt.% H2O, respectively, leaving residual minerals of garnet and rutile with little or no plagioclase. Cenozoic Au and Cu deposits occur proximally to adakitic rocks, with host rocks of some deposits actually being adakitic rocks. Adakitic rocks thus have important implications for both deep-Earth dynamics and Cu-Au mineralization/exploration. Although studies of Cenozoic adakitic rocks have made many important advances, there remain weaknesses in some important areas such as their tectonic settings, petrogenesis, magma sources, melt-mantle interactions of pre-Cenozoic adakitic rocks, and their relationship with the onset of plate tectonics and crustal growth. Future research directions are likely to involve (1) the generation of adakitic magmas by experimental simulations of partial melting of different types of rock (including intermediate-acid rocks) and magma fractional crystallization at different temperatures and pressures, (2) the relationship between magma reservoir evolution and the formation of adakitic rocks, (3) the tectonic setting and petrogenesis of pre-Cenozoic adakitic rocks and related geodynamic processes, (4) interactions between slab melts and the mantle wedge, (5) the formation of Archean adakitic tonalite-trondhjemite-granodiorite and its link to the onset of plate tectonics and crustal growth, and (6) the relationship between the formation of adakitic rocks and metal mineralization in different tectonic settings.

Petrography and geochemistry of Neoproterozoic charnockite–granite association and metasedimentary rocks around Okpella, southwestern Nigeria

The Neoproterozoic charnockite–granite association of Okpella intrudes metasedimentary and migmatite-gneiss complex rocks in the eastern Igarra Schist Belt, southwestern Nigeria. In order to unravel the complex processes involved in the formation and tectonic evolution of the Igarra Schist Belt during the Neoproterozoic, detailed field, petrographic and whole-rock geochemical study of the charnockite–granite association and metasedimentary rocks around Okpella was conducted. Published data on the metasedimentary rocks and Pan-African granitoids in different sectors of the belt were also compiled for detailed interpretations. The charnockites and granites of Okpella show primary magmatic mineralogy and geochemical characteristics. They are silicic (> 63 wt% SiO2), metaluminous to peraluminous, high-K calc-alkaline, ferroan, post-collisional granitoids. The garnet-biotite schist, calc-silicate gneiss and quartzite in the area are low–medium grade metasedimentary rocks. The mineralogy and geochemistry of the charnockites suggest that the charnockitic melt was derived from mafic lower continental crust through partial melting and assimilation-fractionation processes. The granites probably originated from mixed melts derived from lower- to mid-crustal tonalites-trondhjemites-granodiorites and/or subducted metagreywackes and mantle-derived magmas (probably the charnockitic melt and/or its progenitor). The granites and charnockites are coeval and were presumably emplaced during the post-collisional stages of the Pan-African Orogeny. The garnet-biotite schist, calc-silicate gneiss and quartzite represent metamorphosed immature to slightly mature sedimentary rocks, probably greywacke, marl and subarkose, respectively, that were sourced from intermediate–acid rocks which underwent low–moderate chemical weathering with minor contribution from recycled sediment sources and deposited in active continental environments. The Neoproterozoic evolution of the Igarra Schist Belt, therefore, involved deposition and infolding of sediments in active continental margin during the early Pan-African followed by upwelling of basaltic magma from the mantle which underplated and crystallized in the lower continental crust and was subsequently partially melted to generate the charnockitic and granitic melts through mantle-crust interaction during the late Pan-African.

Late Early-Cretaceous Magma Mixing in the Langqi Island, Fujian Province, China: Evidences from Petrology, Geochemistry and Zircon Geochronology

The mafic enclaves from Mesozoic intermediate-acid magmatic rocks, widely developed along Fujian coast, are considered to be the results of large-scale crust-mantle interaction and magma mixing. In this paper, petrography, mineralogy, and geochemistry of granites and mafic microgranular enclaves (MMEs) in Langqi Island are studied to provide new information for tracing crust-mantle interaction. The zircon U-Pb dating results show that the Langqi rocks were formed at ~101 Ma, which are metaluminous, enriched in silica and high-K calc-alkaline I-type granites. The enclaves have a typical magmatic structure, which is characterized by magma mixing between high-temperature basic magma and low-temperature acidic magma through injecting. The enclaves and host granites show a tendency to mixed major and trace elements, displaying a clear-cut contact relationship, which is indicative of coeval magmatism. The genesis of Langqi rocks is related to the extensional setting caused by the subduction of Paleo-Pacific Plate, and they are the results of mixing of subduction-related metasomatized mantle-derived mafic and induced crustal-melted granitic magma originating from partial melting of the crustal material.

Early–Middle Permian southward subduction of the eastern Paleo-Asian Ocean: Constraints from geochronology and geochemistry of intermediate-acidic volcanic rocks in the northern margin of the North China Craton

The northern margin of the North China Craton (NCC) resulted from complicated subduction-accretion process of the eastern Paleo-Asian Ocean (PAO), thus late Paleozoic magmatic records in this region could place conclusive constraints on the final-stage subduction processes of the eastern PAO. Here we present petrological, geochronological, geochemical, and in situ zircon Hf isotopic data of the late Paleozoic intermediate-acidic volcanic rocks, and compiled age and geochemical data of the Permian magmatic rocks along the northern margin of the NCC, with the aim of elucidating their ages, petrogenesis and tectonic implications. Zircon UPb ages indicate that these rocks formed in the early–middle Permian (275–267 Ma). Lithologically, these volcanic rocks are composed mainly of andesites, with minor rhyolites and dacites. The studied andesites contain 53.94–64.87 wt% SiO2, 1.86–3.05 wt% MgO and 0.47–3.56 wt% K2O, and belong to low-K calc-alkaline to shoshonite series. Coupled with variable zircon εHf(t) values of −14.57 to +12.57, we propose that the parental magma was derived from partial melting of heterogeneous lithospheric mantle resulted from metasomatism of subduction-related fluids. In contrast, the rhyolite-dacite suites are distinguished by higher SiO2 (65.94–74.77 wt%) and lower MgO (0.15–1.60 wt%) contents, indicating an affinity with highly fractionated I-type granite originated by partial melting of lower crust. These intermediate-acidic rocks are characterized by enrichment in large-ion lithophile elements (LILEs; e.g., Rb, Th, and K) and depletion in high-field-strength elements (HFSEs; e.g., Nb, Ta, P, and Ti), suggesting that they formed in an active continental margin setting. These geochemical features and lithological assemblage, together with the East-West-trending Permian magmatic belt with arc affinities, indicate that their generation was related to southward subduction of the Paleo-Asian oceanic lithosphere beneath the NCC. Synthesized data from this and previous studies lead us to favor a double-sided, early–middle Permian subduction model, with the PAO not closed prior to the middle Permian.

Using Factor Analysis to Determine the Interrelationships between the Engineering Properties of Aggregates from Igneous Rocks in Greece

This paper investigates the interrelationships between the engineering properties of igneous aggregate rocks from Greece with the aid of the R-mode factor analysis. The collected samples represent mafic and ultramafic rocks from the ophiolite complexes of Gerania, Guevgueli, Veria-Naousa, and Edessa as well as intermediate-acidic rocks from the surrounding areas of the complexes. Factor analysis verifies the important interdependences among the engineering parameters like physical, mechanical, geometrical, and physicochemical properties by giving statistical significance. Variations of the petrographic characteristics of the investigated rocks influence their engineering properties as well as the interdependence among them. Factor 1, which is the most representative one (~36% of the total variance), shows interdependences between certain physical, mechanical, physicochemical properties such as total porosity (nt) with moisture content (w), nt with the Los Abrasion value (LA), and the uniaxial compressive strength (UCS) with point load index Is(50). Additionally, the second factor (~27% of the total data variability) correlates physical properties such as w, nt, physicochemical properties such as the methylene blue test (MBF), mechanical properties such as UCS, Is(50), and loss on ignition (LOI), which highlights the effect of mineralogy on these properties. Lastly, Factor 3 (~14% of the total data variability) expresses the interdependence of the flakiness index (IF), which is an elongation index (IE) relative to their alteration (LOI).

Progress and challenges of big data research on petrology and geochemistry

We are entering the era of big data, and big data achievements have benefited ordinary people. However, big data application in geochemistry research has not been really appreciated. Big data is a kind of method and a pattern of thought. It is different from traditional scientific research methods and thinking in that it starts from the data and adopts full data mode. This paper introduces basalt, andesite and continental marginal arc basalt tectonic environment discrimination diagrams made by the author and his collaborators using all the global rock geochemical data available. We have discussed the following scientific problems of petrology and geochemistry using big data research: 1. we found many better illustrations in the study of discriminant diagrams, mainly relying on the relationship among the major elements, transition elements, and metal elements. What the points between the relationships are? Why did they work? These new questions need to be studied by the geochemists. 2. Data mining found that mid-ocean ridge is extremely lack of intermediate-acidic rocks. Does it mean that the upper mantle is an acute shortage of water? 3. This study found that the Miocene is the most developed epoch of magmatic activities. The Miocene appeared many important geological events in the world. Is there a connection between them? 4. The Miocene adakite most developed in the world, according to adakite exposed. There may be a giant Eurasian plateau from the Tibetan plateau to the Carpathians. 5. According to the spatial and temporal distribution of Cenozoic picrite, we put forward how to realize a global hotspot issues, etc. The paper also put forward some suggestions of further research and emphasized that science has entered the era of big data. In the era of big data, scientific classification standards have changed: any discipline which can be expressed in data is called science, and which cannot be expressed in data is called non-science. Whether it can be expressed by data is the watershed of science and non-science. In the era of big data, the geology encountered an unprecedented crisis. According to our forecast, in the foreseeable future, geophysics will be far ahead of geology. Space science will boom, and geochemistry will lead the way for a long time in the field of geology.

Heavy Mineral Characteristics and Their Implication for Provenance of the Middle to Upper Triassic on the Northwest Margin of Junggar Basin, North China

Heavy minerals are extremely sensitive indicators of provenance. Applying the methods of heavy mineral combination analysis, content distribution analysis, SPSS statistical component analysis, and correlation analysis, 18 heavy minerals are identified in the northwestern margin of the Junggar Basin (NW Junggar). According to the analysis of the heavy mineral characteristics and coefficients, 4 heavy mineral combinations are developed in the study area: Zircon-tourmaline-monazite-apatite-anatase, rutile-ilmenite-leucoxene-apatite-galenite, hematite-limonite-pyrite, and magnetite-epidote-hornblende. Previous results predicted that source rocks consist of intermediate-acidic magmatite, sedimentary rocks and metamorphic rocks, and intermediate-acidic magmatite is considered to be the main source rock. Furthermore, combined with the geological background of NW Junggar, Qier-Halaalat Mountain, which belongs to the Zaire Mountain front, is shown to be the provenance of the study area. The main sources of sediments are flesh-red granite, grey and greyish-green andesite, andesitic-porphyrite, grey and grayish-black tuff, siltstone, and sandstone of the Lower Carboniferous Tailegula Formation. Additionally, because of the high content of the angular-subangular and subangular-subrounded heavy mineral grains, these heavy minerals are both from near and distal provenance, with most being near-provenance deposits. During the process of provenance propulsion on the margin of the basin, clastics are mixed together and affected by regional dynamic metamorphism, which is probably the main reason for the existence of the metamorphic component.

Geochemical analysis and origin of gas in volcanic reservoirs in the Songliao Basin

Volcanic reservoirs are extensive in the Songliao Basin and mainly include intermediate-basic rocks in the northern part, intermediate-acidic rocks in Xujiaweizi in the southern part, and acidic rocks in the Jinglin block. The natural gas in the volcanic reservoirs of the Songliao Basin has a wide range of compositions, with alkanes being dominant in most cases, although carbon dioxide is dominant in some wells. Generally, the gas in the volcanic rocks near deep faults has high contents of carbon dioxide, whereas the natural gas in volcanic rocks far from faults has low carbon dioxide contents. The gas in the volcanic reservoirs is of multiple origins, including abiogenic gas of probable mantle origin (generally found in wells with high carbon dioxide contents) and organic gas mainly derived from organic matter in the basin. The abiogenic alkanes have δ13C values in the order of δ13C1 > δ13C2 > δ13C3 > δ13C4, which is opposite that of alkanes of organic origin. The 3He/4He ratios of the fluid inclusions from the volcanic reservoirs range from 0.286 × 10−6 to 7.33 × 10−6, with an average of 2.48 × 10−6, and the R/Ra ratios range from 0.26 to 5.24, with most values being greater than 1.0, indicating mixed origins of noble gases from the crust and the mantle. The gas in fluid inclusions from the volcanic reservoirs has δ13C1 values ranging from −17.1 to −28.7‰ (PDB), δ13C2 values ranging from −23.4 to −32.4‰ (mostly approximately −25‰), and δ13Cco2 values ranging from −10.97 to −21.73‰, which are significantly different from the isotopic compositions of the gas in the present reservoirs, suggesting that some abiogenic alkanes may have been charged into the reservoirs during the geologic history of the basin. The early charged CO2 is mainly organic in origin, while the abiogenic CO2 was charged during the main accumulation period, producing a mix of origins for the gas in the volcanic reservoirs of the Songliao Basin. The abiogenic alkanes, He, and CO2 in the natural gas indicate the addition of some abiogenic gas to the gas. According to the relationship between the distribution and attitude of volcanic rocks and faults, we found that the abiogenic gas reservoirs are located near fault zones, whereas the organic and mixed gas reservoirs are located far from fault zones. The geochemical study of natural gas is helpful in determining the origin and spatial distribution patterns of gas in deep volcanic reservoirs and for directing further gas exploration in the Songliao Basin.

Provenance and geochemical behavior of fluorine in the soils of an endemic fluorosis belt, central Iran

The concentration of fluorine, major, trace and rare earth elements (REEs) were used to estimate the probable sources and provenance of fluorine in the soils of an endemic fluorosis belt in central Iran. Total fluorine (TF) in soils varied from 146 to 406 mg/kg with a mean of 277.5 mg/kg. Calculated enrichment factor (EF) and single factor pollution index (SFPI) revealed that the majority of soil samples were moderately contaminated by fluorine. The very strong positive correlation of TF with weathering indices and soil's fine sized fractions indicated that chemical weathering and alteration of parent rocks/soils are the main controlling factors of fluorine behavior in soils. Fluorine affinity to immobile transition trace elements and REEs suggested the role of heavy minerals as the potential F host phases. Modal mineralogy along with SEM-EDX analysis indicated that apatite, fluorapophyllite, epidote, biotite, muscovite and chlorite, as well as, clay minerals are the main F-bearing minerals in the studied soils. Discriminant, bivariate and ternary diagrams of elemental compositions displayed similar geochemical signature of soils to intermediate-acidic rocks and local shales. Based on the weathering indices, soils were immature and showed a non-steady state weathering trend from upper continental crust (UCC), acidic and intermediate igneous source rocks towards shale composition possibly due to mixing of moderately weathered and un-weathered sources of different primary compositions.

Geochemical and Sr-Nd-Pb-Li isotopic characteristics of volcanic rocks from the Okinawa Trough: Implications for the influence of subduction components and the contamination of crustal materials

Abstract The Okinawa Trough is an infant back-arc basin developed along the Ryukyu arc. This paper provides new major and trace element and Sr-Nd-Pb-Li isotope data of volcanic rocks in the Okinawa Trough and combines the published geochemical data to discuss the composition of magma source, the influence of subduction component, and the contamination of crustal materials, and calculate the contribution between subduction sediment and altered oceanic crust in the subduction component. The results showed that there are 97% DM and 3% EMI component in the mantle source in middle trough (MS), which have been influenced by subduction sediment. The Li-Nd isotopes indicate that the contribution of subduction sediment and altered oceanic crust in subduction component are 4 and 96%, respectively. The intermediate-acidic rocks suffer from contamination of continental crust material in shallow magma chamber during fractional crystallization. The acidic rocks in south trough have experienced more contamination of crustal material than those from the middle and north trough segments.

Geochronology, geochemistry, and Hf isotopes of Jurassic intermediate-acidic intrusions in the Xing’an Block, northeastern China: Petrogenesis and implications for subduction of the Paleo-Pacific oceanic plate

Zircon U–Pb dating, whole-rock geochemistry, Hf isotopic compositions, and regional geological observations of Jurassic intermediate-acidic intrusions in the Xing’an Block, northeastern China, are presented to constrain their petrogenesis and the tectonic evolution of the Paleo-Pacific Ocean. Zircon U–Pb age dating indicates that the intrusions were emplaced in three stages: during the Early Jurassic (180–177Ma), Middle Jurassic (171–170Ma), and Late Jurassic (∼151Ma). Despite the wide range in ages of the intrusions, the magmas of Jurassic acidic intrusions were likely derived from a similar or common source and experienced different degrees of magmatic differentiation, as inferred from their geochemical and Hf isotopic characteristics. The Jurassic acidic intrusions are characterized by high SiO2 and total Na2O+K2O, low MgO, and I-type affinities, suggesting that the primary magmas were derived from partial melting of lower crustal material. These findings, combined with their εHf(t) values and two-stage model ages, indicate the primary magmas originated from partial melting of juvenile crustal material accreted during the Neoproterozoic to Phanerozoic. The Middle Jurassic intermediate-acidic rocks (diorites and granodiorites of the TJ pluton) have SiO2 contents of 57.96–69.10 wt.%, MgO contents of 4.48–1.81 wt.%, and high Mg numbers (45–54). They are enriched in large ion lithophile elements (e.g., Rb, Ba, Th, U, and K) and light rare earth elements, depleted in high field strength elements (e.g., Nb, Ta, Zr, Hf, and Ti) and heavy rare earth elements, and have εHf(t) values of +6.5 to +9.1. These data suggest that the magma was derived from partial melting of a depleted mantle wedge that had been metasomatized by subduction-related fluids. According to these findings and previous studies that focused on contemporaneous magmatic–tectonic activity in northeastern China, we conclude that the generation of Jurassic intermediate-acidic intrusions in the Xing’an Block was related to subduction of the Paleo-Pacific oceanic plate.

In situ zircon Hf–O isotopic analyses of late Mesozoic magmatic rocks in the Lower Yangtze River Belt, central eastern China: Implications for petrogenesis and geodynamic evolution

A combined study of whole-rock major and trace elements, Sr–Nd isotopes, zircon U–Pb dating, and in situ zircon Hf–O isotopes has been carried out for late Mesozoic magmatic rocks in the Lower Yangtze River Belt. The results provide insights into the origin of mantle sources of magma above a subduction zone, and thus into the petrogenesis of high-K calc-alkaline rocks, shoshonites, and A-type granites on continental margins, and the associated tectonic transformation from a continental arc to a back-arc extensional setting. The late Mesozoic magmatism can be subdivided into three stages: high-K calc-alkaline intrusions (148–133Ma), shoshonitic rocks (133–127Ma), and A-type granitoids (127–123Ma). All the rocks have consistent arc-like trace element characteristics with positive anomalies of Rb, Th, U, Pb, and LREE, negative anomalies of Nb, Ta, and Ti, and enriched Sr–Nd–Hf isotopic signatures. The first-stage intrusions in the Tongling area usually host dark enclaves of diorite, have high Sr/Y ratios, and low Y contents, and contain zircons with relatively low εHf(t) values (−38.6 to −6.6) and high δ18O values (5.7‰ to 10.1‰). A few inherited zircons with Neoarchean to Paleoproterozoic ages and highly enriched Hf isotopic compositions were detected in both the host intrusive rocks and the enclaves. The second-stage Ningwu volcanics contain zircons with moderate εHf(t) values (−13.3 to −3.8) and elevated δ18O values (5.4‰ to 7.6‰). The third-stage intrusions can be divided into A1- and A2-type granitoids, and their zircons have relatively high δ18O values of 6.7‰ to 10.3‰ and high εHf(t) values of 0 to −7.9. Based on these geochemical data we drew the following conclusions. Before 148Ma, following metasomatism by slab-derived fluid/melts, partial melting of the lithospheric mantle produced basaltic magma in the context of a subducting paleo-Pacific plate. This basaltic magma mixed with magma derived from the Archean lower crust, and the underplated and thickened juvenile lower crust. From 148 to 133Ma, continuous production of these mixed magma resulted in their intrusions as basic rocks at shallow levels. Meanwhile, partial melting of the thickened juvenile crust formed the intermediate-acid rocks of the first stage. As subduction continued, and the dip angle of the subducting plate increased, the continental arc tectonic setting was transformed to one of back-arc extensions. Metasomatism and decompression induced intensive partial melting of the lithospheric mantle, and these magmas, together with a limited amount of assimilated crustal materials, formed the second-stage volcanics. Roll-back of the subducted slab resulted in extension, causing disassembling of the lower lithosphere and lithospheric thinning, and the upwelling of hot asthenosphere. The A2-type granites were the result of the reworking of the Mesoproterozoic juvenile crust in this tectonic setting of extension. On the other hand, the A1-type granitoids were formed from magmas that were derived both from the matasomatized mantle and from the A2-type granitic material that had its origins in the Mesoproterozoic juvenile crust. We suggest that an integrated and comparative study of the multiple stages of development of these magmatic rocks is the key to understanding the tectonic evolution and associated magmatic activities in this continental intraplate setting.