The Zhegu region, located in southern Tibet, is positioned within the central and eastern segments of the Tethys Himalayan tectonic belt. In this area, mafic igneous rocks are predominantly intrusion into Jurassic strata, occurring as vein-like bodies. This study presents zircon U-Pb age determinations and whole-rock geochemical analyses of diabase and gabbro samples from the region, aimed at elucidating their petrogenesis and geodynamic background. The zircon U-Pb ages yield crystallization ages of 130.7 ± 1.5 Ma for diabase and 131.6 ± 2.5 Ma for gabbro, both of which are consistent with the crystallization ages of ocean island basalt (OIB)-type mafic rocks in the Comei Large Igneous Province (130–136 Ma). Geochemical data reveal that these mafic rocks are characterized by elevated TiO2, FeOT, and P2O5 contents, alongside relatively low MgO content, indicative of tholeiitic affinities. They exhibit enrichment in light rare earth elements (LREEs) and high field strength elements (HFSEs) such as Nb, Hf and Y, resembling OIB signatures. These rocks show evidence of fractional crystallization without significant crustal contamination. Melting models suggest that the magmas originated from partial melting of a garnet-lherzolite mantle source. The petrogenetic characteristics of these rocks reflect interactions between the Kerguelen mantle plume and the overlying lithospheric mantle.

The Nanyangtian scheelite deposit is located in the Nanwenhe-Song Chay dome (NSCD), southeastern Yunnan. This deposit has undergone four metallogenic stages and is characterized by several kilometers of bedded scheelite-bearing skarn (NYT-II stage), feldspar-bearing quartz veins (NYT-III stage), and sulfides (NYT-IV stage) in the Neoproterozoic schist and gneiss, all of which exhibit similar fold deformations. Throughout the stages, Th and salinity of fluids gradually decrease, weakly and positively correlating, representing a slow cooling process. NYT-I fluids (F-, H2O-rich and high T, p), as indicated by the plagioclase within feldspar-bearing quartz veins, may have directly evolved from a highly fractional residual melt or a salt-rich aqueous melt, signifying the magmatic-hydrothermal transition. From NYT-II to NYT-III fluids, a wider variation of delta O-18(H2O) (-2.4 similar to 5.1 parts per thousand) to a narrow range of delta O-18(H2O) (2.8 similar to 5.1 parts per thousand), and a narrow delta S-34 range (5.18 parts per thousand similar to 8.62 parts per thousand) also indicates that fluids may evolve from the relatively oxidized granitic magma. Furthermore, NYT-I fluids could extend throughout the entire fluid evolution, culminating in two diverse paths: one is a much purer magmatic water towards the NYT-III and NYT-IV fluids, and the other is a more meteoric water-dominated towards the NYT-II fluids. A lower water/rock ratio (W/R) existed in the NYT-II stage, leading to the formation of moderately oxidized Tungsten (W)-skarns and scheelites through the NYT-I salt-rich aqueous melts or their reactions with wall rocks in a stable environment. W/R ratios increased in the NYT-III stage, resulting in the formation of NYTIII feldspar-bearing quartz veins with CO2 generation and alkalinity enhancement. As oxidation diminished, fluids gradually evolved into the NYT-IV fluids, forming sulfides.

The Zhegu area in southern Tibet is situated in the central and eastern part of the Tethys Himalayan tectonic belt, with the Kangbuzhenri area being abundant in gneissic granites. This study examines the petrology, chronology, and geochemistry of the Kangbuzhenri gneissic granite, providing insights into its Pan-African and Early Paleozoic geological evolution. The zircon U-Pb chronology indicates an upper intercept age of ~539 Ma, reflecting Pan-African orogenic events in the eastern part of the Tethys Himalayan tectonic belt, and a lower intercept age of ~144 Ma, representing a late tectonic–thermal event. Geochemically, the gneissic granites are calc-alkaline peraluminous rocks with high SiO2 and Al2O3 contents and low TiO2, P2O5, MgO, and FeOT contents. The gneissic granites are enriched in LREE and LILEs (Rb, Pb, Th, U, etc.), but relatively depleted in HREE and HFSEs (Nb, Ti, P, etc.). Most of them show a weak negative δEu anomaly, except for two samples which show a significant negative δEu anomaly due to the crystallization of plagioclase. Based on the above study, most of the gneissic granites exhibited the characteristics of an I-type granite, while two of the samples were a highly differentiated I-type granite with S-type affinities. All the above characteristics indicate that the gneissic granite likely originated from the partial melting of crustal materials and sediments with a minor involvement of mantle-derived materials. Combined with the previous chronological studies, the Kangbuzhenri gneissic granites were formed in an extensional tectonic environment during post-collision orogeny and then they were influenced by the Kerguelen mantle plume tectonic–thermal event around ~144 Ma and the subsequent Southern Tibet Detachment System (STDS).

The Hawaiian-Emperor seamount chain has shown two subparallel geographical and geochemical volcanic trends, Loa and Kea, since ∼5 Ma, for which numerous models have been proposed that usually involve a single mantle plume sampling different compositional sources of the deep or shallow mantle. However, both the dramatically increased eruption rate of the Hawaiian hotspot since ∼5 Ma and the nearly simultaneous southward bending of the Hawaiian chain remain unexplained. Here, we propose a plume-plume interaction model where the compositionally depleted Kea trend represents the original Hawaiian plume tail and the relatively enriched Loa trend represents an emerging plume head southeast of the Hawaiian plume tail. Geodynamic modeling further suggests that the interaction between the existing Hawaiian plume tail and the emerging Loa plume head is responsible for the southward bending of the Hawaiian chain. We show that the arrival of the new plume head also dramatically increases the eruption rate along the hotspot track. We suggest that this double-plume scenario may also represent an important mechanism for the formation of other hotspot tracks in the Pacific plate, likely reflecting a dynamic reorganization of the lowermost mantle.

There are potential genetic relationships between I- and A-type granitoids, which remain obscure. The origin of transitional I-A-type intrusions could provide new clues for this issue and are important in deciphering the origin of A-type intrusions. Here we report geochemical and isotopic compositions of transitional I-A-type syenites (Makou pluton) from the Luzong Basin in the Lower Yangtze River Belt (LYRB). The Makou pluton is composed of gabbros and syenites. Zircon U-Pb ages reveal that it was formed at similar to 130 Ma, which was slightly earlier than typical A-type intrusions in the LYRB. Geochemical features indicate that the Makou syenites belong to transitional I-A-type igneous rocks. The Sr-Nd-O isotopic compositions and the correlation between major and trace elements of Makou gabbros and syenites suggest that they are cogenetic, whereas the syenites experienced further magma evolution. Geochemical characteristics, especially the high Nb content of gabbros, suggest that the mantle source of the Makou pluton was metasomatized by melts from subducted sediments and slabs, which is similar to Huangmeijian A-type intrusion in the Luzong Basin. Makou syenites have different evolution conditions, e.g., the temperature and oxygen fugacity, compared with the Huangmeijian A-type intrusion. The ferroan character of the Makou syenites was weakened by crystal fractionation at relatively high oxygen conditions to produce the transitional I-A-type intrusions, due to more addition of fluids derived from subducted slabs to the source. This is consistent with the partial melting of the metasomatized lithosphere mantle due to asthenosphere upwelling as a result of ridge subduction beneath the LYRB.

Ridge subduction usually has significant influences on the tectonics, magmatic activity and mineralization of the overriding plate because of its special thermal and topographic structures. The Neo-Tethys is a vanished ancient ocean, and thus, its spreading ridge must have been subducted beneath the Eurasian continent. However, where and when the subduction of the Neo-Tethys ridge occurred has not been well constrained. In this study, a Late Cretaceous (similar to 100 Ma) EW-trending igneous rock belt along the southern margin of the Eurasian continent from the Gangdese terrane to the South China block is recognized based on residual geological records and plate reconstruction. Importantly, these igneous rocks show the characteristics of typical adakites and are consistent with those of adakites derived from partial melting of subducted oceanic crust. Combined with the tectonic evolution of the Neo-Tethys Ocean, ridge subduction was most likely responsible for this adakitic igneous rock belt. In addition, a NS-trending compression event simultaneously occurred in the southern margin of the Gangdese terrane and the South China block during the Late Cretaceous, which agrees well with ridge sub-duction. The identification of the Neo-Tethys ridge subduction is of great significance for understanding the evolution, magmatism and mineralization of the Neo-Tethys tectonic domain.

Late Cretaceous granitoids are developed in the eastern and western districts of the Gejiu ore district, but tin deposits mainly occur in the eastern district, and the reasons for the difference in mineralization between the eastern and western districts are still controversial. Considering the main factors controlling granite Sn fertility, the whole-rock geochemical characteristics of granites on both sides are compared. LA-ICP-MS zircon U-Pb analyses of the Gejiu granites yielded two age periods: the early phase from 79.2 to 83.3 Ma and the later phase from 73.8 to 75.6 Ma. The western district granites have higher zircon εHf(t), CaO/Na2O, Ba, and Sr concentrations and lower Rb/Sr ratios than the eastern district granites, indicating that the western district granites have more mantle-derived materials in the source than the eastern district granites. Results of oxygen fugacity show that the western granites have a higher oxygen fugacity condition. More depleted Ba, Sr, P, Eu and Ti characteristics with obviously negative Eu anomalies in the eastern granites also have high Rb/Sr ratios and low Nb/Ta and Zr/Hf ratios, indicating that the eastern granites experienced highly magmatic differentiation, attributed to high volatile F contents that can reduce the viscosity and solidus of magma. Combined with the differences in field observations and structural styles, on the whole, the western district granites have higher oxygen fugacities and lower F contents and magmatic differentiation than those in the eastern district granites, indicating that the western district granites are not conducive to mineralization.

As a sensitive marker of plate collision events, intraplate compressional deformation can be used to provide a unique regional perspective for the contemporaneous complicated tectonic evolution at the plate margin. Two regional intraplate deformation and uplift events of the late Middle Jurassic and Late Jurassic-Early Cretaceous in the Junggar Basin were revealed through seismic interpretation and geological profiles, and both of them correspond to unconformity in the sedimentary successions. Detrital zircons from Jurassic and Cretaceous strata in the eastern margin of Junggar Basin were selected for LA-ICP MS U-Pb dating. Combined with previous detrital zircon U-Pb dating data, a prominent, time-continuous group of syn-depositional detrital zircons has been discovered in the Jurassic-Cretaceous strata of the Junggar basin, and their discontinuous distribution in the strata above and below the unconformity restricts the precise timing of the corresponding regional intraplate deformation to ca.166-157 Ma and ca.151-129 Ma, respectively, which coincide well with tectono-magmatic events in southern Tibet. Based on previous apatite fission track dating data in Sayan-Siberia orogenic belt and Tianshan-Beishan orogenic belt, we suggest that stages of regional intracontinental deformation in the Junggar Basin and its periphery are related to compressive events on the southern margin of Eurasia. Among them, the first stage of intraplate deformation during ca. 166-157 Ma with shorter duration and slighter intensity may be controlled by the collision of the Karakoram-Lhasa Block with the South Pamir Block and the second during ca.151-129 Ma with longer duration and more intensity may signify the main process of Lhasa and Qiangtang collision and the final full closure of the Bangong-Nujiang Tethys Ocean.

The Fangshan intrusive suite is a composite pluton in the North China Craton that resulted from incremental assembly of small magma batches. The pluton consists of four intrusive units with abundant mafic enclaves. Here we clarify its crystallisation history through zircon U-Pb dating, which indicates prolonged crystallisation of each intrusive unit at upper-crustal levels between 132.5 and 128.7 Ma. The magmas were episodically extracted from a deep storage area and ascended to the final intrusion level at a palaeo-depth of 10-16 km. Zircon trace element and Hf isotopic compositions and Ti-in-zircon temperature of the four intrusive units and mafic enclaves show significant differences and suggest that their crystallisation occurred in isotopically and chemically diverse magma batches. These magma batches formed in the lower crust from the mingling and mixing of various proportions of residual melts, derived from the fractional crystallisation of mafic magmas, with crustal partial melts at high temperatures. Four type of zircons were observed in mafic enclaves based on a simple textural classification, including antecrysts (type 1), xenocrysts (type 2 and type 3), and recrystallised zircon (type 4). Type 1 zircons were not formed at the emplacement level and are "antecrystic", having formed at a deeper, hotter level and been entrained into the ascending melts. Most type 2 zircons were captured from coarse-grained monzonite, and a very small number of grains were sourced from porphyritic granodiorite. Type 3 zircons display a core-rim texture, illustrating that xenocrysts may successively grow in mafic melts. Type 4 zircons display patchy zoning that represents a disequilibrium texture, manifested by the replacement of U-Th-REE-rich zircon by U-Th-REE-poor zircon, which occurred in response to magma mixing between mafic and felsic melts. This study shows that zircon chemistry coupled with detailed textural analyses can provide a powerful tool to elucidate the complex evolution of a magmatic system.

As the product of the amalgamation of multiple microcontinental massifs, Northeast China is located in the easternmost segment of the Central Asian Orogenic Belt (CAOB), which underwent multi-stage tectonic superposition in Mesozoic. Extensive and intensive igneous activities occurred throughout northeast China and the related igneous rocks can be considered as an effective probe for constraining tectonic evolution. In this study, numerous available ages and geochemical data are collected from published literature. The spatial-temporal distribution, rock assemblage, and geochemical characteristics of Mesozoic igneous rocks are systematically reassessed and summarized. A conclusion is drawn that NE China experienced the superposition and transformation of the Paleo-Asian Ocean (PAO) domain, the Mongol-Okhotsk Ocean (MOO) domain, and the PaleoPacific Ocean (PPO) domain in Mesozoic and detailed tectonic evolution is presented as follows. Firstly, NE China was under the joint effect of the MOO and the PAO during Early-Middle Triassic (ca. 252-237 Ma). Arc type igneous rocks in the Erguna-Xing'an Block were induced by the southward subduction of the MOO Plate and adakites with high Sr/Y and (La/Yb)(N) ratios in the south segment of NE China were emplaced in the post collision orogenic environment related to the closure of the PAO. Secondly, during Late Triassic, the influence of the PAO domain was gradually weakened, and igneous activities developed sporadically along the SolonkerXar Moron-Changchun-Yanji suture zone. The MOO continued to subduct south until the Early Jurassic (ca. 220-190 Ma), and continental igneous rocks with arc-like features were widely distributed in the Erguna-Xing'an Block. During ca. 220-200 Ma, the Jiamusi-Khanka Massif was slipped away from the Songnen-Zhangguangcai Range Massif and this progress may be related to the PPO domain. Thirdly, in the Early Jurassic-Early Cretaceous (ca. 200-120 Ma), NE China came under the joint influence of the MOO and PPO tectonic domains. The subduction and closure of the MOO Plate and corresponding thickening of the lower crust resulted in widespread and intensive igneous activities in the Erguna and the Great Xing'an Range (GXAR). Two-stage subduction of the PPO and between which a period of change of subduction direction, induced the two-stage arc igneous activities of ca. 185-164 Ma and ca. 135-120 Ma, and the magmatic hiatus between ca. 163.5-135 Ma in the Zhangguangcai Range (ZGCR) and its east. Fourthly, the influence of the MOO domain was completed at ca. 120 Ma and numerous volcanic rocks corresponding chemically to A-type granite began to erupt violently, due to the rollback of the Paleo-Pacific oceanic slab. Since then, NE China has been completely under the control of the PPO domain.

The Southwest Borneo (SW Borneo) block belongs to Sundaland and is the oldest continental fragment of Borneo that is believed to derive from the Gondwana land. The U-Pb isotopic dating ages of 113 detrital zircons from sandstones of the Ketapang Complex in SW Borneo range from 3 298 Ma to 78 Ma, and show six major age populations: 2 476–2 344 Ma, 2 016–1 831 Ma, 1 296–759 Ma, 455–406 Ma, 262–210 Ma, and 187–78 Ma. The youngest age of these detrital zircons is 78 Ma, indicating that the maximum depositional age of the sandstones is Campanian. Permian-Late Cretaceous detrital zircons are interpreted as having been derived from the nearby Schwaner Mountains and the Permian-Triassic tin belt granitoids in Southeast Asia (SE Asia). Archean-Carboniferous detrital zircons have a continental Gondwana provenance, with their age spectra similar to those of northwestern Australia, indicating that these zircons could be derived from the orogenic belts and cratons in northwestern and central Australia. The provenance of these detrital zircons in this study indicates the SW Borneo block was located on the northwestern margin of Australia during the Paleozoic, in the region of the Banda Embayment. SW Borneo rifted from Australia and moved northward in the Early Jurassic, and this block was added to Sundaland in the Early Cretaceous. The Luconia-Dangerous Grounds continental fragment derived from East Asia collided with SW Borneo after subduction in the Cretaceous, which induced the widespread magmatism in the Schwaner Mountains in SW Borneo.

对5GPa、1500～1750℃条件下柯石英与含水硅酸盐熔体间的微量元素分配行为开展研究.通过高压实验成功合成与大面积硅酸盐熔体共存的大颗粒柯石英晶体（少数情况下有蓝晶石、刚玉共存）,通过扫描电子显微镜和显微拉曼光谱对实验产物进行形貌观察和物相确定,电子探针测定不同相中的主量元素,激光剥蚀电感耦合等离子质谱仪（LA-ICP-MS）分析微量元素.最终,本研究共得到33种元素的分配系数.总体而言,柯石英是一种极其纯净的矿物相;可能除少数元素如Sc、Ti和V外,几乎其他所有元素在柯石英中均表现为不相容.此外,除四价阳离子外的其他所有元素的分配行为都难以用晶格应变模型来解释,这可能暗示着阳离子大小在柯石英与硅酸盐熔体间的微量元素分配过程中起的作用较小.将本研究的结果与文献数据结合,可以观察到温度、压力会对部分元素的分配行为产生影响:温度似乎对不同的微量元素发挥不同的作用,但压力基本上与所有元素的分配系数呈负相关.考虑到柯石英在俯冲的大陆地壳物质中所占比例较大,其可能在某些元素的分配中扮演重要角色,例如Ti元素.

组成大陆地壳的物质主要来自两个地质过程:地幔柱活动和板块俯冲.目前大多数研究认为板块俯冲起始于30多亿年前.在板块俯冲起始之前,基性的初始地壳物质受热重熔是大陆地壳生长的主要方式,其中,地幔柱活动是关键.地幔柱不仅向地壳输送玄武质岩浆,同时导致已有玄武质岩石和沉积岩通过部分熔融向中酸性岩石转化.当原始岩石圈强度足够大时,地幔柱会导致岩石圈倾斜、破裂,产生下滑力,诱发板块俯冲.板块俯冲引发岩浆活动,产生大量的岩浆岩,如岛弧安山岩、弧后盆玄武岩等.这些岩浆岩通过喷发、侵位,再经由块体拼贴、增生等过程加入到大陆地壳,是大陆地壳生长的主要途径.同时,板内岩浆活动乃至地幔柱活动等也与板块俯冲有直接或者间接的联系.俯冲再循环物质促进地幔柱发育,也为大陆地壳的生长提供物源和热能.与此同时,大陆地壳不断风化剥蚀,其中一部分沉积物随俯冲板块再循环到地幔,而板块俯冲过程也通过俯冲剥蚀等过程,将仰冲盘岩石圈物质刮削带入地幔.这些是大陆地壳消减的主要途径.目前大陆地壳增生和消减基本处于动态平衡.

Trace element partitioning between coesite and hydrous silicate melt has been investigated at 5 GPa and 1500−1750°C. High-P experiments successfully produced large coesite crystals in equilibrium with large silicate melt pools (plus kyanite and corundum crystals in some cases). Scanning electron microscopy and micro-Raman spectroscopy were employed to characterize the phases and the textures. Wavelength-dispersive electron microprobe analyses were performed to quantify conventional major elements, and laser ablation-inductively coupled plasma-mass spectrometry analyses were successfully conducted to quantify trace elements. Eventually, high-P partition coefficients were obtained for 33 elements. In general coesite is a very pure phase. With a few possible exceptions like Sc, Ti, and V, nearly all other trace elements are incompatible in coesite. Moreover, the partitioning behaviors of nearly all trace elements except some 4+ cations cannot be readily described by the lattice strain model, presumably implying a minor role for the cation size in the trace-element partitioning. Combining our experimental results with the results in the literature, some T and P effects on the element partitioning behavior have been observed: T seemingly has different effects on different trace elements, but P might negatively correlate with the partition coefficients in all cases. Due to its large modal fraction in some subducted materials such as the continental crustal material, coesite might play an important role in the distributions of some trace elements, Ti for example.

For sandstone-type uranium deposits, an unobstructed recharge-runoff-discharge (RRD) groundwater system strongly constrained by tectonic events is one of the most important cornerstones for uranium mineralization. Junggar Basin, located in NW China, is proposed to be an intracontinental Mesozoic basin with great sandstonetype uranium metallogenic potential but no large uranium deposits so far. Compared with other uranium-bearing basins in Northern China, the Junggar Basin experienced episodic strong tectonic events in the Meso-Cenozoic era, resulting in more intense stratigraphic deformation and dislocation, so the detailed analysis of tectonic evolution and ore-controlling structures is indispensable to deciphering the uranium mineralization process in the region. This study interprets the seismic profiles and analyzes the apatite fission track (AFT) thermochronological signatures of the Jurassic Toutunhe Formation detrital sediments in the eastern Junggar Basin, which reveals that the Junggar Basin experienced four tectonic events: the Middle Triassic-Early Jurassic episodic uplift of basin margin (ca. 240-180 Ma), the Late Jurassic or Early Cretaceous modest deformation and uplift within the basin (ca. 140 Ma), the Late Cretaceous-Paleocene rapid uplift (ca. 100-60 Ma), the Eocene-Present episodic rapid uplift (ca. 38-0 Ma). On this basis, the tectonic couples comprising tectonic window and structural pattern is dissected. The ore-controlling structures that can build the good RRD system are identified, such as Jurassic slope in the eastern Luliang Uplift, Jurassic hanging wall of fault propagation fold, Neogene foredeep of the foreland basin, and so on. Meanwhile, the rapid uplifts in ca.100-60 Ma and ca.38-0 Ma are ascertained as the key tectonic events constrained uranium mineralization. Afterward, a uranium metallogenic model based on the thread of basin tectonic evolution is established, which is of great significance for further deployment of uranium exploration in the basin.

Antimony is a chalcophile element, which is easily combined with sulfur. The abundances of antimony in the core (0. 14 x 10(-6)), the mantle (0. 006 x 10(-6)) and the crust (0. 02 x 10(-6)) are all very low, while it is enriched in black shale (5. 0 x 10(-6)). The solubility of antimony is controlled by temperature, salinity, pH value and oxygen fugacity, but not to pressure. Rutile and omphacite are the main carriers of antimony in high-pressure to ultrahigh-pressure metamorphic rocks. Antimony is also a typical low-temperature metallogenic element. The low-temperature mineralization domain in South China, possesses 60% of the world's proven antimony reserves mostly formed in the Yanshanian Period. Our studies show that the mineralization of Sb mainly experienced two stages : One is the supergene process related to weathering and sedimentation, and the other is the hydrothermal process caused by magmatism. South China, located near the equator during the Cambrian, was affected by the Gondwana continental orogenic belt, and it is one of the most weathered areas in the world. The fertile source area is very important for the formation of antimony deposits in South China, whereas organic matter plays a positive role for the extraction and migration of antimony. As a result of Neoproterozoic Oxidation Event, antimony was oxidized to water-soluble SbO3- during supergene weathering. The organic matter, produced by the Ediacara biota is conducive to extracting antimony from water, and precipitating it in reduced sediments (black shale). The Mesozoic magmatic activity in South China baked the surface antimony-rich Cambrian black shale, and the ore-forming fluids produced by magma migrated upward, leaching Sb from black shales or mixing with other ore-forming fluids produced by metamorphic dehydration or melting of the black shale; and then it was transported to a favorable location far from the rock mass to deposit, eventually forming a large-scale antimony ore belt in South China.

Titanium, because of its high strength and corrosion resistance, has been widely used in aerospace, medicine, mobile phone and other fields. It is a strategic metallic element in the 20th century. In nature, ilmenite, titanomagnetite and rutile are the most economical titaniferous minerals. Titanium was initially considered to be an inactive metallic element, however, more and more evidences support that it can migrate into metamorphic hydrothermal fluids in certain conditions. The presence of rutile and apatite as paragenetic minerals in high-pressure metamorphic veins may be due to the influence of F-rich fluids on the migration and enrichment of Ti. When fluorapatite precipitates from the F-rich fluids, the K6TiF6 complex will decompose, therefor the solubility of Ti will decrease and rutile will crystallize, which is probably the mechanism of metamorphism and enrichment of the metamorphic rutile deposit. In the magmatic deposits, titanium is often associated with magnetite deposits. It is generally believed that the degree of partial melting, volatile content and the temperature of ore-forming magma determine the formation Ti-bearing deposits or high Ti intrusions. This paper considers that the remelting of recycling rutile-rich oceanic crust or Ti-rich sedimentary deposits is the important source of ore-forming materials for magmatic-type titanium deposits. The formation of sedimentary titanium deposits are related to regional geology, physiography and hydrodynamics. They are often located on the passive continental margin, with high weathering, high-grade titanium sources through weathering, denudation and transgression, and are mainly formed along the costal zone, especially between the low latitudes of 30 degrees N and 30 degrees S. In conclusion, the successful mineralization of Ti is determined by the Ti-rich sources, the depth of provenance, the temperature and degree of partial melting, the degree of contamination of the continental crust, volatile content, the ability of weathering and denudation, etc.

Mafic microgranular enclaves (MMEs) are commonly formed during magma mixing and usually record contrasting physicochemical diagenetic characteristics relative to their host rocks. We present a finding that some MMEs from the Cretaceous Qianjia pluton, which is believed to be the product of magma mixing, exhibit diagenetic conditions analogous to those of their host granites. Integrated calculations based on in situ compositions of minerals (e.g., zircon, titanite, amphibole, feldspar, and apatite) from the Qianjia monzonitic MMEs and their host granites indicate that they exhibit similar diagenetic temperatures (700-800 degrees C) and pressures (0.20-028 GPa), but discrepant oxygen fugacity and water activity. The MMEs have higher oxygen fugacity and water activity, as well as lower Th/U ratios, compared to the host granites, suggesting more oxidized and H2O-rich circumstances. Besides, high F concentrations and F/Cl ratios in apatites from both the MMEs and host granites and their parent magma indicate a relatively F-rich magma source that was probably derived by F-bearing mineral dehydration during plate subduction. Similar physicochemical diagenetic conditions between the MMEs and their host granites seemingly reveal their cognate features; however, slight differences in the oxygen fugacity, water activity, and chemistry of certain minerals (e.g., apatite and titanite) provide clues on magma mixing. We therefore propose that the MMEs involved might have been derived from local heterogeneous hybrid melts or by early crystallization during a post-mixing process. In this case, information about the magma mixing has been almost eliminated due to the geochemical re-equilibration. Therefore, in the case of magma-mixing derived intrusions, the MMEs could be formed not only during magma mixing but also during a post-mixing stage, in which certain minerals most likely preserved a few geochemical characteristics of magma mixing. (C) 2020 Elsevier B.V. All rights reserved.