Explore the vast range of titles available.

As the exploration and drilling of oil, natural gas and geothermal wells are expanding continuously, research into high-efficiency rock drilling technology is imperative. High-voltage electro pulse boring (EPB) has the advantages of high rock breaking efficiency and good wall quality, and is a new and efficient potential method of rock breaking. The design of electrode drill bits and the selection of drilling process parameters are the main obstacles restricting the commercialization of EPB. Accordingly, it is necessary to determine the influences on high-voltage EPB. In this study, based on the equivalent circuit of high-voltage electro pulse breakdown, a mathematical model of high-voltage electro pulse discharge in rock is established. Meanwhile, a numerical simulation model of high-voltage EPB of hard granite is established based on a coaxial cylindrical electrode structure, which is often used for electrode drill bits. The simulation analysis software Comsol Multiphysics (Comsol Multiphysics®5.3a, COMSOL Co., Ltd., Stockholm, Sweden) is used to study the influences of granite composition, electrode spacing and electrode shape on the high-voltage EPB process. In addition, the influences of electrical parameters on high-voltage EPB are calculated according to a model of high-voltage electro pulse discharge in rock. Finally, it is demonstrated that high-voltage EPB is influenced by granite composition, electrical parameters, electrode spacing, and electrode shape, and the relationships between these factors are obtained. This study is of guiding significance for improving rock breaking efficiency, reducing energy loss, designing electrode drill bits and selecting drilling process parameters.

Ferro-ferri-holmquistite (IMA2022-020), ideal formula â¡Li.sub.2 (Fe32+Fe23+)Si.sub.8 O.sub.22 (OH).sub.2, was found in albitized granite from the Iwagi islet, Ehime, Japan. Ferro-ferri-holmquistite is a .sup.C Fe.sup.2+ Fe.sup.3+ analogue of holmquistite and belongs to the lithium-subgroup amphiboles. It commonly occurs as acicular aggregate and/or isolated crystals in quartz, albite and K-feldspar and is blue with a bluish-grey streak and a vitreous luster. It has a Mohs hardness of 5 1/2. Its cleavage is perfect on 210. Measured and calculated densities are Dmeas.=3.2 g cm.sup.-3 and Dcalc.=3.317 g cm.sup.-3, respectively. Ferro-ferri-holmquistite is optically biaxial (-), with α=1.685, β=1.713 and γ=1.727, and is pleochroic, with X= pale blue â¼ pale yellowish blue, Y= deep blue â¼ brownish blue and Z= deep blue â¼ deep bluish violet; XZY. The magnetic susceptibility is similar to the associated biotite. Ferro-ferri-holmquistite is insoluble in HCl, HNO.sub.3 and H.sub.2 SO.sub.4 . The empirical formula calculated on the basis of Σ(C+T) = 13 on the results obtained by electron microprobe analyzer (EPMA), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is .sup.A (K.sub.0.01 Na.sub.0.06).sub.Σ0.07 .sup.B (Li.sub.1.95 Na.sub.0.04 Ca.sub.0.01).sub.Σ2.00 .sup.C (Fe2.822+Fe1.393+Al.sub.0.51 Mg.sub.0.22 Mn0.052+Ti.sub.0.01).sub.Σ5.00 .sup.T (Si.sub.7.98 Al.sub.0.02).sub.Σ8.00 O.sub.22 (OH).sub.1.94 F.sub.0.06 . Structure refinement converged to R.sub.1 = 4.22 %. The space group is orthorhombic Pnma, and the unit-cell parameters are a= 18.5437(2) Ã, b= 17.9222(1) Ã, c= 5.3123(1) à and V= 1765.51(1) Ã.sup.3 . Based on the refined site occupancies, the structural formula can be written as .sup.A Na.sub.0.062 .sup.M4 (Li.sub.1.952 Na.sub.0.048).sub.Σ2.000 .sup.M1 (Fe1.7702+Mg.sub.0.230).sub.Σ2.000 .sup.M2 (Fe1.4463+Fe0.1022+Al.sub.0.452).sub.Σ2.000 .sup.M3 (Fe0.8912+Mg.sub.0.109).sub.Σ1.000 .sup.T Si.sub.8 O.sub.22 (OH).sub.2 (Z= 4). Three OH-stretching IR bands, centered at 3614, 3631 and 3644 cm.sup.-1, are assigned to the local configuration M1M1M3= FeFeFe, MgFeFe (including FeMgFe and FeFeMg) and MgMgFe (including MgFeMg and FeMgMg), respectively, based on the IR studies of the orthorhombic Pnma amphiboles.

Distinctive magmatic-hydrothermal, tourmaline-rich features have developed in the Heemskirk and Pieman Heads granites from western Tasmania, Australia. They are categorized as tourmaline-rich patches, orbicules, cavities, and veins, based on their distinctive morphologies, sizes, mineral assemblages, and contact relationships with host granites. These textural features occur in discrete layers in the roof zone of granitic sills within the Heemskirk and Pieman Heads granites. Tourmaline patches commonly occur below a tourmaline orbicule-rich granitic sill. Tourmaline-filled cavities have typically developed above the tourmaline-quartz orbicules in the upper layer of the white phase of the Heemskirk Granite. Tourmaline-quartz veins penetrate all exposed levels of the granites, locally cutting tourmaline orbicules and cavities.The tourmalines are mostly schorl (Fe-rich) and foitite, with an average end-member component of schorl45 dravite6 tsilaisite1 uvite0 Fe-uvite3 foitite31 Mg-foitite4 olenite10 Element substitutions of the tourmalines are controlled by FeMg-1, YAlX∎(R2+Na)-1, and minor YAlO(R2+OH)-1 (where R2+ = Fe2+ + Mg2+ + Mn2+) exchange vectors. Several trace elements in tourmaline have consistent chemical evolutions grouped from tourmaline patches, through orbicules and cavities, to veins. There is a progressive decrease of most transition and large ion lithophile elements, and a gradual increase of most high-field strength elements. These compositional variations in the different tourmaline-rich features probably relate to element partitioning occurring in these phases due to volatile exsolution and fluxing of aqueous boron-rich fluids that separated from the granitic melts during the emplacement of S-type magmas into the shallow crust (4 to 5.5 km).Tourmalines from the Heemskirk Granite are enriched in Fe, Na, Li, Be, Sn, Ta, Nb, Zr, Hf, Th, and rare earth elements relative to the tourmalines from the Pieman Heads Granite, but depleted in Mg, Mn, Sc, V, Co, Ni, Pb, Sr, and most transition elements. These results imply that bulk compositions of the host granites exert a major control on the chemical variations of tourmalines. The trace element compositions of tourmalines from the Sn-mineralized Heemskirk Granite are different from those of the barren Pieman Heads Granite. Trace element ratios (e.g., Zn/Nb, Co/Nb, Sr/Ta, and Co/La) and Sn concentrations in tourmaline can distinguish the productive Heemskirk Granite from the barren Pieman Heads Granite.

The Dahutang tungsten deposit, located in the Yangtze Block, South China, is one of the largest tungsten deposits in the world. Tungsten mineralization is closely related to Mesozoic granitic plutons. A drill core through a pluton in the Dalingshang ore block in the Central segment of the Dahutang tungsten deposit shows that the pluton is characterized by multi-stage intrusive phases including biotite granite, muscovite granite, and Li-mica granite. The granites are strongly peraluminous and rich in P and F. Decreasing bulk-rock (La/Yb)N ratios and total rare earth element (ΣREE) concentrations from the biotite granite to muscovite granite and Li-mica granite suggest an evolution involving the fractional crystallization of plagioclase. Bulk-rock Li, Rb, Cs, P, Sn, Nb, and Ta contents increase with decreasing Zr/Hf and Nb/Ta ratios, denoting that the muscovite granite and Li-mica granite have experienced a higher degree of magmatic fractionation than the biotite granite. In addition, the muscovite and Li-mica granites show M-type lanthanide tetrad effect, which indicates hydrothermal alteration during the post-magmatic stage. The micas are classified as lithian biotite and muscovite in the biotite granite, muscovite in the muscovite granite, and Li-muscovite and lepidolite in the Li-mica granite. The Li, F, Rb, and Cs contents of micas increase, while FeOT, MgO, and TiO2 contents decrease with increasing degree of magmatic fractionation. Micas in the muscovite granite and Li-mica granite exhibit compositional zonation in which Si, Rb, F, Fe, and Li increase, and Al decreases gradually from core to mantle, consistent with magmatic differentiation. However, the outermost rim contains much lower contents of Si, Rb, F, Fe, and Li, and higher Al than the mantle domains due to metasomatism in the presence of fluids. The variability in W contents of the micas matches the variability in Li, F, Rb, and Cs contents, indicating that both the magmatic and hydrothermal evolutions were closely associated with W mineralization in the Dahutang deposit. The chemical zoning of muscovite and Li-micas not only traces the processes of W enrichment by magmatic differentiation and volatiles but also traces the leaching of W by the fluids. Therefore, micas are indicators not only for the magmatic-hydrothermal evolution of granite, but also for tungsten mineralization.

Granite is one of the most important components of the continental crust on our Earth; it thus has been an enduring studied subject in geology. According to present knowledge, granite shows a great deal of heterogeneity in terms of its texture,structure, mineral species and geochemical compositions at different scales from small dike to large batholith. However, the reasons for these variations are not well understood although numerous interpretations have been proposed. The key point of this debate is whether granitic magma can be effectively differentiated through fractional crystallization, and, if so, what kind of crystallization occurred during the magmatic evolution. Although granitic magma has high viscosity because of its elevated SiO2 content, we agree that fractional crystallization is effectively processed during its evolution based on the evidence from field investigation,mineral species and its chemical variations, and geochemical compositions. These data indicate that crystal settling by gravitation is not the only mechanism dominating granitic differentiation. On the contrary, flow segregation or dynamic sorting may be more important. Accordingly, granite can be divided into unfractionated, fractionated（including weakly fractionated and highly fractionated） and cumulated types, according to the differentiation degree. Highly fractionated granitic magmas are generally high in primary temperature or high with various volatiles during the later stage, which make the fractional crystallization much easier than the common granitic melts. In addition, effective magmatic differentiation can be also expected when the magma emplaced along a large scale of extensional structure. Highly fractionated granitic magma is easily contaminated by country rocks due to its relatively prolonged crystallization time. Thus, granites do not always reflect the characteristics of the source areas and the physical and chemical conditions of the primary magma. We proposed that highly fractionated granites are an important sign indicating compositional maturity of the continental crust, and they are also closely related to the rare-elemental（metal） mineralization of W,Sn, Nb, Ta, Li, Be, Rb, Cs, REEs, etc.

Silica-rich granites and rhyolites are components of igneous rock suites found in many tectonic environments, both continental and oceanic. Silica-rich magmas may arise by a range of processes including partial melting, magma mixing, melt extraction from a crystal mush, and fractional crystallization. These processes may result in rocks dominated by quartz and feldspars. Even though their mineralogies are similar, silica-rich rocks retain in their major and trace element geochemical compositions evidence of their petrogenesis. In this paper we examine silica-rich rocks from various tectonic settings, and from their geochemical compositions we identify six groups with distinct origins. Three groups form by differentiation: ferroan alkali-calcic magmas arise by differentiation of tholeiite, magnesian calc-alkalic or calcic magmas form by differentiation of high-Al basalt or andesite, and ferroan peralkaline magmas derive from transitional or alkali basalt. Peraluminous leucogranites form by partial melting of pelitic rocks, and ferroan calc-alkalic rocks by partial melting of tonalite or granodiorite. The final group, the trondhjemites, is derived from basaltic rocks. Trondhjemites include Archean trondhjemites, peraluminous trondhjemites, and oceanic plagiogranites, each with distinct geochemical signatures reflecting their different origins. Volcanic and plutonic silica-rich rocks rarely are exposed together in a single magmatic center. Therefore, in relating extrusive complements to intrusive silica-rich rocks and determining whether they are geochemically identical, comparing rocks formed from the same source rocks by the same process is important; this classification aids in that undertaking.

The Nuweibi albite granite (NAG) is a postcollisional intrusion emplaced as a high-level magmatic cupola into metamorphic and syntectonic calc-alkaline country rocks. It consists of two cogenetic intrusive bodies: the western, nonporphyritic, albite granite was emplaced deeper than the eastern, fine-grained, porphyritic, albite granite. In places the nonporphyritic phase crosscuts the earlier porphyritic phase, but the occurrence of gradational contacts between the phases implies a near coincidence in time, with the nonporphyritic phase emplaced before crystallization of the porphyritic phase was complete. The steeply dipping slope of the western contact of the Nuweibi pluton against country rocks, in contrast to the gently dipping contacts above the eastern and northeastern parts, indicates the probable location of the cupola apex in the eastern part of the pluton. The NAG intrusion is highly evolved meta- to peraluminous leucocratic rare-metal albite granite. The NAG intrusion is chemically zoned, with upward increases of Al2O3, Na2O, Sr, Ga, and Ta concentrations, alongside upward decreases in SiO2, K2O, Rb, Nb, Zn, Zr, Th, Sn, and rare earth element concentrations. These trends are interrupted by a compositional gap with discontinuities in evolutionary trends of both compatible and incompatible elements, suggesting multiple pulses of intrusion. The NAG was generated via partial melting of a juvenile crust that had undergone extensive fractional crystallization combined with late-magmatic fluid overprint. Accumulation of residual volatile-rich melt and exsolved fluids in the apical part of the magmatic cupola produced stockscheider pegmatite, greisen, and quartz veins that cut the peripheries of the NAG pluton. Metasomatic activity by late- to postmagmatic fluids drove changes in the bulk composition of the cupola, removing K and driving the alkali feldspars toward pure albite.

The Shimensi deposit (South China) is a newly discovered W-Cu-Mo polymetallic deposit with a reserve of 0.76 million tones WO3, one of the largest tungsten deposits in the world. We report elemental and Sr-Nd isotopic data for scheelites from the giant deposit, to determine the source region and genesis of the deposit. Scheelite is the most important ore mineral in the Shimensi deposit. Trace elements (including REEs) and Nd-Sr isotopic compositions of scheelites were used to constrain the origin of the mineralizing fluids and metals. Our data reveal that the REEs of scheelite are mainly controlled by the substitution mechanism 3Ca2+ = 2REE3++ ∎Ca, where ∎Ca is a Ca-site vacancy. Scheelites from the Shimensi deposit show negative Eu anomalies in some samples, but positive Eu anomalies in others in the chondrite-normalized REE patterns. The variation of Eu anomalies recorded the ore-forming processes. Considering the close spatial and temporal relationship between the mineralization and porphyritic granite, we think the negative Eu anomalies were inherited from the porphyritic granite and the positive ones from destruction of plagioclase of country rock during fluid-rock interaction. The variation of cathodeluminescence (CL) color of a single scheelite from red to blue and to yellow was likely associated with the increase of REE contents. The scheelites hosted in the Mesozoic porphyritic granite with negative Eu anomalies formed in a primitive ore-forming fluid, whereas the scheelites hosted in Neoproterozoic granite with positive Eu anomalies precipitated in an evolved ore-forming fluid. The high Nb, Ta, LREE contents, and LREE-enriched REE patterns of scheelites from the Shimensi deposit reveal a close relationship with magmatic hydrothermal fluids. The scheelites from the Shimensi deposit are characterized by low εNd(t) values (-6.1 ∼ -8.1) and unusually high and varied initial 87Sr/86Sr ratios (0.7230∼0.7657). The εNd(t) values of scheelites are consistent with those of the Mesozoic porphyritic granite, but the Sr isotopic ratios are significantly higher than those of the granites, and importantly, beyond the Sr isotopic range of normal granites. This suggests that the ore-forming fluids and metals cannot be attributed to the Mesozoic porphyritic granites alone, the local Neoproterozoic Shuangqiaoshan Group schists/gneisses with high Rb/Sr ratios and thus radiogenic Sr isotopic compositions should have contributed to the ore-forming fluids and metals, particularly, in a later stage of ore-forming process, by intense fluid-rock interaction. This is different from a commonly accepted model that the ore-forming fluids and metals were exsolved exclusively from the granite plutons.

Granite genesis is crucial to understanding the evolution of continental crust, yet many concerns about granite genesis remain not well answered, such as whether I-type granite contains metasedimentary components, what controls granite compositional diversity, and how granitic plutons are constructed. To explore these issues, we conducted a detailed study on the two-mica plagiogranite, tonalite, and biotite plagiogranite units of the Wujinxia composite pluton in the eastern Qilian orogen, NE Tibetan Plateau. These units comprise two-mica plagiogranite, tonalite (with diorite enclave), and biotite plagiogranite. Zircon U–Pb data reveal that three granitic units formed at ~ 487 Ma, ~ 464 Ma, and ~ 430 Ma, respectively. Magmatic and xenocrystic garnet were identified from the tonalite and biotite plagiogranite, respectively. The two-mica plagiogranite, tonalite, and biotite plagiogranite all belong to low-K series rocks (K 2 O/Na 2 O = 0.10–0.26), and were derived from deep crustal sources mainly consisting of juvenile mafic rocks, with involvement of minor metasedimentary rocks in the magma sources of the two-mica plagiogranite and tonalite. The diorite enclave within the tonalite was probably derived from an enriched mantle-derived basaltic magma. Mineral compositions, thermobarometric calculations, and whole-rock geochemical data indicate that the low-K intrusive units of the Wujinxia composite pluton resulted from multiple magmatic systems at different depths. The results suggest that I-type granites can contain metasedimentary components by partial melting of a mixed crustal source, and high-Mn content helps the preservation of high-Ca garnet within such rocks. For a composite pluton spanning a large compositional variation, its compositional diversity is jointly controlled by magma source composition, melting condition and thermal evolution of individual magma pulses, and the resulted assembly style during pluton construction. Graphical abstract

Hydrothermal alteration records fluid–rock interactions and can therefore be used to constrain element migrations during mineralization. Although hydrothermal alteration is widely developed in hydrothermal vein-type uranium deposits in South China, consideration of elemental mass changes during alteration has not been examined. The Egongtang uranium deposit in the central Nanling Range is mainly hosted by the Qingzhangshan granite in South China, and was strongly altered by K-feldspar, quartz, chlorite, illite, haematite, pyrite and carbonates. The alteration section can be divided into five horizontal zones: fresh granite (Zone V), a distal alkaline alteration zone (Zone IV), a chlorite-rich zone (Zone III), a close-to-ore sericite/illite alteration zone (Zone II) and a central mineralization zone with strong haematitization (Zone I). Whole-rock geochemistry of the altered samples indicates that from Zone IV to Zone I, the content of SiO2 and U increases significantly. The mass gains of SiO2, MgO and Fe2O3 were proportional to the concentration of U. The content of trace elements (such as Ba, K, La, Ce, Pr, Sr, P, Eu, etc.) gradually decreases from Zone V to Zone I. The rare earth elements manifest a decrease in light rare earth elements and a slight increase in heavy rare earth elements accordingly from Zone V to Zone I. This study shows that the ore materials of the Egongtang deposit were mainly derived from the Qingzhangshan granites. In the early alkali alterations, large amounts of U were partitioned into the fluids. In the ore-forming stage, ores precipitated accompanied by acid metasomatism such as chloritization, haematitization and carbonation.