Fangyang Hu

Spodumene [LiAl(Si ₂ O ₆ )], as an important Li source, is crucial for sustaining the global Li supply. Lithium isotopes have been a powerful geochemical tracer for unravelling magmatic‐hydrothermal processes within pegmatite systems. In this study, we systematically evaluated the analytical precision and accuracy of fs‐LA‐MC‐ICP‐MS measurement results for Li isotopes in spodumene samples, with particular emphasis on the accuracy issues arising from non‐matrix‐matched calibration. Compared with glass materials (low‐Li samples), the signal‐matching issue is less significant for spodumene with analytical accuracy within 1.0‰ when the signal‐matching degree ranges from 50% to 300%. Matrix effects between NIST SRM 610 glass and spodumene were found, leading to a ~4.0‰ systematic offset, suggesting that matrix‐matched calibration is necessary for accurate Li isotope determination in spodumene samples. With the refined protocol, the analytical precision and accuracy were better than 1.0‰. Three natural spodumene samples (DHLTan, KKTH and LJG) were characterised as reference materials for in situ Li isotope ratio determination. The three materials have homogeneous δ ⁷ Li values as revealed by multiple fs‐LA‐MC‐ICP‐MS analyses ( n = 90) in two different measurement sessions. The recommended δ ⁷ Li values were determined in two or three independent solution MC‐ICP‐MS laboratories, and yielded δ ⁷ Li values (relative to L‐SVEC) of 1.01 ± 0.46‰ for LJG, 2.69 ± 0.63‰ for DHLTan and 3.63 ± 0.43‰ for KKTH. We applied this technique to the Lhozhag pegmatite‐type Li deposit, and two types of spodumene were identified with first and second stages having δ ⁷ Li values of ~ ‐6.2‰ and ~ ‐7.5‰, indicating different sources (i.e., hydrothermal fluids).

Understanding how tectonic uplift and drainage reorganization controlled sediment dispersal during the Cretaceous is critical for reconstructing the topographic evolution of southeast China. This study examines how sediment sources and routing systems evolved during the Cretaceous, using the Danxia Basin as a key archive and adjacent basins for regional comparison. We integrate sedimentological observations, detrital zircon U‐Pb‐Hf isotopic data, whole‐rock Pb isotope geochemistry and source unmixing results from the Danxia Basin deposits, together with published Jurassic to Paleogene zircon age data sets from nine adjacent basins. The results reveal a regional provenance shift from dominant northern cratonic sources (North China and Yangtze blocks) during the Jurassic to increasing Cathaysian sources during the Cretaceous, including the Wuyishan and Yunkai terranes and the Nanling Tectonic Belt. Within the Danxia Basin, Cretaceous lithologies record a two‐stage provenance evolution: Early Cretaceous sediments mainly derived from the Wuyishan Terrane, whereas Late Cretaceous deposits show mixed input from the Yunkai Terrane, Nanling Tectonic Belt and Wuyishan Terrane, reflecting drainage expansion and/or sediment‐routing reorganization. Published thermochronological data indicate enhanced uplift and exhumation in the Yunkai Terrane and Nanling regions during the Late Cretaceous, driving increased sediment flux to both inland and coastal basins. During the Paleocene‐Eocene, sediment supply became increasingly dominated by the Nanling region as exhumation in Yunkai region waned. These observations support a dynamic “seesaw” topographic model, in which alternating uplift of northern cratonic and eastern Cathaysian source regions governed sediment dispersal, basin architecture and paleoenvironmental evolution across southeast China.

铷(Rb)作为关键稀有金属,在航空航天、电子工业、医疗健康以及现代能源等领域具有不可替代的应用价值。铷具有强分散性,难以形成独立矿物和独立矿床,主要伴生于稀有金属花岗岩和伟晶岩中。富铷的矿物主要为锂云母、铁锂云母和天河石,其中锂云母是最主要的工业矿物。因此,明确铷在花岗岩-伟晶岩中赋存状态及其富集成矿的关键控制因素,对于指导其找矿勘查、实现资源高效利用至关重要。本文梳理了我国主要花岗岩型和伟晶岩型铷矿床的研究成果,从矿化类型、全岩成分及云母成分角度,系统分析铷的富集特征与控制因素,并探讨了喜马拉雅造山带的铷矿化特征与潜力。通过总结分析,我们认为影响富铷矿物类型的因素主要包括岩浆源区成分、岩浆结晶分异程度以及熔体-流体相互作用。相比于变质火成岩或杂砂岩,泥质岩石作为源区形成的岩浆,由于其铝饱和指数相对较高,铷更易赋存于云母中。随着岩浆的分异演化,铷通常同时赋存于钾长石和云母中,而强烈熔体-流体相互作用可以使得钾长石转变为钠长石,并使得长石中的Rb进入云母,促进Rb在云母中富集。虽然不同铷成矿点的云母成分受岩浆源区差异的影响,表现出明显不同的特征,但是岩浆源区的新生或古老并不影响铷的富集成矿。相比于源区,岩浆的高程度分异演化是控制铷富集成矿的首要因素,而相对封闭的岩浆体系是促进岩浆发生高程度分异演化和形成云母型铷矿的关键。目前来看,花岗岩型铷矿普遍拥有伟晶岩壳,而具有良好内部分带的伟晶岩,其云母的铷富集程度和规模通常大于区域分带伟晶岩,这反映了局部的封闭作用对岩浆分异和挥发分的富集具有重要影响。近年来,喜马拉雅造山带发现存在天河石型和锂云母型铷矿化。然而,相比于全国其他主要铷矿点,喜马拉雅带内花岗岩和伟晶岩的云母具有相对贫Rb富Cs的特征,并且喜马拉雅伟晶岩以区域分带为主,内部分带较弱,导致喜马拉雅地区的铷矿化存在一定"先天不足"。但是,目前喜马拉雅带内铷矿化点广泛分布,这可能与藏南拆离系控制下的熔体高效抽提过程有关,这促进了岩浆发生较高程度的分异演化。相比于铷,喜马拉雅带内的铯富集具有一定"先天优势",具有较好的矿化前景。

高纯石英是我国最新公布确认的矿种, 理解其形成机制和主控因素对于未来寻找相关资源至关重要。然而, 目前关于其成因机制的研究仍较为匮乏, 对于何种地质条件有利于高纯石英的形成尚存争议。本文以华北克拉通北缘三木代庙地区花岗岩和伟晶岩中的石英作为研究对象, 探讨花岗岩-伟晶岩演化过程和变形作用对石英中微量元素含量的影响, 并对该地区的高纯石英成矿潜力进行初步厘定。本研究的主要研究对象包括未变形二云母花岗岩、变形二云母花岗岩、未成矿伟晶岩及锂辉石-锂云母成矿伟晶岩中的石英。分析结果显示, 不同类型岩石的石英微量元素组成差异显著, 主要受控于岩浆性质、分异程度及结晶物理条件。二云母花岗岩石英整体Ti和Al含量较高, 超出高纯石英相关标准(Al < 30×10^-6, Ti < 10×10^-6), 而Li含量则基本达到高纯石英的标准(Li < 5×10^-6), 这与岩浆相对较高的温度和较低的演化程度有关, 而Al的富集则可能与围岩混染关系密切。相比于未变形二云母花岗岩, 变形二云母花岗岩的石英Li含量显著偏低, 但Al和Ti含量则变化有限, 表明变形作用对该地区石英的纯化有一定促进作用。由于伟晶岩的岩浆演化程度高并伴随流体活动, 导致其中石英的Li、Al和Ge含量普遍较高, 远超高纯石英标准。相比于锂成矿伟晶岩, 未成矿伟晶岩的杂质含量整体低于成矿伟晶岩, 而成矿伟晶岩的边部带(块体长石带和层状细晶岩带)杂质相对核部偏低。由此, 对于伟晶岩而言, 低演化的伟晶岩边部可能为形成高纯石英的有利部位, 而核部因高岩浆演化程度和强流体活动导致其杂质元素含量偏高。综上, 低温、低演化、低混染并伴随后期变形作用是形成高纯石英的有利条件。三木代庙地区目前花岗岩-伟晶岩的石英整体不满足高纯石英要求, 但考虑到该地区与东秦岭、阿勒泰等已知存在高纯石英的地区地质条件具有一定相似性, 该地区局部可能具有高纯石英的找矿潜力, 其成矿条件有待进一步系统分析。

The redox state of arc mantle has been considered to be more oxidized and diverse than that of the mid-ocean ridge, but the cause of the variation is debated. We examine the redox state of the Cenozoic global arc mantle by compiling measured/calculated fO₂ of olivine-hosted melt inclusions from arc magma and modeled fO₂ based on V/Sc and Cu/Zr ratios of arc basaltic rocks. The results indicate that the redox state of Cenozoic arc mantle is latitude dependent, with less oxidized arc mantle in the low latitudes, contrasting with a near constant across-latitude trend in the mid-ocean ridges. We propose that such a latitude-dependent pattern in the arc mantle may be controlled by the variation in the redox state of subducted sediment, possibly related to a latitudinal variation in the primary production of phytoplankton, which results in more organic carbon and sulfide deposited on the low-latitude ocean floor. Our findings provide evidence for the impact of the surface environment on Earth’s upper mantle.

近年来，喜马拉雅稀有金属成矿的研究与找矿工作不断取得突破，使得喜马拉雅地区成为我国重要的稀有金属成矿带。本文报道了希夏邦马峰地区新发现的锂辉石伟晶岩，发现地位于吉隆岩体东北侧的岗布地区，与吉隆扎龙沟隔山相望。这是在吉隆岩体附近首次发现锂辉石伟晶岩露头，是继琼嘉岗(普士拉)锂辉石伟晶岩、嘎波锂辉石伟晶岩、热曲锂辉石伟晶岩和库曲锂辉石伟晶岩之后，又一锂成矿发现点。结合已有研究显示吉隆扎龙沟地区具有极高的岩浆分异演化程度，表明吉隆岩体北侧具有很好的稀有金属成矿前景。该成矿伟晶岩产出于海拔5300m的变质地层(黑云母片岩和符山石矽卡岩)之中，根据野外产状可以将其分为两类，一类为强变形锂辉石伟晶岩，其发生明显糜棱岩化作用，呈透镜体形式产出；另一类为弱变形锂辉石伟晶岩，其规模相对较大，变形较弱，但其走向也受区域构造控制。结合地层的变质变形特征，我们认为此处为藏南拆离系的发育位置。成矿伟晶岩下部海拔5200m处出露绿柱石伟晶岩以及切层电气石花岗伟晶岩，5100m处出露电气石白云母花岗岩。通过对电气石白云母花岗岩和两类锂辉石伟晶岩及切层电气石花岗伟晶岩进行独居石和铌铁矿族矿物定年分析，显示电气石白云母花岗岩和锂辉石伟晶岩的形成时代均为25Ma，而切层电气石花岗伟晶岩的形成时代为17.5Ma。岗布锂辉石伟晶岩中铌铁矿族矿物的Mn^# [Mn/(Mn+Fe)]值明显高于切层电气石花岗伟晶岩中的铌铁矿族矿物，同时也高于喜马拉雅带内其他已知伟晶岩的铌铁矿族矿物，反映其岩浆相对富氟的特征。时间上，岗布锂辉石伟晶岩与琼嘉岗(普士拉)和库曲锂辉石伟晶岩基本一致，表明喜马拉雅带内~25Ma是重要的锂成矿期，与藏南拆离系的活动密切相关。空间上，岗布锂辉石伟晶岩的剖面特征与琼嘉岗(普士拉)锂辉石伟晶岩和嘎波锂辉石伟晶岩等类似，均表现为下部为电气石白云母淡色花岗岩，之上为绿柱石伟晶岩，再向上则为锂辉石伟晶岩，成矿伟晶岩的产出明显受藏南拆离系的控制，反映了喜马拉雅带的锂成矿作用具有较好的空间一致性，这对于理解喜马拉雅稀有金属成矿作用与找矿具有重要意义。