Elucidating hydrological complexity and climate-influenced diagenesis during the early Carboniferous of South Wales

A revised age provided by conodonts from the Gilwern Oolite of the Clydach area of South Wales allows a clearer understanding of the palaeohydrology, palaeoclimatic history and diagenesis of previously correlated oolitic units. Earlier uncertainty over the apparent sub-regional differences in climate during the early Visean (Chadian—Arundian) lowstand is resolved. Previously a humid interval evidenced by prominent palaeo-epikarst capping the Gilwern Oolite along the northern outcrops of the South Wales synclinorium, was not recognized in what were regarded as correlative outcrops in the Chadian Gully Oolite in the southern part of the synclinorium. Conodont dating now shows that the Gilwern Oolite is much older (Courceyan) than the Chadian Gully Oolite, and during the prolonged exposure of the former there was an interval of weathering under a humid climate. This also explains the contrast between the diagenesis seen between the Gilwern and Gully oolites, which are no longer seen as correlatives.     

The first Surijokocixiidae (Insecta: Hemiptera: Fulgoromorpha) from the Triassic of China

A planthopper originally assigned to the genus Boreocixius in Surijokocixiidae (Surijokocixioidea, Fulgoromorpha) from the Ladinian (Middle Triassic) of Tongchuan in Shaanxi, northwestern China is described as Boreocixius tongchuanensis Zhang et al. sp. nov. As the third species ascribed to the genus, it differs from its congeners in having the much larger tegmen with postnodal veinlets and pigmented bands, providing new morphological information for Boreocixius. The establishment of the new species further increases the diversity of Boreocixius and Surijokocixiidae as well.     

关于《中国扬子区兰多维列统特列奇阶及其与英国的对比》一书若干问题的商榷

《中国扬子区兰多维列统特列奇阶及其与英国的对比》一书（陈旭,戎嘉余,1996）有以下结论：①将回星哨组、茅山组、西坑组等的层位归属于特列奇阶上部;②将回星哨组、茅山组及其相当地层与英国特列奇阶对比;③将扬子区特列奇阶的顶界置于回星哨组、茅山组及其相当地层之顶;④将回星哨组、茅山组、西坑组等地层资料编制的古地理图称为特列奇期晚期古地理图;⑤将回星哨组、茅山组、西坑组等地层与上覆中泥盆统—中二叠统之间的不整合面代表的上升运动,称为“特列奇期的扬子上升”。笔者等依据多年对扬子地台志留纪地层剖面的实地考察和近数十年来扬子区坟头组中—上部、茅山组、回星哨组、小溪峪组、西坑组等地层中文洛克世、拉德洛世、普里多利世早期古生物化石的发现,认为：①回星哨组、小溪峪组、茅山组、西坑组等的层位是文洛克统—普里多利统;② 回星哨组、小溪峪组等大致与英国的文洛克统—普里多利统对比;③回星哨组、小溪峪组、茅山组的顶界是文洛克统—普里多利统剥蚀后残留的层位随地而异的顶界;④根据回星哨组、西坑组、茅山组等地层资料编制的古地理图应是文洛克世—普里多利世古地理图;⑤“扬子地台整个上升”（黄汲清,1945）的时代是志留纪末期,没有“特列奇期的扬子上升”。特提出商榷。上述这些地层时代的解决,对扬子区志留系4统层序的建立具有重要意义,而且也为中国扬子区与英国命名剖面志留系的对比以及中国南方早古生代加里东运动最后一幕时代的再次确定提供了地层学和古生物方面的依据。     

藏南泽当地区大反向逆冲断层变形研究——以磁组构与EBSD组构分析为例

仁布-泽当逆冲断层是喜马拉雅大反向逆冲断层（GCT）在藏南地区的重要延伸部分,也是喜马拉雅造山带北部边界新生代最为活动的构造单元之一。新生代以来特提斯喜马拉雅的构造变形组构特征的研究对于深入理解碰撞造山带演化与高原隆升具有重要构造意义。本文综合GCT泽当-琼结段断层的宏观与微观变形特征,对断裂带石英脉、围岩中石英和云母矿物的电子背散射（EBSD）组构及断层两侧岩石磁组构（AMS）特征进行对比分析。结果表明对AMS主要贡献来自顺磁性云母、绿泥石等,磁化率各向异性椭球体以压扁状为主,磁面理与构造面理（劈理、断层面）基本重合,显示较强的构造变形磁组构特征;磁线理优选方向近南北向,且与观测北向逆冲断层方向一致,揭示剪切作用在变形过程中的持续作用。研究发现泽当地区GCT附近石英微观结构从围岩至断层区,石英至少呈现3种不同类型的微观变形机制：围岩区溶解蠕变、断裂带石英以膨凸重结晶和亚颗粒旋转重结晶作用为主。断裂带石英的c轴EBSD组构指示变形为低温（300~400℃）环境,其中黑云母的结晶学优选（CPO）与磁组构主轴优选方向存在高度的一致性,进一步证实了顺磁性矿物黑云母对AMS的主要贡献。综合研究表明泽当地区GCT的韧性变形是断层处在中上地壳韧性带的活动阶段变形的结果,也代表了特提斯喜马拉雅在碰撞、高原隆升期的变形主要特征。     

安徽滁州和管店早白垩世高镁埃达克质侵入岩的成因:锆石U-Pb年代学和Sr-Nd-Hf同位素的制约

本文以华北陆块东部早白垩世滁州闪长玢岩和管店石英闪长岩为研究对象,报道了新的全岩地球化学（主量元素、微量元素以及Sr-Nd同位素）以及锆石U-Pb年代学和Hf同位素的综合研究结果,进而约束其岩石成因和构造意义。滁州闪长玢岩中锆石发育振荡环带,管店石英闪长岩中锆石具条痕状吸收的特点,它们均为岩浆成因。锆石LA-ICP-MS U-Pb定年结果显示,滁州和管店闪长质锆石年龄分别为128±1Ma和130±2Ma,表明二者均形成于早白垩世。地球化学特征显示,滁州和管店闪长质岩石具有类似的主量元素和微量元素组成,整体具中等的SiO₂含量（58.55%~60.12%）和富MgO（4.43%~5.10%,Mg^#=57~61）的特征,Na₂O/K₂O比值为1.20~1.47,属于高钾钙碱性系列岩石;富集轻稀土元素和大离子亲石元素（如Rb、Ba）,亏损重稀土元素和高场强元素（如Nb、Ta、Zr、Hf）,并具不同程度的Eu负异常（δEu=0.85~0.93）。它们具高的Sr（575×10^-6~1035×10^-6）和低的Y含量（10.2×10^-6~15.3×10^-6）以及高的Sr/Y比值（57~69）,属于埃达克质岩石。此外,滁州和管店闪长质岩石具有类似的Sr-Nd以及锆石Hf同位素的特征,滁州闪长玢岩的⁸⁷Sr/⁸⁶Sr初始比值介于0.7061~0.7066之间,ε_Nd（t）值为-17.7~-16.9,锆石ε_Hf（t）值变化于-23.1~-19.1之间,而管店石英闪长岩的⁸⁷Sr/⁸⁶Sr初始比值为0.7046~0.7059,ε_Nd（t）值为-18.7~-15.8,锆石ε_Hf（t）值为-25.6~-20.0。综合上述,滁州和管店闪长质岩石均属于高镁埃达克质岩石,起源于拆沉的加厚下地壳部分熔融的熔体与地幔橄榄岩反应的产物,形成于早白垩世华北东部陆块拆沉作用下的伸展背景。     

A Comparative Study of the Coal‐forming Characteristics of Marginal Sea Basins and Epicontinental Sea Basins

The coal-forming characteristics,as well as the similarities and differences between epicontinental sea basins and continental marginal sea basins developed during different time periods,were analyzed in this study by adopting comparative analysis thoughts and methods.The results obtained in this study revealed that epicontinental basins and marginal sea basins are both characterized by the main development of thin coal seams or extremely thin coal seams.In addition,changes in sea levels were determined to be the main controlling factors for coal formation,and there were similarities in the continent-sea interactions and coal-forming sedimentary systems of the different basins.However,there were also significant differences observed in the sea level change events,basin basement structural characteristics,coal seam stability levels,accumulation and aggregation characteristics,and the migration patterns of coal-forming materials.For example,the marginal sea basins in the South China Sea were found to be characterized by strong tectonic activities,diversity and complexity.The basin structures showed complex patterns of depressions,uplifts and concave or sag uplifts,which tended to lead to greater complexity in the paleogeographic patterns of the coal formations.This had subsequently resulted in complex coal-forming processes and paleogeographic characteristics,in which the coal-forming zones displayed bead-like distributions,and the enrichment areas and centers were scattered.The practical significance of studying the similarities and differences of the coal-forming characteristics between epicontinental basins and marginal sea basins is that the results can potentially be used to guide the predictions of coal-measure coal seam distributions in South China Sea,as well as provide valuable guidance for future explorations of natural gas reservoirs related to coal measures in the South China Sea area.     

U-Pb Zircon and Re-Os Molybdenite Geochronology of theW-Mo Mineralized Region of South Qinling,China, andtheir Tectonic Implications

A W-Mo mineralized region is located along the northern margin of the South Qinling tectonic belt of China. WMo mineralization occurs mainly in Cambrian–Ordovician clastic and carbonate rocks, and the ore bodies are structurally controlled by NW–SE-and NNE–SSW-striking faults. Evidence for magmatism in the area is widespread and is dominated by intermediate–felsic intrusives or apophyses, such as the Dongjiangkou, Yanzhiba, Lanbandeng, and Sihaiping granitic bodies. Quartz-vein-type mineralization and fault-controlled skarn-type mineralization dominate the ore systems, with additional enrichment in residual deposits. At present, there are few or insufficient studies on(1) the age of mineralization,(2) the relationship between intermediate–felsic granite and W-Mo mineralization,(3) the source of ore-forming materials,and(4) the metallogenic and tectonic setting of the mineralized area. In this paper, we present geochronology results for numerous intrusive granitic bodies in the South Qinling tectonic belt. U-Pb zircon geochronology of the Lanbandeng monzogranite and Wangjiaping biotite monzogranite yields ages of 222.7 ± 2.3 and 201.9 ± 1.8 Ma, respectively. In contrast to the Late Triassic age of the Lanbandeng monzogranite, the age of the newly discovered Wangjiaping biotite monzogranite places it at the Triassic–Jurassic boundary. Re-Os molybdenite geochronology on the Qipangou W-Mo deposit yielded a model age of 199.7 ± 3.9 Ma, indicating the deposit formed in the early Yanshanian period of the Early Jurassic. Granitoid intrusions in the mineralized area are characterized by composite granite bodies that crystallized at ca.240–190 Ma. While there were multiple stages of intrusion, most occurred at 210–220 Ma, with waning magmatic activity at 200–190 Ma. The Re-Os age of molybdenite in the region is ca. 200–190 Ma, which may represent a newly discovered period of W-Mo metallogenesis that occurred during the final stages of magmatism. The heat associated with this magmatism drove ore formation and might have provided additional ore-forming components for metallogenesis(represented by the Wangjiaping biotite monzogranite). Ore materials in the mineralized area were derived from mixed crustal and mantle sources. Enrichment of the region occurred during intracontinental orogenesis in the late Indosinian–Yanshanian, subsequent to the main Indosinian collision. At this time, the tectonic environment was dominated by extension and strike-slip motion.     

The U-Pb Geochronology and Lu-Hf Isotope Compositions of Detrital Zircons from the Nanhua Group of the Longsheng Region, South China and their Implications for Pan-African Events

It is unclear whether the South China blocks have an affinity with continental Gondwana due to a lack of direct Pan-African magmatic and metamorphic features. In this study, we conducted U-Pb geochronological and Lu-Hf isotopic analyses for detrital zircons from a sandstone of the Chang’an Formation of the Nanhua Group in the Longsheng region of northern Guangxi, with the aim of constraining the timing of sedimentation and information as to its source, as well as seeking evidence for Pan-African events in the South China blocks. The results show that the ages of detrital zircons peaked at 654.7 ± 6.2 Ma, 773.2 ± 4.1 Ma and 821.9 ± 6.5 Ma, with some at 920–870 Ma; the youngest age indicates the existence of the Pan-African thermal event. The εHf(t) and TDM2 values demonstrate that the study area has experienced three stages of crustal growth at 3.0–2.4 Ga, 2.1–1.5 Ga and 1.3–0.9 Ga. With intensively distributed Neoproterozoic mafic-ultramafic and granitic plutons emplaced at 830–810 Ma along the southwestern section of the Jiangnan Orogenic Belt and positive εHf(t) values from a large group of zircon grains, it is proposed that the sediments of the Chang’an Formation (of Nanhua Group) were largely sourced from the southeastern margin of the Yangtze block. Comparison with the zircon age spectra of the Cathaysian block shows that about 79% of the Pan-African aged detrital zircon grains that have TDM2 = 1352–1031 Ma and εHf(t) = 3.68–8.79, were sourced from the recycled Grenvillian crust of the Cathaysian block, suggesting that the Cathaysian block had a close connection with Gondwana.     

利用废弃地下空间建设战略原油储备库的构想

当前各国原油储库主要分为地面储库、地下盐穴储库和地下水封洞窟3种类型.根据我国实际情况分析,这3种类型储库均难以在我国推广.通过分析中国东北地区现有废弃矿山情况,结合地下原油储库的工程技术条件,提出了利用废弃矿山改造地下空间,用以建设战略原油储库的构想.建议尽快开展东北地区废弃矿山地下空间综合调查工作,启动相关地下油气储库封闭实验等测试研究工作.     

南秦岭柞山地区铅银锌矿成矿规律及找矿模型

南秦岭柞水银洞子—山阳桐木沟铅银锌矿带地处陕西柞山地区中部,位于中秦岭晚古生代弧前盆地的柞水—山阳矿集区内。该带东西长约71 km,南北宽1～7 km。对带内银洞子（铜）铅银菱铁矿床、黑沟铅锌菱铁矿床、桐木沟锌矿床、南沟（银）铅矿床和松林沟铅矿点的地质、矿体、蚀变、矿化规律进行总结,发现矿体均严格产于中-上泥盆统青石垭组,具有明显的时控、层控、岩控及后期热液改造成矿特征,属典型的海底热水喷流沉积-热液改造层控矿床,构成与晚古生代海底热水喷流沉积-热液改造作用有关的铅锌银成矿系列。建立以层控+热液改造为主控矿条件,以青石垭组热水沉积岩+断裂+化探异常+硫化物、重晶石、菱铁矿蚀变分带为组合的找矿模型,对柞山地区金属矿的找矿突破具有重要的指导意义。