Late Eocene–early Miocene provenance evolution of the Crocker Fan in the southern South China Sea

There are many large-scale Cenozoic sedimentary basins with plentiful river deltas, deep-water fans and carbonate platforms in the southern South China Sea. The Crocker Fan was deposited as a typical submarine fan during the late Eocene–early Miocene, and stretches extensively across the entire Sarawak–Sabah of the northern Borneo area. However, systematic analyses are still lacking regarding its sediment composition and potential source suppliers. No consensus has been reached yet on the provenance evolution and sedimentary infilling processes, which seriously impeded the oil-and-gas exploration undertakings. By combining with sedimentary-facies identification, heavy mineral assemblages, elemental geochemistry and detrital zircon U-Pb dating, this paper aims to generalize an integrated analysis on the potential provenance terranes and restore source-to-sink pathways of the Crocker Fan. In general, the Crocker Fan was initially formed over the Cretaceous–lower/middle Eocene Rajang Group by an angular Rajang unconformity. The continual southward subduction of the proto-South China Sea resulted in magmatic activities and subsequent regional deformation and thrusting along the Lupar Line in the northern Borneo. The lowermost Crocker sequence is featured by a thick conglomerate layer sourced from in-situ or adjacent paleo-uplifts. From the late Eocene to the early Miocene, the Crocker Fan was constantly delivered with voluminous detritus from the Malay Peninsula of the western Sundaland. The Zengmu Basin was widely deposited with delta plain and neritic facies sediments, while the Brunei-Sabah Basin, to the farther east, was ubiquitously characterized by turbiditic sequences. The Crocker Fan successions are overall thick layers of modest-grained sandstones, which formed high-quality reservoirs in the southern South China Sea region.     

新疆北天山巴音沟南侧发育早泥盆纪蛇绿岩及其构造意义

北天山晚古生代蛇绿岩带的巴音沟蛇绿岩是该带的重要组成部分和典型代表。传统意义的巴音沟蛇绿岩带在区内分南北两支,南支为贝勒克蛇绿岩带,北支为巴音沟蛇绿岩带,分别代表早泥盆世末和早石炭世末的两条不同古洋壳残片。     

The South East Regional Marine Plan: Implementing Australia's Oceans Policy

In 1998, the Australian Government released Australia's Oceans Policy (AOP), a world first policy initiative focused on providing a framework for integrated ecosystem-based management of Australia's vast marine domain. The South East Regional Marine Plan, the first regional marine plan to be implemented under AOP, was released on 21 May 2004. This paper argues that although full integration across sectors and jurisdictions has not occurred, new AOP initiatives, institutions and governance processes have considerably increased sectoral and jurisdictional coordination in the South East region.     

Zircon U-Pb ages and Hf isotopic characteristics of the Dehe biotite monzonitic gneiss pluton in the North Qinling orogen and their geological significance

The Dehe granitic pluton intruded the Xiahe Group which is in the core complex of the North Qinling Orogenic Belt(NQOB).It shows gneissic bedding and possesses typical S-type granite minerals such as muscovite and garnet.LA-ICP-MS U-Pb isotopic dating of the Dehe granite yielded a weighted average age of 925±23 Ma which represents the emplacement age of the pluton.Most of the εHf(t) values are negative,and the two-stage model ages are consistent with the age of the Qinling Group.The isotope data show that the Dehe granite was formed in the following geological setting:in the syn-collision setting of the NQOB in the Neoproterozoic,crustal thickening induced partial melting of materials derived from the Qinling complex,and then the maga upwelled and intruded into the Xiahe Group.The formation of the Dehe S-type granite implied the occurrence of a convergent event in the QOB during the Neoproterozoic.     

“三江”中段两类碳酸盐岩容矿铅锌矿化成因的相关性——来自稀土元素地球化学研究的启示

世界范围内的碳酸盐岩容矿铅锌矿带内常在区域上出现以方解石等碳酸盐矿物为主要脉石矿物的富碳酸盐型铅锌矿化和以碳酸盐+萤石为主要脉石矿物的富氟型铅锌矿化这两种矿化形式,但不同元素组合的出现在成因上是否有相关性并不明确。青藏高原"三江"成矿带中段玉树地区同一矿集区内近同时发育了东莫扎抓富碳酸盐型和莫海拉亨富氟型铅锌矿床,二者均为碳酸盐岩赋矿,以逆断层为主要控矿构造,具有层控的矿体产状特征,矿石矿物均为方铅矿+闪锌矿,但是,东莫扎抓矿床以方解石+白云石等碳酸盐矿物为主要脉石矿物,莫海拉亨则以方解石+萤石为主要脉石矿物。研究表明,两个矿区含钙矿物的稀土元素地球化学特征存有差异。东莫扎抓矿区方解石的稀土元素具有轻重稀土元素分馏相对明显、轻稀土元素富集、Eu负异常明显的特征,在球粒陨石标准化配分模式图上呈现右倾或轻微右倾的"V"字形曲线。莫海拉亨矿区方解石及萤石轻重稀土元素分馏不明显,有明显的Eu负异常,球粒陨石标准化配分模式图上呈现轻微的"M"型曲线。稀土元素总量上,东莫扎抓(0.46×10-6~10.79×10-6)较莫海拉亨矿床(0.25×10-6~5.88×10-6)高。稀土元素地球化学特征揭示,两个矿床的含钙矿物都沉淀自与岩浆作用无关的热液流体,伴随硫化物沉淀,流体盐度降低,还原性变弱。莫海拉亨矿床除具有一套和东莫扎抓矿床来源一致的流体外,还具有另一套来自深部变质基底的富氟流体,这套流体控制了富氟型碳酸盐岩容矿铅锌矿床的沉淀位置,使其在区域上更靠近逆冲体系主逆冲带,且多在区域上最底层的碳酸盐岩地层中发育。这一认识解释了世界上多个碳酸盐岩容矿铅锌成矿带内同一空间、时间范围内两套不同类型铅锌矿床型式共同出现的原因。     

西藏结则茶卡湖岸沉积物中铀系年龄及意义

通过对藏北高原西北部结则茶卡湖泊及其沿岸地质地貌调查,发现其为一个富含硼、锂、钾、锶的封闭型盐湖,沿岸海拔4 850 m拔湖325 m有一条明显的高位湖岸线,该湖岸线到湖面之间有六级湖积阶地发育,六级以上阶地保存零星。沿湖岸不同高度上的湖积物U系年龄分别为(14.2±1.2)ka BP(T2)、(38.0±3.5)ka BP(T4)和(41.6±3.2)ka BP(T5)。湖面下降的幅度是藏北高原迄今所知最大。根据湖面平均下降速度推算高位湖岸线和高位湖积层的形成年龄在(120~90)ka BP,与东部的纳木错和西部的甜水海基本一致,说明藏北高原在晚更新世初期有一个明显的泛湖期。大约100 ka BP结则茶卡湖面开始下降,晚更新世以来湖泊演化是在封闭体系干旱环境下进行的,盐湖形成于14 ka BP左右,藏北高原在晚更新世以来气候变化可能为自西向东逐渐变为干寒。     

Contested and congested spaces: Exploring authenticity in New Zealand farmers' markets

This paper considers issues of authenticity as they apply to the evolution of farmers' markets in New Zealand. Following a discussion of the nature of authenticity and its deployment by farmers' market organisations in several jurisdictions, a two‐part case study is presented. An analysis of the strategies adopted by Farmers' Markets New Zealand to ‘protect its brand’ nationally and an examination of the disputation of authenticity in the Marlborough Farmers' Market reveals the potential of the ‘authenticity project’ to be a lightning rod for heightened tension and the fracturing of the relationship between competing interests in New Zealand farmers' markets.     

五台杂岩晚太古代花岗质岩石中斜长角闪岩包体的年代学和地球化学研究

华北克拉通中部造山带被认为是由东西部陆块碰撞而产生的陆陆碰撞带,而恒山-五台-阜平地区位于中部造山带的中部,是该地区最大也是最具代表性的基底岩石剖面。总体上,五台杂岩可以分为变质表壳岩和花岗质岩体两大类,前者又被划分为五台群和滹沱群,而后者可划分为2560~2520Ma侵位的强烈变形的闪长岩-英云闪长岩-奥长花岗岩-花岗闪长岩系列、2176~2084Ma侵位的弱变形的斑状正长-钾质花岗岩以及约1810Ma侵位的未变形的A型花岗岩。在晚太古代花岗岩中普遍发育有斜长角闪岩包体,它们在露头上不连续分布,呈绿色到黑色,强烈拉伸成扁条状或透镜状,直径一般在几米到十几米之间。根据地球化学特征恢复它们的原岩为拉斑玄武岩。锆石U-Pb定年结果表明它们的结晶时代为2.7Ga,变质时代为1.85Ga。全岩εNd(t)值为-3.1~+3.5,亏损地幔模式年龄为2.83~3.65Ga。原始地幔均一化蛛网图解上,斜长角闪岩具有明显的Nb、Ta和Ti的负异常,而在球粒陨石均一化稀土元素配分图解中它们具有轻稀土弱富集[(La/Yb)N=1.36~3.52]以及重稀土平坦[(Gd/Yb)N=0.94~1.38]的特征。地球化学以及同位素特征表明它们很可能来自于受到俯冲板片流体改造的轻度富集地幔中尖晶石二辉橄榄岩的部分熔融。更重要地,这些斜长角闪岩包体的锆石U-Pb年龄与全岩Nd亏损地幔模式年龄相似,都为27~28亿年左右,这说明在华北克拉通中部造山带很可能存在过大量的27亿年左右的新生地壳岩石,它们代表了一期重要的地壳生长事件。     

地磁场强度变化对暴露年代测定的影响及校正

在103-105a的尺度上,地磁场强度变化是影响陆地宇生核素生成速率的主要因素,其影响程度取决于样品的地理位置和暴露时间。根据已有的磁场古强度数据,模拟200 ka以来海拔2 km、25°N和40°N的地表10Be生成速率的变化,进而分析地表宇生核素生成速率变化对岩石暴露年代测定的影响及其模式年龄的校正。校正磁场强度变化后,海拔2 km、25°N上,50-200 ka的模式年龄可被压缩14%~19%,大于1σ的误差,相同海拔40°N上的模式年龄可减小约8%。对中低纬两组模式年龄的校正充分证明,磁场强度引起的陆地宇生核素生成速率变化是暴露年代测定中主要误差源之一,尤其在低纬高海拔地区这一影响更不容忽视。     

海平面及海平面变化综述

分析总结了海平面及海平面变化的有关问题,如相关概念及其关系的理解,海平面变化旋回等时性及可对比性,海平面升降曲线的表示方法、内容及绘制技术与原理,其升降幅度的定量化计算和模拟,海平面变化成因的旋回级别、动态分异及成因标识,海平面变化对沉积盆地的影响等等。提出部分建议,包括理清海平面与海平面变化,海平面升降与振荡、波动,全球与相对、高频、复合海平面,ＴＲ旋回与海平面变化等概念;限定其概念的外延、内涵及其之间的关系,以及三、四级海平面变化旋回用于同一大陆或泛大陆的对比性;分清各种表示方法、技术的使用范围,相对水深曲线转换为海平面升降曲线过程中成岩作用、构造沉降、沉积（生产）速率的影响校正及定量模拟;在海平面变化旋回级次格架下结合两种思路进行成因分析;推荐相对海平面升降成因分析按曲线对比法→构造沉降→回剥法思路进行;建议加强海平面升降变化对盆地充填响应的研究;重视对沉积矿床的控制和大陆边缘地壳变形的反弹作用过程及定量模拟。