Origin of natural sulfur-metal chimney in the Tangyin hydrothermal field,Okinawa Trough: constraints from rare earth element and sulfur isotopic compositions

For the first time, we present the rare earth element (REE) and sulfur isotopic composition of hydrothermal precipitates recovered from the Tangyin hydrothermal field (THF), Okinawa Trough at a water depth of 1206 m. The natural sulfur samples exhibit the lowest ΣREE concentrations (ΣREE= 0.65×10^–6–4.580×10^–6) followed by metal sulfides (ΣREE=1.71×10^–6–11.63×10^–6). By contrast, the natural sulfur-sediment samples have maximum ΣREE concentrations (ΣREE=11.54×10^–6–33.06×10^–6), significantly lower than those of the volcanic and sediment samples. Nevertheless, the δEu, δCe, (La/Yb)_N, La/Sm, (Gd/Yb)_N and normalized patterns of the natural sulfur and metal sulfide show the most similarity to the sediment. Most hydrothermal precipitate samples are characterized by enrichments of LREE (LREE/HREE=10.09–24.53) and slightly negative Eu anomalies or no anomaly (δEu=0.48–0.99), which are different from the hydrothermal fluid from sediment-free mid-oceanic ridges and back-arc basins, but identical to the sulfides from the Jade hydrothermal field. The lower temperature and more oxidizing conditions produced by the mixing between seawater and hydrothermal fluids further attenuate the leaching ability of hydrothermal fluid, inducing lower REE concentrations for natural sulfur compared with metal sulfide; meanwhile, the negative Eu anomaly is also weakened or almost absent. The sulfur isotopic compositions of the natural sulfur (δ³⁴S=3.20‰–5.01‰, mean 4.23‰) and metal sulfide samples (δ³⁴S=0.82‰–0.89‰, mean 0.85‰) reveal that the sulfur of the chimney is sourced from magmatic degassing.     

中国中奥陶世岩相古地理

本文是中国早、中、晚寒武世和早奥陶世岩相古地理诸文的继续。在笔者等的华北地区、华南地区和西北地区寒武纪和奥陶纪定量岩相古地理研究及编图成果的基础上,结合其他地区（主要是蒙兴地区、昆仑秦岭地区、西藏地区、海南岛地区和台湾地区）的地质资料,编制出了中国中奥陶世岩相古地理图,并撰写出本文。华北地区、华南地区和西北地区的研究程度较高,其岩相古地理图和文字论述都是定量的。其他地区的研究程度较低,其岩相古地理图和相应的文字论述则是定性的和概略性的。中国中奥陶世岩相古地理的基本格局仍和早奥陶世的一样为“两槽和三台相间分布”。两槽即天山北山蒙辽吉槽地和昆仑秦岭槽地,三台即准噶尔蒙兴台地、塔里木柴达木华北台地和西藏华南台地。但是这些古地理单元及其次级古地理单元的特征却与早奥陶世的有所不同或大不相同。     

Submarine hydrothermal mineralization in the Okinawa Trough, SW of Japan: an overview

The Okinawa Trough is a heavily sedimented, rifted back-arc basin formed in an intracontinental rift zone. Submarine hydrothermal activity is located within the six back-arc rifts located in the middle and southern Okinawa Trough and its distribution is controlled principally by tectonic factors. Subduction of the Daito and Gagua Ridges beneath the Ryukyu Arc has resulted in fracturing of the brittle lithosphere beneath the Okinawa Trough. Hydrothermal activity is strongest in the volcanic arc-rift migration phenomenon (VAMP) area plus the JADE site and Southernmost Part of the Okinawa Trough (SPOT) area which form the prolongation of these two ridges. These areas are characterized by extremely high heat flow locally. Submarine hydrothermal fluids from the Okinawa Trough tend to be strongly influenced by interaction of the hydrothermal fluids with organic matter in the sediment resulting in high alkalinity and NH₄⁺ concentrations of the fluids. The fluids also contain high concentrations of CO₂ of magmatic origin. Submarine hydrothermal mineralization in the trough is diverse. The CLAM site consists principally of carbonate chimneys. Interaction of the hydrothermal fluid with organic matter in the sediment is particularly strong at this site. This is most probably a sediment-hosted deposit in which sulphide minerals have deposited within the sediment column leaving ‘spent ore-fluids’ to emerge at the seafloor. The JADE site consists of active and inactive sulphide–sulphate chimneys and mounds. The Zn–Pb-rich sulphides at this site contain the highest concentrations of Pb, Ag and Au so far recorded in submarine hydrothermal sulphide deposits. At Minami-Ensei Knoll and Hatoma Knoll, active and inactive chimneys consist principally of anhydrite and barite as a result of phase separation of the hydrothermal fluids beneath the seafloor. An intense black smoker has recently been discovered at Yonaguni Knoll in the SPOT area. If it is confirmed that sulphide mineralization is dominant at this site, this could be a highly prospective area. The most prospective areas for economic-grade minerals in the Okinawa Trough appear to be the JADE site and the SPOT area.     

冲绳海槽热流机制浅析

冲绳海槽是一个高热流区，平均热流值极高，但不均匀，实测最小值与最大值相差三个数量级以上，结合海槽地区的构造和地球物理特征，探讨了导致这一高而分散热流特征的多种因素。包括异常壳幔结构。海底热液循环以及地下水对流等，并分析了相应的控制机制。     

The sedimentation rates in the Okinawa Trough during the Late Quaternary

On the basis of accelerator mass spectrometer radiocarbon （AMS ^14C） dating, sedimentation rates of 11 cores collected from the northern to southern Okinawa Trough are discussed. The sedimentation rates in the Okinawa Trough roughly range from 11 to 39cm/ka, and the average is 23.0cm/ka. China＇s continental matter is the main sediment source of the middle Okinawa Trough and has important contribution to the northern and southern Okinawa Trough. The sedimentation rates during the marine oxygen isotope （MIS） 2 are uniformly higher than those during MIS 1 in the northern and middle Okinawa Trough while they are on the contrary in the southern Okinawa Trough. Sedimentation rates in the Okinawa Trough can be one of the proxies of sediment source and an indicator of cooling events.     

0414号"云娜"台风路径分析

通过对0414号“云娜”台风的高空背景场及云图的分析,揭示影响台风移动路径的辛勿理因子。研究结果表明：副高、弱环境场中台风自身内力、台风的非对称结构是影响“云娜”台风移动的主要因素,西风槽对“云娜”台风的移动起着间接作用。     

Surficial Sedimentary Diatoms in Okinawa Trough and Its Response to Kuroshio Current

This paper describes the relative contents of dominant diatom species and the distributive characteristics of tropical pelagic species and diatom assemblages, and also discusses the relations between the relative content of tropical pelagic species and Kuroshio Current and between the distribution of diatom assemblages and material sources. The results show that the limit of＞20% relative content of tropical pelagic species is basically consistent with the demarcation of Kuroshio Current, and that the distributions of dominant diatom species and diatom assemblages reserve the records of their closer relations to material sources.     

环抱式防波堤口门航道横流三维特性研究

环抱式防波堤口门易出现较大横流,且三维特性明显。针对连云港主港区深水航道,建立三维潮流数学模型,并用现场航槽实测资料进行验证,在此基础上计算分析了不同潮差条件下口门段进港航道横流的三维特性。研究结果表明:最大横流约出现在高潮位前1.5 h,自表层至底层相继出现,且表、底层出现时刻仅相差0.5 h;因航道边坡较小,最大横流时未见水流分离现象,航槽底部没有反向流;各层最大横流值均与涨潮潮差有关,且相关程度高;航道内最大横流垂向分布梯度随潮差增加略有增大。     

Different thermal preferences for brooding and larval dispersal of two neighboring shrimps in deep‐sea hydrothermal vent fields

Temperature is an important factor affecting the distributions and life‐history traits of marine animals. Deep‐sea hydrothermal vents are suitable environments to examine ecologic differences related to temperature, due to the steep temperature gradients around the vents. Rearing experiments under various temperature conditions (5–30 °C) at atmospheric pressure demonstrated a difference in thermal effects on egg hatching and larva in two co‐occurring, vent‐associated alvinocaridid shrimps – the peripherally distributed Alvinocaris longirostris and the centrally distributed Shinkaicaris leurokolos. The duration before hatching became shorter as temperature increased, while the maximum hatching rate occurred at higher temperatures in S. leurokolos (10–20 °C) than in A. longirostris (10 °C). Hatched larvae of both species were negatively buoyant, and larva with normal abdominal length could actively swim and stay suspended in the mid‐ or surface water layers of the culture plates under our experimental conditions. However, no larvae settled or metamorphosed into juveniles under the rearing conditions used in this study. Larvae with shortened abdomens occurred under most of the experimental conditions, although they were less frequent at 10 °C in A. longirostris and 20 °C in S. leurokolos. The maximum survival periods at these temperatures were 88 days in A. longirostris and 30 days in S. leurokolos. These characteristics may cause differences in the distributional ranges of the two species. The present results indicate that temperature is an important factor controlling life‐history traits of vent shrimps.     

冲绳海槽浮岩包裹体的测温试验

对浮岩中斜长石斑晶中的包裹体及玻璃基质中的包裹体首先进行双面光薄片的镜下观察，然后进行了系统的均化法与爆裂法测温试验。观察与试验结果表明：(1)斜长石中的包裹体均为玻璃质+气泡的两相包裹体，未发现气—液包裹体。固化包裹体为玻璃质，非晶质的固化包裹体外即是大量的气泡，特别是基质当中气泡更为发育，说明熔浆中含有丰富的挥发性组分，同时也说明包裹体形成于较浅的地质条件下。(2)长石中包裹体的均化温度不受包裹体特征不同的影响，均化温度分布范围从910—1250℃，峰值明显，计算的均化温度为Tz=(1081.4±177.9)℃，但还存在有高于1250℃的均化温度峰。包裹体均化法测试结果说明浮岩中斜长石的形成过程至少有两个阶段：第一阶段的岩浆温度在1200—1300℃左右，在此温度下形成的是An值较高的基性斜长石，同时结晶的还有辉石等矿物，斜长石结晶第二个阶段时的熔浆温度在1100℃以下，这一阶段持续的时间长，跨越的温度范围大，应是岩浆在近地表和岩浆喷出过程中的岩浆快速冷却期，同时伴随有矿物大规模晶出。(3)包裹体中的气相部分均聚合成圆形或近圆形，说明温度下降速度较快。斑晶斜长石中部分包裹体与基质玻璃中包裹体的形成温度是连续变化的，这一事实应该与冲绳海槽特殊的地质条件有关