Characteristics of the Geotectonics in South China and Their Constraints on Primary Diamond

The Asian continent is one of the best places in the world to study continental dynamics. In this region the tectonic framework of the South China plate is related to the activity of the Pacific plate and Indian plate since the Mesozoic. In the South China plate, as the ophiolitic melange of the middle Proterozoic in the Shaoxing-Yingtan-Tengxian-Beihai faulted zone was confirmed to be a subducting ocean, the evolution of the Yangtze block and Cathaysian block, which are located on both sides of the fault zone, becomes clearer and clearer. A primary diamond deposit, which was first found by Bao Chaomin and his colleagues in Longyou County of Zhejiang Province in 1998, originated from kimberlitoid pipes. The pipes are located in the Cretaceous basin beside this deep fault and the diamond-bearing pipe was formed deep within a favourable geological structure. Diamond there occurs as octahedral crystals without visual impurities. There are more than 100 similar pipes in the area, which have been poorly stud     

白令海表层沉积物中硅质生物的变化及其环境控制因素

中国首次北极科学考察在白令海采取了12个表层沉积物样品, 其中对硅质生物和陆源碎屑的详细研究发现, 它们主要由硅藻、放射虫和海绵骨针组成.其中, 硅藻在样品中的丰度均占绝对优势, 高出放射虫和海绵骨针一个数量级.它们与环境控制因素关系的分析表明, 硅藻、放射虫和海绵骨针丰度的高低及其保存程度与深度、温度、盐度和受大规模季节性气候变化控制的表层海水的高营养和高生产力, 以及陆源物质输入的变化密切相关.这一研究结果对白令海第四纪的古气候与古海洋学研究具有十分重要的意义.      

Autumn intensification of the Ryukyu Current during 2003-2007

Inverse calculations using data from 16 repeat hydrographic transects collected from April 2003 to June 2007 have yielded velocity structures and volume transports(VTs) of the Ryukyu Current in the region east of the northern Ryukyu Islands.The inverse calculation results show that the Ryukyu Current is dominated by a subsurface velocity core with maximum velocities from 15.1 to 80.0 cm/s,whose positions vary between 110 and 600 dbar and 27.2°-28.2°N along the transect.The mean velocity exhibits a subsurface velocity core with a maximum value of 24.6 cm/s at 326 dbar depth,a VT of 14.0 Sv(1 Sv≡106 m3/s),a vertical dimension of 800 m,and a horizontal dimension of 60 km.The seasonal mean velocities show that the Ryukyu Current is stronger in autumn than in other seasons.It is suggested that this seasonal variation is coincident with the intensification of the anticyclonic eddy south of Shikoku,Japan.     

The distribution feature of size-fractionated chlorophyll a and primary productivity in Prydz Bay and its north sea area during the austral summer

The investigation of size-fractionated chlorophyll a and primary productivity were carried out in three longitudinal sections (63°-69°12'S, 70°30'E, 73°E and 75(30'E) at December 18-26, 1998 and January 12-18, 1999 in Prydz Bay and its north sea area, Antarctica. The results showed that surface chlorophyll a concentration were 0. 16 -3. 99 μg dm-3. The high values of chlorophyll a concentration (more than 3.5 μg dm -3) were in Prydz Bay and in the west Ladies Bank. The average chlorophyll a concentration at sub-surface layer was higher than that at surface layer; its concentration at the deeper layers of 50 m decreased with increasing depth and that at 200 m depth was only 0. 01 -0. 95μg dm -3. The results of size-fractionated chlorophyll a showed that the contribution of the netplanktion to total chlorophyll a was 56% , those of the nanoplankton and the picoplankton were 24% and 20% respectively in the surveyed area. The potential primary productivity at the euphotic zone in the surveyed area wa     

Tectonic and Hydrocarbon Accumulation Elements Characteristics of the Tethyan Realm in South China

Abstract: The evolution of the global Tethys Sea can be classified into three stages, Proto-Tethys, Paleo-Tethys and Neo-Tethys. The Tethyan realm has distinctive features of zonations and segmentations along north-south and east-west, respectively, and has variable richness in oil and gas. The petroleum geological conditions of Tethys are complicated, partly represented by multi-layer of source and seal rocks, and reservoirs. The hydrocarbon accumulation elements and periods of the Tethyan realm show gradually younger from west to east and north to south. South China is located in the north belt and Yangtze segment of the Tethyan realm, and its polycyclic tectonic movements were governed by the Tethyan and Pacific realms. The blocks in South China rotated clockwise and counter-clockwise during their drift northward from Gondwana. The belts and segmentations of Tethys in South China are also clear, with six tectonic belts including: Chuxiong-Sichuan; middle Guizhou-Hunan-Hubei; lower Yangtze; Xuefeng-Jiangnan; Guangxi-Hunan-Jiangxi; and Cathaysia. Numerous faults, including compressional, compressional-shear, extensional, extensional-shear and shear are well developed in South China. The fault strikes are mainly NE, NW and NS, in which the NE is the dominant direction. Lower, middle and upper hydrocarbon assemblages, respectively corresponding to Proto-, Paleo- and Neo-Tethys, formed in the Tethyan realm of South China with the lower and middle having excellent hydrocarbon accumulation conditions. An integrated analysis of tectonic evolution, superimposed deformation and later hydrocarbon preservation shows that during the Neo-Tethyan stage in South China, continental sediments were deposited and experienced intense tectonic deformation, which had resulted in different hydrocarbon pool-forming features from those of the Neo-Tethyan realm.     

Expansion of the Cathaysian Oldland through the Ordovician-Silurian transition:Emerging evidence and possible dynamics

Located northwest of the Jiangshan-Shaoxing Fault Zone,western and northwestern Zhejiang and northeastern Jiangxi provinces experienced major changes in bio-and litho-facies and paleogeography through the Ordovician-Silurian transition (late Katian,Hirnantian,and early Rhuddanian),as manifested by stratigraphic,paleontologic and synecologic records.Three geographic units under consideration are South,Central,and North areas.The western margin of the South area was occupied by the Huaiyu Mountains,whereas th...     

西湖硅藻对桡足类浮游动物繁殖的影响

本文报道从杭州西湖筛选分离的两种淡水硅藻,即尖针杆藻Ｓｙｎｅｄｒａａｃｕｓ和谷皮菱形藻Ｎｉｔｚｓｃｈｉａｐａｌｅａ对西湖两种淡水浮游桡足类,即近亲拟剑水蚤Ｐａｒａｃｙｃｌｏｐｓａｆｆｉｎｉｓ和大尾真剑水蚤Ｅｕｃｙｃｌｏｐｓｍｕｃｒｒｏｉｄｅｓ卵孵化率的影响。结果表明,在较高密度的硅藻培养液（１．２×１０４～５．４×１０４个／ｃｍ３）中培养的桡足类动物,其卵的孵化率比生活在自然水体中的有明显降低,并发现该密度的实验硅藻对其摄食者——桡足类的母体也产生一定的毒害作用。该实验结果与已报道的某些海洋硅藻对海洋桡足类存在毒害作用的结果,对水域生态系食物链（网）中硅藻作用的传统概念提出了挑战,对水域生态学研究提出了新课题。     

Chaos Dynamic Behaviour of Mineralization

In this paper a nonlinear dynamic model for the distribution of element content and mineralization in the crust is suggested and the iteration relationship formula of this model coincides with the logistic equation. This shows that mineralization related with migration and enrichment of elements is in chaos, thus resulting in fractal structures of element content and ore reserves and their spatial distribution in the crust.     

Reliability-Based Load and Resistance Factors Design for Offshore Jacket Platforms in the Bohai Bay： Calibration on Target Reliability Index

The target reliability index has been effectively used as the best solution to deal with the relationship between the structural safety and the optimal economy in any structural design.However,the target reliability index for offshore jacket platforms based on different sea areas in China has never been calibrated.This paper presents an approach for its calibration,and suggests many kinds of associated load cases.The uncertainties of loads and structural resistance are mainly investigated.The target reliability index for structural components,tubular joints and piles of offshore jacket platforms are discussed respectively in detail.Finally,through the calibrated results from the offshore jacket platforms of QK18-1,JZ20-2,SZ36-1 and BZ28-1 in the Bohai Bay,it is proposed to adopt 2.8 as the target reliability index of offshore jacket platforms in the Bohai Bay for a 25-year design period.The results provide significant reference for the design of offshore jacket platforms.