苏北云台群含蓝晶石岩石矿物组合特征及其地质意义

中上元古界云台群中的石英岩类、某些片岩类是含蓝晶石的层位。与蓝晶石共生的黄玉、天蓝石、磷钙铝石、叶腊石、金红石等矿物构成高压变质带里原岩为泥质、泥砂质的白片岩或类白片岩的一套矿物组合。它们将成为今后岩石学研究的新领域,同时也是今后寻找金刚石、刚玉、磷、镁等矿产的线索之一。     

DYNAMIC AND THERMOHALINE PROPERTIES OF THE MINDANAO UNDERCURRENT,PART Ⅱ: THERMOHALINE STRUCTURE

INTRODUCTI()NThenorthwardflowingMUCbelowtheMCwasfotmdandnamedbyHuandCui(1989,l99l)usinghydrographicdataofOctoberofl987and1988gatheredddringtheChineseAcademyofSCiencesmtilti-institutionalpro~onAirSeaInteractionintheWesternTropicalPacificandIntemalCliInaeChange(CAS)-Recently,WangandHu(l997,hereinafer,wn)eednedtheMUCdrodricstmctUreusinghydrOgraPhicdataof1lcmisesconductedatnear8"NzonalsectionsbytheCASprograrnandthePRC-USJointProgramonAir-SeaInteractionintheWestemEqUatorialP…     

Dynamic and thermohaline properties of the Mindanao Undercurrent, part II: Thermohaline structure

Hydrographic data from eleven 1986–1991 cruises at zonal sections near 8°N from the Philippine coast to 130°E were used to examine thermohaline structures and water mass properties of the western boundary currents there, especially those of the Mindanao Undercurrent (MUC). The finding that the MUC consisted of two water masses with salinity of 34.6 at 26.9 σ_t and 34.52 at 27.2 σ_t which were remnants of the lower part of the Southern Pacific Subtropical Water (SPSW) and of the Antarctic Intermediate Water (AAIW) of South Pacific origin, respectively, showed that the MUC was not a local transient but originated elsewhere. As the MUC flowed from 7.5°N to 8°N, part of it carrying the SPSW turns anticyclonically and eastward. The Northern Pacific Intermediate Water (NPIW) often joins the MUC, which suggests that the NPIW carried by the MC partly returns northward as a result of the shear between the MC and the MUC or other processes. The shear instability provides the energy for the irregular fluctuation of the MUC. Contribution No. 3256 from the Institute of Oceanology, Chinese Academy of Sciences. Project 49176255 and 49706066 supported by NSFC, and also by Foundation of Post-doctoral Research.     

华北地块北缘金、多金属成矿地质背景

华北地块北缘是我国重要的金、多金属成矿带。根据区域地质建造特点、构造性质将研究区划分为５种成矿地质背景。不同的区域成矿地质背景有不同的成矿特点：变质基底区,主要形成沉积变质改造型ＣｕＦｅＡｕＰｂＺｎ成矿系列;盖层区,主要在中晚元古代沉降区形成ＰｂＺｎ（Ａｇ）沉积成矿系列、ＰｂＺｎ（ＡｇＡｕ）沉积改造成矿系列;地槽区,主要形成中酸性岩浆热液多金属成矿系列,火山－次火山热液金、多金属成矿系列,基性－超基性岩浆ＣｕＮｉ成矿系列;中生代火山断陷盆地,主要形成中酸性火山－次火山金、多金属成矿系列;构造岩浆活动带则广泛形成中酸性岩浆热液金、多金属成矿系列。     

Seasonal and long-term sea-level variations and their forcing factors in the northern Bay of Bengal: A statistical analysis of temperature,salinity, wind stress curl,and regional climate index data

In the northern Bay of Bengal, mechanisms of seasonal sea-level variation have not previously been examined, and the understanding of longer-term inter-annual sea-level variation is also not concrete. These parameters are addressed in this study utilizing available tide gauge and satellite altimetry data. The contribution of steric sea level to seasonal and longer-term inter-annual sea-level variations is quantified, and statistical analysis is performed to determine the correlations of various atmospheric and oceanic factors with sea level. This study suggests that the trend of sea-level rise in this bay (4 ± 1.33 mm/year) is higher than the global average (3.32 ± 0.46 mm/year) for the studied period 1993 to 2018. The rate of sea-level rise is higher along the coast than in the offshore area and the highest in the central part of the coast. Sea level shows a strong seasonal variation: sea level is the lowest in the winter but the highest in autumn. The contribution from the thermosteric sea level is higher to the observed sea level from winter to early summer, whereas contributions from the halosteric sea level and wind stress curl are higher during autumn. Long-term variations in sea level show strong positive correlations with thermosteric sea level, indicating that temperature is a major local controlling factor for sea-level change. In addition to local factors, long-term sea level also varies by remote forcing (equatorial zonal wind stress), which explains approximately 36 % of the sea-level variation in this bay. Sea level is low during the combined events of positive Indian Ocean dipole (IOD) and El Niño, whereas the sea level is high during the combined events of negative IOD and La Niña. This study provides an improved understanding of seasonal and longer-term inter-annual variations of sea level and the necessary groundworks for a dedicated model study to further quantify all the components of the sea-level budget in the study areas.     

我国沙漠化研究的若干问题--4.沙漠化的防治战略与途径

沙漠化是干旱、半干旱及部分半湿润地区由于人地关系不相协调所造成的以风沙活动为主要标志的土地退化。目前我国沙漠化防治仍然面临着“局部治理,整体恶化”的严峻态势。为了使沙漠化防治更加有效,需要我们以自然与人为因素及其相互作用为主线,对沙漠化的成因、发展或逆转过程、沙漠化土地时空分布特征及其变化等关键问题有进一步的认识,进而明确沙漠化防治的战略和途径。根据我们的研究和总结,提出了我国沙漠化防治的战略、指导方针、基本原则和途径。     

Invasion of anthropogenic CO<Subscript>2</Subscript> recorded in planktonic foraminifera from the northern Gulf of Aqaba

The stable carbon isotopic composition of the planktonic foraminifera Globigerinoides sacculifer and G. ruber (white) and sedimentary organic matter from the northern Gulf of Aqaba have been investigated to estimate changes in ¹³C_DIC in surface waters during the last 1,000 years. The high sedimentation rates at the core sites (about 54 cm/Kyear) provide high temporal resolution (~10 years). Recent sediments at the top of the cores reflect conditions younger than 1950. The ¹³C records of the planktonic foraminifera from three multicores display similar trends, showing a uniform and consistent pattern before the 1750s, and a gradual decrease of approximately 0.63 over the last two centuries. This decrease seems to track the decrease of ¹³C_DIC in surface waters, which is mainly caused by the increase of anthropogenic input of ¹³C-depleted CO₂ into the atmosphere. Similarly, a trend towards lighter values of the carbon isotopic composition of sedimentary organic matter (¹³C_org) during the last 200 years supports the interpretation obtained from the planktonic foraminiferal ¹³C. Furthermore, direct measurements of seawater show that ¹³C of the dissolved inorganic carbon (DIC) in the northern Gulf of Aqaba has decreased by about 0.44 during the period 1979–2000. The average annual decrease is 0.021, which is similar to that observed globally. The ¹³C values of planktonic foraminifera combined with organic matter ¹³C from marine sediments are good indicators for reconstructing past changes in atmospheric CO₂ concentrations from the northern Gulf of Aqaba.     

Molluscan Hard-Substrate Associations in the Northern Red Sea

Abstract. The mollusc associations of 29 hard-substrate localities in the Northern Bay of Safaga Red Sea, Egypt were studied. The hard substrates were classified into 7 types: reef flats, intertidal rock bottom, very shallow subtidal conglomerate, Porites carpet, faviid carpet, platy scleractinian association, Sarcophyton carpet. Based on a cluster analysis the molluscs of these hard substrates can be classified into 5 groups: Group A is dominated by Dendropoma maxima , Chamoidea and Tridacna maxima , group B by Pedum spondyloideum, T. maxima and Coralliophila neritoidea , group C by Chamoidea and Cerithium rüppelli , group D by Modiolus auriculatus , Chamoidea, Morula granulata and Nerita albicilla and group E by Chamoidea and Pitar hebraea . The latter group contains only samples which are generally poor in molluscs. Group A molluscs are diagnostic for reef flats, group B for Porites and faviid carpets, group C for Sarcophyton carpets and group D for tidal/shallow subtidal rock substrates. The different hard substrates are therefore characterized by diagnostic mollusc associations and some of them could also be identified in the fossil record.     

南海中北部热带气旋强度突变的天气气候特征分析

本文对1960-2002年在南海中北部活动的热带气旋进行分析统计,发现有如下气候特征：南海中北部平均每年有6.7个热带气旋,有4.9个热带气旋强度发生突变,其中有3%的热带气旋只发生突然增强,72%的热带气旋只发生突然减弱,25%的热带气旋既发生突然增强又发生突然减弱过程.强度突然减弱发生在4-12月,主要集中在登陆和登陆后的陆地区域,分布较广;强度突然增强发生在4-11月,主要出现在珠江口以西至海南岛东部海面、东沙群岛和西沙群岛海面.     

Buoy measured wind, wind stress and wind stress curl over the shelf off Bodega Bay, California

An array of five buoys and three coastal stations is used to characterize the winds, stress, and curl of the wind stress over the shelf off Bodega Bay, California. The wind and wind stress are strong and persistent in the summer and weak in the winter. In the summer, wind and stress decrease strongly across the shelf, toward the coast. Combinations of buoys are used to compute the curl of the wind stress over different portions of the shelf. The mean summer 2001 curl of the wind stress over the array depends upon the area selected, varying between −1.32×10⁻⁶ and +7.80×10⁻⁶ Pa m⁻¹. The winter 2002 wind-stress curl also depends on location, varying from −2.06×10⁻⁶ to +2.78×10⁻⁶ Pa m⁻¹. Mean monthly curl of the wind stress is a maximum in the summer and a minimum near zero in the winter. In both the summer and the winter, the correlation between the wind-stress curl for different portions of the shelf varies between moderate negative, though insignificance, to high positive. A wind measurement at a single point can be poorly related to the measured curl of the wind stress at other locations over the shelf. The measurements show that the use of one wind measurement to characterize the curl of the wind stress over the shelf without further investigation of the local wind-stress curl structure is risky.