琼东南盆地井震地层对比分析及区域地层格架的建立

琼东南盆地历经断陷、断坳、裂后热沉降和裂后加速沉降等一系列的构造变动,沉积环境由始新世的滨海环境发展为现今的深水环境,形成了一套包括滨岸沉积、滨浅海沉积、陆架和陆坡沉积、以及半深海沉积的地层组合,具有良好的油气资源的生储盖条件,已成为当前油气资源勘探开发的重点区域。本文首先对盆地区域内钻井和地震剖面进行了主要地层界面(T20、T30、T40、T50、T60和T70)的识别和提取(点),继而结合连井地震剖面(线)和盆地区域过井地震剖面(面)对主要地层界面做了追踪对比分析,再依据古生物年代,建立了适用于琼东南盆地的区域地层年代格架。在琼东南盆地浅水区主要沉积了新近系地层(T60-T20),断裂基本不发育,地层厚度变化不大,极少有明显的上超和削截,局部地区发育有利于油气储集的三角洲沉积体系,表明琼东南盆地新近纪时期受构造作用影响较小。在深水区,新近系地层(T60-T20)和浅水区特征相似,仅反射特征有所不同;古近系地层(T100-T60)内部层序结构主要为楔状或近平行状,具有明显的上超和削截,地层厚度较大,断裂明显并导致地层错断,表明琼东南盆地深水区在古近纪时期主要受构造作用控制,并伴随着强烈的拉张和快速沉降作用,沉积环境主要为浅海。在近东西向的中央峡谷内存在有三期砂体:第一期砂体(井深3 528~3 336m,厚约192m)形成于距今11.6~5.5Ma(T40-T30),分布范围跨越中央峡谷的陵水-松南-宝岛段,沉积物构成包括浊积水道沉积、浊积席状砂、块体流沉积、深海泥质沉积、天然堤及漫溢沉积等;第二期砂体(井深4 100~3 900m,厚约200m)形成于距今5.5~4.2Ma(T30-T29),分布范围跨越中央峡谷的乐东-陵水段,以重力流沉积为主;第三期砂体(深度3 630~3 400m,厚约230m)发育于距今4.2~3.6Ma(T29-T28),分布于峡谷的乐东-莺东段,以浊积水道沉积为主。三期砂体在琼东南盆地中央坳陷带自东向西、由老到新依次展布,构成了良好的油气储层体。     

Estimating time-based instantaneous total mortality rate based on the age-structured abundance index

The instantaneous total mortality rate(Z) of a fish population is one of the important parameters in fisheries stock assessment. The estimation of Z is crucial to fish population dynamics analysis,abundance and catch forecast,and fisheries management. A catch curve-based method for estimating time-based Z and its change trend from catch per unit effort(CPUE) data of multiple cohorts is developed. Unlike the traditional catch-curve method,the method developed here does not need the assumption of constant Z throughout the time,but the Z values in n continuous years are assumed constant,and then the Z values in different n continuous years are estimated using the age-based CPUE data within these years. The results of the simulation analyses show that the trends of the estimated time-based Z are consistent with the trends of the true Z,and the estimated rates of change from this approach are close to the true change rates(the relative differences between the change rates of the estimated Z and the true Z are smaller than 10%). Variations of both Z and recruitment can affect the estimates of Z value and the trend of Z. The most appropriate value of n can be different given the effects of different factors. Therefore,the appropriate value of n for different fisheries should be determined through a simulation analysis as we demonstrated in this study. Further analyses suggested that selectivity and age estimation are also two factors that can affect the estimated Z values if there is error in either of them,but the estimated change rates of Z are still close to the true change rates. We also applied this approach to the Atlantic cod(G adus morhua) fishery of eastern Newfoundland and Labrador from 1983 to 1997,and obtained reasonable estimates of time-based Z.     

Paleomagnetism of the middle Cretaceous Iritono granite in the Abukuma region, northeast Japan

We have studied the paleomagnetism of the middle Cretaceous Iritono granite of the Abukuma massif in northeast Japan together with ⁴⁰Ar–³⁹Ar dating. Paleomagnetic samples were collected from ten sites of the Iritono granite (102 Ma ⁴⁰Ar–³⁹Ar age) and two sites of its associated gabbroic dikes. The samples were carefully subjected to alternating field and thermal demagnetizations and to rock magnetic analyses. Most of natural remanent magnetizations show mixtures of two components: (1) H component, high coercivity (B_c > 50–90 mT) or high blocking temperature (T_b > 350–560 °C) component and (2) L component, relatively low B_c or low T_b component. H component was obtained from all the 12 sites to give a mean direction of shallow inclination and northwesterly declination (I = 29.9°, D = 311.0°, α₉₅ = 2.7°, N = 12). This direction is different from the geocentric axial dipole field at the present latitude (I = 56.5°) and the typical direction of the Cenozoic remagnetization in northeast Japan. Since rock magnetic properties indicate that the H component of the Iritono granite is carried mainly by magnetite inclusions in plagioclase, this component probably retains a primary one. Thus the shallow inclination indicates that the Abukuma massif was located at a low latitude (16.1 ± 1.6°N) about 100 Ma and then drifted northward by about 20° in latitude. The northwesterly deflection is attributed mostly to the counterclockwise rotation of northeast Japan due to Miocene opening of the Japan Sea. According to this model, the low-pressure and high-temperature (low-P/high-T) metamorphism of the Abukuma massif, which has been well known as a typical location, would have not occurred in the present location. On the other hand, the L component is carried mainly by pyrrhotite and its mean direction shows a moderate inclination and a northwesterly declination (I = 42.8°, D = 311.5°, α₉₅ = 3.3°, N = 9). Since this direction is intermediate between the H component and early Cenozoic remagnetization in northeast Japan, some thermal event would have occurred at lower temperature than pyrrhotite Curie point ( 320 °C) during the middle Cretaceous to early Cenozoic time to have resulted in partial remagnetization.     

基于粗糙度的月表虹湾地区地形地貌解译

行星表面粗糙度是表面侵蚀、沉降和隆升等作用在行星表面留下的记录,对其进行的定量分析可以精确地反映其表面地质构造过程.对月球的虹湾地区选取水平方向的12条剖面进行了粗糙度各参数(均方根高程、均方根偏差、均方根坡度、Hurst指数)的计算,结果表明:①在1 km的剖面长度上,虹湾地区均方根高程的平均值在3 m左右;在0.2...     

Index to Volume 99

Abstract

Capitals of the World, Version 1.5, by Keith Sutton, P.O. Box 23668, San Diego, CA 92123, Registered Copy $20. FPCL disk #2292 (Version 1.3).

Terra?Time, version 5.0, by George K. Marek, GeoGraphic Software, 126 Mountain View Road, Glastonberg, CT 06033, Registered Copy $20. FPCL Disk #1487.

World City Distance Computer, version 5.0, by George K. Marek, GeoGraphic Software, 126 Mountain View Road, Glastonberg, CT 06033, Registered Copy $15. FPCL Disk #1487.

The Transfer and Transformation of Ideas and Material Culture. by Hugill, Peter J. and Dickson, D. Bruce, eds.: College Station, Texas: Texas A&;M University Press, 1988. xxii and 281 pp., index.

The Third World: States of Mind and Being edited by J. Norwine and A. Gonzalez Winchester, MA: Unwin Hyman, Inc. 1988. Refs., notes, index. 275 pp. ISBN 0–04–910121–8.

The Carrier Wave: New Information Technology and the Geography of Innovation 1846–2003 by Peter Hall and Paschal Preston Winchester, MA: Unwin Hyman Ltd. 1988. Tables, figs., refs., index. 305 pp. $34.95, cloth.     

Life Geography from the Child's Point of View

Abstract

A second look is taken at “The Geography of the U.S. in the Year 2,000.” A new interplay is seen of the countervailing pressures to disperse and to agglomerate. Polynucleated urban regions are seen, organized within and around a global poly center. There are certain imperatives: those of demographic cycles and of the economic long wave. These will interact with information-age technologies to change family structures, life styles, and locational preferences. The unexpected also should be expected: “catastrophes” in which existing arrangements are transformed and new structures put into place to replace them. A key to understanding is to continually probe the second derivatives: change in the nature of change.     

中甸矿集区普朗-红山铜多金属成矿亚带北段帕纳牛场斑岩体~(40)Ar—~(39)Ar年龄及锑矿化

普朗-红山铜多金属成矿亚带北部帕纳牛场辉锑矿床与石英二长斑岩(热液)及断裂有关。斑岩黑云母40Ar-39Ar坪年龄和等时线年龄分别为199.1±1.3Ma和199.2±2.4Ma,代表了与辉锑矿化对应的斑岩的侵位时间,是该成矿亚带上目前获得石英二长斑岩中40Ar-39Ar最年轻的新年龄值,代表了义敦岛弧普朗-红山铜多金属成矿亚带存在燕山早期的构造-岩浆活动。在印支晚期主要形成斑岩型-夕卡岩型铜多金属矿床之外,燕山早期还具有斑岩及至少与斑岩有关的热液脉状成矿作用-锑矿化,预示了本区斑岩的一种新的成矿作用和找矿方向与前景。     

西昆仑库地蛇绿岩中基性火山岩的Sm-Nd等时线年龄

本文总结了前人有关库地蛇绿岩系各组成单元以及与其有成因联系的岩浆岩的年代学资料,同时利用Sm-Nd法测定了一些克沟基性火山岩的形成时代,获得了 2个晚元古代全岩等时线年龄:1023±51 Ma和834±29 Ma。在此基础上,对库地蛇绿岩系的形成和演化时代进行了讨论,认为库地蛇绿岩中基性火山岩的Sm-Nd等时线年龄可能代表了库地洋开始消减俯冲的年代。     

东天山卡拉塔格早古生代红海块状硫化物矿床精确定年及其地质意义

东天山卡拉塔格矿带红海块状硫化物Cu-Zn矿床产于卡拉塔格海相火山岩建造中,矿层主要与两个岩性段的火山-碎屑岩地层有关:(1)盖层为中性-酸性火山岩、火山角砾岩、凝灰岩,夹凝灰质砂岩;(2)赋矿层位主要由中基性-中酸性火山角砾岩、凝灰角砾岩、凝灰岩和沉凝灰岩组成。高精度的锆石离子探针U-Pb同位素定年获得矿体上盘围岩底部酸性火山岩的年龄为416.3±5.9Ma,为成矿时代的上限年龄;K-Ar同位素定年获得矿体下盘强绢云母化蚀变围岩年龄为424±7Ma,记录了最晚一期成矿热液活动的时代。同位素年代学研究显示,卡拉塔格地区在早古生代末期存在一期铜多金属成矿作用,这个认识不仅为吐哈盆地南缘古生代火山岩地层的时代划分提供了年代学限制,而且扩大了卡拉塔格地区和区域找矿空间。     

Zircon U-Pb age,geochemical and Nd isotopic data of Middle Jurassic high-Mg dioritic dike in Liaodong Peninsula,NE China

Zircon LA-ICP-MS U-Pb age, geochemical and Nd isotopic data are presented for a newly recognized high-Mg dioritic dike from Haicheng, Liaodong Peninsula, NE China, to constrain its petrogenesis. The zircons from the high-Mg diorite exhibit striped absorption and oscillatory growth zoning in the cathodoluminescence （CL） images, and have high Th/U ratios （0. 05-0.9）, indicating a magma origin. Zircon LA-ICP-MS U-Pb dating indicates that 206pb/238U ages of 12 spots of zircons are between 167 Ma and 178 Ma, yielding a weighted mean 206pb/238U age of 172 ＋ 2 Ma （MSWD =4. 1 ）, which represents the forming age of the high-Mg dioritic dike, i. e. Middle Jurassic. Geochemically, the samples have SiO2 =55.4-60. 6 wt. % , Na20 =2. 2-2.76 wt. % , K20 = 1.32-2. 02 wt. % and （Na2O ＋ K2O） =3.82--4. 47 wt. %, belonging to sub-alkaline series and displaying a calc-alkaline evolutionary trend. They are characterized by high MgO （4. 75-6.85 wt. % ）, Mg# （55-61）, Cr（130-262 ppm）, Ni（63-130 ppm）, Sr（568-857 ppm）, and Ba（484-1 130 ppm） contents, with geochemical features analogous to those of high-Mg adakites. They show variable end （t） values （ - 1.3 to - 3.9） , with a weighted value of - 2. 7, which plot intermediately between the field of the ancient continental crust and the depleted mantle source, indicating that both the lower crust and mantle source are necessary for the generation of the parent magma of the Haicheng high-Mg diorites. The Haicheng high-Mg dioritic dike in the Liaodong Peninsula and the Jurassic magmatism in the eastern North China Craton formed under a continental crustal thickening setting that may be related to subduction of the Paleo-Pacific oceanic plate.