Cenozoic paleomagnetic results and phanerozoic apparent polar wandering path of Tarim Block*

New paleornagnetic data from Cenozoic rocks in Tarim enable people to revise the Phanerozoic apparent polar wandering path (APWP) of this block. This modified Tarim APWA is supported by data from other Chinese blocks. On the basis of the APWA, it is concluded that Tarim rode on a plate subducting under the Kazakhstan plate between Carboniferous and Permian time. By the Late Permian, subduction had finished. The APWP also revealed that tectonic evolution of the Tarim was characterized by northern latitudinal displacement during the Paleozoic time, while Tarim remained at relative low latitude (about 20°) until1 Cretaceous.     

A preliminary research establishing the present-time intraplate blocks movement model on the Chinese mainland based on GPS data

The Chinese mainland is regarded as the best area for studying the continental crustal movement and dynamics. In the past, based on the ground surface observation, it was very difficult to study the movement of the intraplate blocks within a range of larger space and a time scale of several years quantitatively. In this paper, a method of calculating the Euler vectors of present-time motion among blocks by using Cardan angles has been given completely based on two periods of GPS repetition measurement data of the National Ascending Plan of China (NAPC) — the study and application of current crustal movement and geodynamics in 1994 and 1996. A present-time blocks movement model on the Chinese mainland (PBMC-1), which describes the motion of seven blocks—Tibet, Chuan-Dian, Gan-Qing, Xinjiang, South China, North China and Heilongjiang block, is established preliminarily. The velocity field of the relative motion among the intraplate blocks and boundary motion in the Chinese mainland are firstly given within several years time scale. It is shown by the results calculated with the model that the velocity-rate of each block is reduced gradually from the south to north and from the west to east, and the motion direction changes gradually from NNE to E, even SEE or SE. The collision of Indian plate plays a leading role in the movement of the intraplate blocks in the Chinese mainland, while the motion manner and velocity-rate of block boundary zone (fracture zone) depend on the motion of every block again. The present-time motion of a time scale of several years computed with the model is not only largely consistent with the average motion of a time scale of several million years derived from geology, but also very coincident with the results of geophysical and astronomic observation. It is shown preliminarily that the observed results of space geodesy techniques such as GPS etc. are capable of discovering the crustal movement at present. This study is supported by the National Natural Science Foundation of China (NNSFC), National Ascending Plan of China (NAPC) and Chinese Joint Seismological Science Foundation (CJSSF).     

青藏高原东北隅似三联点构造特征

在大陆内部,对于一定尺度的构造块体,似三联点构造是一种普通的构造形式。由于大陆内部块体旋转的普遍性,似三联点构造可形成顺旋型和逆旋型两种构造型式。     

New paleomagnetic results from Ceno-Mesozoic volcanic rocks along southern rim of the Tarim Basin,China*

Paleomagnetic samples were collected from four localities located in the southern rim of the Tarim basin. The samples were taken from volcanic rocks erupted between Jurassic and Quaternary. Detailed analysis of all samples has been carried out with progressive thermal demagnetization. A characteristic remanence (ChRM) with higher unblocking temperature has been isolated from all samples. The pole position from the middle Jurassic is at 52.5°N, 187.9°E(dp = 3.7°,dm =6.5°); the directions of the ChRM of Cretaceous correspond to a paleopole at 69.7°N, 211.6°E (dp = 9.8°,dm = 15.9°); the Quaternary pole from the Pulu site is at 79. 9°N, 183.1°E(dp = 1.6°.dm =2.4°). On the basis of these new paleomagnetic data, tectonic evolution of Tarim block is presented.

     

胶东望儿山金矿带有限应变分析及其意义

望儿山金矿带中广泛发育变形石英颗粒。经三维有限应变分析表明,望儿山断裂曾经历过强烈的挤压作用,金矿体定位于断裂带的扩容空间,矿体附近付林参数普遍表现为拉伸型。构造岩有限应变椭球体拉伸轴,主要集中于ＮＥ—ＳＷ向,含矿热液在区域应力及岩浆热动力作用下,沿望儿山断裂带运移。成矿过程中,体系是开放的。     

岩浆岩型伴生金矿床的时空分布特征及区域控矿作用

从伴生金的角度对岩浆岩型矿床的时空分布特征及区域控矿作用进行了总结：划分了吉中、北阴山、富蕴、金川、玛沁、略阳、康滇、哀牢山八个成矿带;指出岩浆岩型伴生金矿床最主要的成矿期为元古代和晚古生代;强调台褶过渡区及褶皱过渡区、深大断裂、基性超基性岩的区域控矿作用。     

恩施州富硒区儿童发镉的调查

恩施州富硒区儿童发镉的调查邵器行（中国地质大学,武汉４３００７４）毛大钧苏宏灿（恩施州卫生防疫站,湖北恩施４４５０００）（恩施州妇幼保健院,湖北恩施４４５０００）关键词镉元素的组合效应儿童富硒区湖北恩施Ｃｄ是对人体有害的微量元素。在铅锌多金属硫化物矿...     

玄武岩中刚玉巨晶的包体研究：Ⅰ.更长石包体的发现及意义

本文对山东昌乐碱性玄武岩中刚玉巨晶的更长石包体及同一地区产出的歪长石巨晶进行了电子探针、红外吸收光谱测定,讨论了更长石包体与刚玉巨晶、歪长石巨晶间的成因关系,认为刚玉巨品、歪长石巨晶以及玄武岩中的其他巨晶构成了一个结晶序列,歪长石相对较晚结晶。     

北岭金矿中的针碲银金矿的研究

针碲银金矿产于北岭金矿的晚期矿化阶段，赋存于梳状排列网脉状的石英中，与自然金伴生。矿物组合为针碲银金矿－自然碲－碲铅矿－自然金－石英和针碲银金－碲镍矿－碲铅矿－石英，自然碲，碲镍矿，碲铅矿在针碲银金矿中呈包裹体产出。针碲银金矿呈柱状，板状，粒状晶形，聚片双晶，具强非均质性及双反射和反射多色性，ＨＶ５０＝２１６－２１９ｋｇ／ｍｍ＾２，其化学成分：Ａｇ１０．５８％－１２．３６％，Ａｕ２３．７０％－２４     

多参数无量纲地震前兆信息的最佳提取方法

研究了提取多参数无量纲中，短，临地震前兆信息的４种数学方法，以１９７６年７月２８日唐山７．８级地震周围２５０ｋｍ内１１个计算点的地下水位，水氡，地电阻率，地应力，定点水准，连通管，倾斜仪，伸缩仪和气温等９种资料为基础，计算多参数无量纲地震前兆信息。