Characteristics and genesis of Gangdese porphyry copper deposits in the southern Tibetan Plateau: Preliminary geochemical and geochronological results

Porphyry-type Cu (Mo, Au) deposits have been discovered along the Gangdese magmatic arc in the southern Tibetan Plateau. Extensive field investigations and systematic studies of geochemistry, S–Pb isotopic tracing, together with Re–Os and ⁴⁰Ar/³⁹Ar isotopic dating indicate that the mineralisation of the copper belt is genetically related to emplacement of late orogenic granitic porphyries during the post-collisional crustal relaxation period of the Late Himalayan epoch. These porphyries are petrochemically K-enriched and belong to shoshonitic to high-K calc-alkaline series. They display enrichment of large ion lithophile elements (LILE) Rb, K, U, Th, Sr, Pb and depletion of high field strength elements (HFSE) Nb, Ta, Ti and the heavy rare earth elements (HREE) and Y without Eu anomalies. These characteristics demonstrate that subduction played a dominant role in their petrogenesis and residual garnet was left in the magma sources. Pb isotope data show a linear correlation in the plumbotectonic framework diagram ranging from orogenic Pb in the eastern segment of the copper belt to mantle Pb in the western segment. These constitute a mixing line of the Indian Oceanic MORB with Indian Oceanic sediments and suggest that the porphyry magmas were dominantly derived from partial melting of subducted oceanic crusts mixed with a minor quantity of sediments and mantle wedge components.The Gangdese porphyry copper polymetallic belt has alteration characteristics and zonation typical of porphyry-type copper deposits which include potassic alteration (K-feldspathisation and biotitisation), silicification, sericitisation, and propylitisation. Mineralisation mainly occurs in strongly altered granitic cataclasite at the exo-contact with veinlet-disseminated textures. The porphyries themselves are weakly mineralised with disseminated pyrite and chalcopyrite. The copper deposits contain simple ore mineral associations consisting of chalcopyrite, pyrite, bornite, molybdenite, sphalerite and oxidised minerals of malachite, covellite and molybdite. During supergene oxidation, primary ores underwent secondary enrichment to form economic orebodies with Cu grade ranging from 1% to 5%.Ore sulphides of the copper belt display S and Pb isotopic compositions identical to the ore-bearing porphyries. Their δ³⁴S values vary between − 3.8‰ and + 2.4‰ and are typical of mantle sulphur. The ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb ratios vary in the ranges: 18.106 to 18.752, 15.501 to 15.638, and 37.394 to 39.058, respectively, and yielded radiogenetic lead-enriched signatures. Twelve molybdenite samples from the copper belt yielded isochron ages of 14.76 ± 0.22 Ma and 13.99 ± 0.16 Ma for the Nanmu and Chongjiang deposits and model ages of 13.5 to 13.6 Ma for the Lakang'e deposit. Meanwhile, ⁴⁰Ar/³⁹Ar isotopic dating of two biotite phenocrysts from the Chongjiang and Lakang'e deposits give plateau ages of 13.5 ± 1.0 Ma and 13.42 ±0.10 Ma, respectively. During the geodynamic evolution of the Gangdese collision-orogenic belt, intrusion of the ore-bearing porphyries took place just before the rapid uplift and E–W extension of the southern Plateau. And the ore-forming process may have occurred simultaneously with the uplift and extension (14 ± 0.1 Ma).     

Heterogeneous transition dynamic equations and the self-organized origin of the nesting rhythmic beddings in Panzhihua lithosomes

Dynamic equations were developed for heterogeneous phase-transition in a system of coupled nucleation, growth and ripening. Based on these equations, a self-organized origin of small-scale nesting rhythmic beddings in Pahzhihua lithosomes was investigated and the results showed that the beddings could be formed by the cross supersaturated nucleation-crystallization of augite and feldspar successively. This process could be implemented by coupling with supersaturated nucleation, Ostwald ripening, component diffusion and the primary grain diffusion under a proper temperature gradient. The slightly intensive supersaturated nucleation and Ostwald ripening occurring in Panzhihua lithosomes may relate closely to the mineral components such as V-Ti-Maanetite.     

论东天山土屋-延东(斑岩)铜矿的容矿岩

通过对土屋-延东（斑岩）铜矿容矿岩的时空分布、物质组分及结构构造研究，认为该矿床的容矿岩是一套由中酸性-基性火山岩（包括沉凝灰岩）经富Na、Si热流体交代而成的钠质酸性-基性火山岩，按岩性及结构分以下4类：（1）具斑状或似斑状结构的钠质酸性-中酸性火山岩或称之为钠长石英斑岩与石英斑岩，它常位于矿体的上部，约占容矿岩的20%；（2）以自形、半自形板状、粒状交织结构为主的（含少量斑晶）钠质中酸性-中基性火山岩，或称之为安山玢岩，它常位于矿体的中部及中下部，约占容矿岩的50%；（3）以自形、半自形板状、粒状交织结构为主的富铝基性火山岩，或称之为高铝玄武岩，它常位于矿体的下部及底板围岩，约占容矿岩的20%；（4）以凝灰结构、碎屑结构为主的钠质中酸性-中基性火山碎屑岩，它常位于矿体的下部及底板围岩，约占容矿岩的10%。     

塔里木盆地阿图什—八盘水磨反冲构造系统研究

通过大量野外地质调查和深部物探（地震剖面、MT和重力）综合构造解释，在位于东起八盘水磨，西对乌鲁克恰特以西的南天山前陆冲断带中，确定了阿图什－八盘水磨反冲构造系统及其三角带构造；该反冲系统由小阿图什－八盘水磨和乌尔－喀拉套山反冲构造系统及小阿图什－乌鲁克恰特被变形的反冲构造系统组成；即在以往认为南天山向塔里木盆地大规模中推覆的地区，塔里木盆地美国层第四纪以来沿多组滑脱面向天山新生代造山带反冲推覆。塔里木盆地反冲构造系统发育的区域基底埋深往往大于10km，对应麦盖提基底构造下凹区，而相邻柯坪塔格薄皮推覆构造系统发育的区域基底埋深一般小于10km,对应巴楚基底构造上隆区；逆冲和反冲构造转换带基底埋深约10km,平衡剖面恢复表明弧形逆冲和反冲构造顶部分别为逆冲和反冲位移量最大位置。     

A reduced‐order modeling technique for tall buildings with active tuned mass damper

It is impractical to install sensors on every floor of a tall building to measure the full state vector because of the large number of degrees of freedom. This makes it necessary to introduce reduced‐order control. A kind of system reduction scheme (dynamic condensation method) is proposed in this paper. This method is iterative and Guyan condensation is looked upon as an initial approximation of the iteration. Since the reduced‐order system is updated repeatedly until a desired one is obtained, the accuracy of the reduced‐order system resulting from the proposed method is much higher than that obtained from the Guyan condensation method. Another advantage of the method is that the reduced‐order system is defined in the subspace of the original physical space, which makes the state vectors have physical meaning. An eigenvalue shifting technique is applied to accelerate the convergence of iteration and to make the reduced system retain all the dynamic characteristics of the full system within a given frequency range. Two schemes to establish the reduced‐order system by using the proposed method are also presented and discussed in this paper. The results for a tall building with active tuned mass damper show that the proposed method is efficient for the reduced‐order modelling and the accuracy is very close to exact only after two iterations. Copyright © 2001 John Wiley & Sons, Ltd.     

西藏冈底斯东段斑岩铜钼铅锌成矿系统的发育时限：帮浦铜多金属矿床辉钼矿Re-Os年龄证据

通过对西藏冈底斯成矿带东段的帮浦矿床中的辉钼矿进行Re_Os精确测年 ,首次获得北矿带的铜多金属矿化时间。其Re_Os模式年龄为 (14 .30± 0 .2 5 )Ma～ (14 .75± 0 .2 8)Ma ,5件样品得到的187Re_187Os等时线年龄为 (15 .32± 0 .79)Ma。年龄数据与冈底斯成矿带东段南侧斑岩铜矿化带的矿化时间 (14Ma左右 )具有一致性 ,表明北矿带的成矿作用与斑岩有关。斑岩成矿是冈底斯成矿带内的一次主导成矿事件 ,冈底斯南矿带以斑岩型铜钼矿床为主 ,其北矿带以斑岩型铜铅锌多金属矿床为主。冈底斯南、北矿带的成矿作用具有统一的成矿动力学背景 ,发生在碰撞造山带侧向伸展时期 ,均为陆_陆碰撞造山带演化过程中同构造岩浆活动期的产物     

Distribution and temporal variation of cadmium in the St. Lawrence river basin

Samples of raw water were collected at regular intevals at two transects in the St. Lawremce River and four of its tributaries from March to November 1991 and from April to June 1992. Water samples were analyzed for both the dissolved and the particulate phase for cadmium (Cd), organic carbon, iron and manganese. Mean dissolved Cd concentration was 10±5 ng/L and no spatial variability was observed. Higher concentrations were found during high flow periods, suggesting an uptake of cadmium by phytoplankton during summer. In addition, dissolved cadmium did not appear to be associated with either DOC, dissolved Fe or dissolved Mn. The mean particulate Cd concentration was 1.3±1.1 μg/g, with almost all stations presenting the same concentration except the Yamaska River, which had a concentration of 0.5±0.2 μg/g. Particulate Cd showed a negative correlation with suspended particulate matter and a positive correlation with particulate organic carbon and particulare manganese. Fifty-nine percent of the cadmium was found to be in the particulate phase. Partition coefficients for cadmium (Kd), organic carbon (Kc), iron (KdFe) and manganese (KdMn) were calculated for each sample. Log Kd varied from 3.9 to 5.9, with an average of 5.0±0.4. Log Kd decreased with increasing particulate, matter as did Log Kc and Log KdMn. No significant correlation was found between Log Kd and Log Kc, suggesting that the distribution of cadmium between the dissolved and the particulate phase is not influenced by the distribution of organic carbon. In contrast, positive correlations were observed between Log Kd, Log KdFe and Log KdMn. Cadmium distribution appears to be influenced by Fe and Mn distribution.     

微团聚体分析在工程地质研究中的应用

微团聚体是天然粘性土的基本结构单元, 微团聚体的组成、水稳性和强度是粘性土工程性质形成的重要原因。本文通过对黄土与海相软土这两种典型的粘性土颗粒分析与微团聚体分析结果的对比, 研究了水稳性与非水稳性微团聚体的形成原因, 并在此基础上探讨它们的工程特性的形成。     

江苏丹徒前黄水泥配料粘土矿床矿石工业利用试验研究

系统了介绍了生产水泥的石灰石，下蜀粘土，硫酸渣三组分配料的工艺性能试验成果，提供了一套有关采用现代水泥工艺生产出符合ＡＳＴＭ的Ｉ型水泥的试验数据，同时，其试验成果可代同类矿床勘探借鉴。     

北山地区大口子片麻岩 Ar-Ar 年代学初步研究

对甘肃肃北县境内的大口子片麻状石英闪长岩中的角闪石、黑云母、斜长石进行了 Ar-Ar年龄测定，分别得到角闪石、黑云母、斜长石高温坪年龄 1872.3±14.8Ma、1823.2±13Ma、1748.5±13.5Ma。它们分别代表了同一片麻岩中不同矿物的早期形成时代。角闪石、黑云母、斜长石的中温坪年龄分别为952.7±8.4Ma、862.8±6.2Ma\678.2±4.8Ma，分别代表了同一岩石中不同矿物记录的后期热事件年龄，其表明同一岩石中不同矿物给出的不同年龄值，显示了不同矿物具有不同的40K-40Ar