Table of Content

20 June 1998, Volume 4 Issue 2

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Article

RELATIONS OF GOLD ABUNDANCE IN THE GRANITES AND STRATA TO GENESIS OF GOLD DEPOSITS

Hu Shou-xi1， Chen Fu-jing1, Xu Jin-fang2, Guo Kang-heng2, Li Shi-mei3

1998, 4(2):  121-126. 

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The hydrothermal deposits of gold in North China Platform are commonly associated with granites and metamorphic rocks or strata in the greenstone belts, which are thought to be the source of gold by many geologists. Their hypotheses are founded on the higher abundance levels of gold in these rocks or strata celled as source rocks end source beds to support their theories that the gold was derived from these granites or strata to form deposits. Owing to the improvement of quantitative measuring method, many analytical data for gold with reasonable accuracy (0.1×10-9)accumulated. It shows that the gold abundance in the metamorphic rocks or strata is rather low, (1.06～ 2.3× 10-9 in average), and in the relevant granites is only 0.6～ 1.4×10-9 in average. The gold content decreases with increasing granitization and migmatization or amount of fe1sic minerals. This shows that the source rocks or source beds are ambiguous and nonspecific. The granite-formation end alkali-metasomatism are the main mechenism for mobilization of gold which leads to formation of gold deposits.

STABLE CARBON ISOTOPE COMPOSITION AND DESORPTION-DIFFUSION EFFECT OF THE UPPER PALEOZOIC COALBED METHANE IN NORTH CHINA

Qin Yong, Tang Xiu-yi, Ye Jian-ping

1998, 4(2):  127-132. 

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The stable carbon isotope of the shallow Upper Paleozoic coal bed methane (CBM) in North China is generally more various in value and lighter in composition than those of the normal humic-type natural gas, and approaches to or falls in the range of the norm al humie-type gas in the stage of the high-rank coals. This might be primarily originated from the CBM desorption-diffussion effect overlapped upon the thermodynamical isotope fraction mechanism, which resulted in the vertical zoning such as the primary, transitional and desorbed zones. The depth limits among different zones are various with districts, which is associated with the depth of CBM weathered zone and the rank of coal reservoirs, i.e. the deeper the weathered zone, the deeper the desorbed zone, and the higher the coal rank, the shallower the desorbed zone. As for the gas coal reservoirs, the primary zone is deeper than 1500m, the transitional zone is located between 1500m and lO00m, and the desorbed zone is shallower than lO00m. In the high-rank (meagre coal and anthracite) Coal reservoirs deeper than the weathered zone, there is hardly the stable carbon isotope fraction be cause the absorbability of the coal organic matters to CBM increases greatly. Furthermore the coalbed methane in the middle-rank coal (flame to lean coa1) reservoirs that have been explored was almost migrated and had the desorption-diffusion origin. The study on the desorption-diffusion effect above-mentioned is helpful to the evaluation of the CBM-accumulated conditions in North China. If some geological controls such as the tectonic evolution, combed-buried history and covering strata were favorable to the CBM preservation, the desorption-diffusion effect might be favorable to the CBM accumulation. Conversely, the coalbed methane might escape substantially.

PETROLOGICAL CHARACTERISTICS OF SHILING ALKALINE COMPLEX, CONGHUA, GUANGDONG PROVINCE, AND ITS GEOLOGICAL IMPLICATIONS

Xiao Zheng-yu1, Wang Li-ming1, Yang Xue-ming2, Yang Xiao-yong2

1998, 4(2):  133-138. 

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On the basis of detailed geological investigation and mapping, this paper studies the petrological features of Shiling alkaline complex, Conghua, Guangdong Province. Which is mainly composed of nepheline-hornblende syenite, hornblende syenite and biotite syenite. The alkaline complex is formed by granite fractionation, occurs in intraplate extensional tectonic setting and is related to deep fault. It is significant that the complex itself is a nepheline syenite mineral deposit of industrial and economic values.

INQUIRY ON THE GENESIS OF GROUNDWATER WITH HIGH FLUORIDE IN FENGXIAN PEIXIAN AND TONGSHAN COUNTIES OF JIANGSU PROVINCE

Zhaog Jing-roog1, Zhu Fa-hua1, Chen Ru-xiu2, Miao Xiao-tu3, Yao Su-ping1

1998, 4(2):  139-146. 

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This region is demonstrated as a geochemical region with high fluorine through studies on the fluorine contents of soils, magmatic rocks and the Archean-Cenozoic strata geochemical profile. It is clarified that the Archean-Proterozoic ancient rock series with high fluorine in the Taishan-Yimenshan uplifted region is the material source of soil sediments, and that the Yellow River flood and heap many times (absorption of fluorine by clay minerals)accumulates and adds fluorine content in the soils according to heavy mineral comparative study and topography analysis. The study reveals that the water dissolved fluoride content in soils of this region is relatively high The fluorine is transferred into groundwater through natural water leachate and groundwater soak; and fluorine accumulation forms high fluoride groundwater region in sunk region of low-lying land between rivers because of water stagnation and evaporation concentration.

RESEARCH ON THE BASALT-NUCLEI OF POLYMETALLIC NODULES FROM THE EAST PACIFIC BASIN

Kang Xian-gui1, Kang Chang-sheag2, Yang Rong-yong3

1998, 4(2):  147-154. 

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The knowledge of core material of polymetallic nodules is of great importance for clarification of the distribution and origin of nodules in ocean. Based on dissection of about 178 pieces of samples of polymetallic nodules obtained from the Fast Pacific Basin by investigation ship “HAIYANG 4” of MGMR among which 53 pieces are basalt-nuclei in composition, accounting for 29.8%, this paper comprehensively studied and analyzed the features of these basal-nuclei of nodules, including lithology, petrochemsitry, mineral constituents, trace-element geochemistry and isotope chronostratigraphy, etc. The authors come to a conclusion that the basalt-nuclei of nodules belong to ocean island tholeiite or alkali-basalt. There are of calc-alkaline series and alkali series, which include olivine, tholeiite, and alkali basalt, and they were mainly formed in the Tertiary. In the light of studies of the or in of basalt-nuclei of nodules, and analysis of the relationship between the basalt-nuclei and the distribution of ploymetallic nodules, the authors pointed out that basalt-nuclei of nodules are derived from seamount basalt in the study area. It is found that seamount basal mainly effected and control1ed the formation and distribution of polymeta11ic nodules, which provied enormous nuclei.

EXPERIMENTAL RESEARCH ON RHEOLOGICAL BEHAVIORAS OF LOWER CRUST AND ITS SIGNIFICANCE OF TECTONIC EVOLUTION IN THE JUNCTURE AREA OF SHANXI, HEBEI AND INNER MONGOLIA PROVINCES, CHINA

Zhao jing1, Liu shun2

1998, 4(2):  155-167. 

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High-pressure and high temperature experiments on basic and acid granulites sampled from the juncture area of Shanxi and Hebei and Inner Mongolia provinces show that, steady-state flow law obtained from these two kinds of granulites are ε=20.7exp(-288/RT)×△σ3.0 andε=10^6.59exp(-425RT) △σ3.02 respectively, and can be correlated with those from granulites exposed in Canadian continental shield. Under the condition of temperature at 700～1000℃ and confining pressure at 1.0～1.2GPa and strain rate at 10^-14S^-1 concerning lower crust, experimental rocks deformed in mainly ductility and ductile shear zones developed in some rocks. Pyroxene and feldspar are subject to undergoing dynamic recrystallization and oriented in lineation, while quartz was in static recovery. The result above can match with that observed from the field. The macro-rheology-models of lower crust show that one or more thicker lower-creep-strength-layers exist in lower crust with regard to thicked lithosphere as well as in upper mantle with regard to thinned one. Rheological behaviors of continental lower crust characteristic of lower-creep-strength layer of this kind can help lead to thicking and thinning of lithosphere.

TECTONIC SETTINGS OF ONDOR SUM GROUP AND ITS TECTONIC INTERPRETATION IN ONDOR SUM REGION, INNER MONGOLIA

Wu Tai-ran, Zhang Chen, Wan Ji-hu

1998, 4(2):  168-176. 

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There is a set of metamorphic rocks in Ondor Sum region, Nei Mongol, which was named as Ondor Sum Group and its age was considered as Paleozoic before. Tow major assemblages of the Group can be recognized. One is outcropping at Wulangou and consists of metamorphic pillow basalt, clastic rocks, silicalite and other epimetamorphic rocks. The other is outcropping at Deyanqimiao and consists of plagioamphibole, plagiogneiss and other hypometamorphic rocks. The assemblages are different from each other in metamorphism, deformation and petrologic chemistry as we1l as the tectonic settings. The results of this study demonstrated that the volcano-elastic assemblage was formed in back-arc basin, and the hypometamorphic assemblage was the underplatting product during extention in the region. Recognization of the DNO assemblages has an important significance for the tectonic evolution of the northern margin of North China Plate. According to the recent isotopic chronological data, the ages of two assemblages are all Neo-Proterozoic. The Sm-Nd isotopic age of the volcano-elastic assemblage is 807～961Ma, and the hypometamorphic assemblage is about 638Ma. The rifting began in the Meso-Proterozoic at northern margin of North Chins Plate. At the beginning of the Neo-Proterozoic, there was a series of island arcs separated from the North China Plate and back-are basin occurred at the same time. The volcano—elastic assemblage were formed in this period. Another extensional cycle began at the end of the Neo-Proterozoic. The hypometamorphic assemblages were formed in the magmatic passive margin during underplating. Since the major assemblages of the Ondor Sum Group are the products of different stages in tectonic evolution of North China Plate in Neo-Proterozoic, the tectonic evolution in the Paleozoic must be reconsidered.

PETROGENESIS AND THERMAL HISTORY OF XI XIONGWEN INTRUSION, DABIESHAN: INSIGHT INTO SHAPING PROCESS OF WESTERN DABIE THERMODYNAMIC DOME

Xu Chang-hai, Ma Chang-qian, Yang Kun-guang, Lia Gui-yu

1998, 4(2):  177-188. 

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Petrologic, geochemical, structural, geological and thermochronologic data show that Xi Xiongwen intrusion belongs to the remelting synuplift-adamallite, which stemmed from its metamorphic-country rocks. And the inclosed structure surrounding this intrusion is regarded as the thermodynamic dome that results from uplift of western Dabie block and magmatic diapirism associated with it. The process of forming and emplacement for the intrusion provides useful and indispensable constraints on the shaping-process of the thermodynamic dome. The study suggests that the equal-mass remelting process leads to volumetric expansion which is 1.2 times as much as the volume of metamorphic-country rocks, that the slowly cooling process(4.4℃/Ma)and emplacement of the intrusion that coordinate country rocks force the thermodynamic dome to shape under the surface of 15.2 km in 161.5 Ma, and that the minimum height of the dome is about 5 km. As a result, such information as the nature of the remelting process, the value of volumetric expansion, the intrusive velocity, the coling process, the crystallization depth and the emplacement-age etc. of the intrusion can help understand further or depict quantitatively the shaping-process of western Dabie thermodynamic dome which is a typical structure during Dabie-block slowly uplifting in Mesozoic era.

STUDY AND MANAGEMENT OF GEOLOGICAL ENVIRONMENT PROBLEM IN NANJING CITY

Luo Guo-yu, Li Xiao-zhao, Zhang Chun-hua, Salah Bishir

1998, 4(2):  189-197. 

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Environment problem is now a worldwide hot-focus. In this paper, the authors suggest that pollution and destruction of ecosystem and environmental geotechnical engineering problems are two kinds of environment problems confronted by human society. Based on the characteristics of Nanjing geological environment, the authors studied some major environmental geotechnical problems. The results of this study could provide further knowledge of environment problems in Nanjing and are useful for the regional economic development.

NUMERICAL SIMULATION FOR PREDICTED PUMPING OF GROUNDWATER RESOURCE IN ZIBO NYLON PROJECT, SHANDONG

Yan Xue-yi1, Zhu Guo-rong2, Wang Hao-ran2

1998, 4(2):  198-204. 

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The groundwater pumping experiments have been successfully simulated in the well field of Wangwang-Zhutai of Linzi district, Zibo city, Shandong province, where ground water is used as a resource in the engineering project of nylon production. This simulation is based on the completion of the hydrological model of that particular area after a thorough investigation. The authors combined the Ritz definition of finite element method with the simplex linear programming to predict dynamically the condition of the groundwater under two different kinds of precipitation for the next 10 years. The results of this study could in turn provide reasonable design for the water supplying system of the nylon industry.

COMPREHENSIVE ENVIRONMENTAL IMPACT ASSESSMENTS AND COUNTERM EASURES OF TOURISM

Wu Chang-nian1, Zhou Ting-xu1, Wang Qin-geng1, Tang Liang1, Liu Guang-min3, Ling Hong2

1998, 4(2):  205-211. 

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Tourism has negative and positive impacts on natural environment. Negative impacts include effects on water and air environment, plant and animal, soil and done erosion, and aesthetics. Statistical results of monitoring data for the air environmental quality of Maoshan tourist site of both before and after exploitation have shown that tourism has negative impacts on air environmental quality. Statistical result and evaluation results of monitoring data for the water environmental quality of Changdanghu tourist site of both before and after exploitation have also shown that tourism has negative impacts on water environmental quality. Positive impacts include establishing natural protection are as protecting ocean, vegetation and wetland, encouraging marginal land development and educating the masses. To ensure a permanent and sustainable tourism industry, countermeasures are: alternative tourism, environmental planning for travelling areas, experimental track for the environmental impacts of tourism comprehensive research model for the cumulative environmental impacts of tourism.

ANALYSIS OF ENVIRONM ENTAL EFFECTS OF NANJING XUANWU LAKE SUBAQUEOUS HIGHWAY TUNNEL

Ni Hong-ge, Li Xiao-zhao, Luo Guo-yu

1998, 4(2):  212-219. 

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Nanjing Xuanwu Tunnel, a subaqueous highway tunnel in the centre of the city is a typical geoengineering project in vulnerable environment. The factors which affect construction of subaqueous highway tunnel include not only environmental engineering geology conditions, such a5 variation of soil horizon, distribution of lenssoid body. 1iquefaction of sand, soft soil loss and engineering water hazard, but also urban environment restrain factors, such as cultural landscape, scheme of metro engineering, high buildings and underground line. Furthermore, construction of the tunnel will produce negative effect on urban environment, such as surface subsidence, waste accumulation, variation of water environment, damage of underground pipes and lines and cultural landscape, water contamination and noise pollution, etc. Based on the principle of systematic engineering, the authors analyzed the above problems and evaluated the best tunnel entrance schemes and the best tunnel construction schemes.

TENDENCY ANALYSIS OF THE INTERACTION BETWEEN GROUDW ATER AND BASALT

Ai Yao1, Gao Ming2, Dai Shui-han2

1998, 4(2):  220-228. 

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A model of hydrochemical equilibrium reactions is proposed based on the principle of equilibrium of complex actions in the solution, and used to calculate the concentrations and activities of different mineral species in groundwater. The index of mineral saturations related to the groundwater are then determined. So the tendency of dissolution and precipitation of minerals in the hydrorock reactions can be studied. This method was applied to study the basalt in Xuyi county, Jiangsu province and discuss the reactions between groundwater and basalt.

KEY TOPICS ON PHYSICS AND EVOLUTION OF THE EARTH’S INTERIOR: Ⅲ. OUTLINE OF MICROGEOPHYSICS

Chen Sheng-zao

1998, 4(2):  229-239. 

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Microgeophysics is a new branch of the Earth sciences, which is deliberated on a basis of microphysics, aimed at studying, by means of theoretical, experimental, numerical and computer’s modeling, the physical properties of the Earth s interior, geologic bodies and various rocks that make up the Earth. The areas covered in this context include rheology of the lithosphere and the mantle, predominated by multimicrophysics mechanisms, dynamic friction of rocks and the brittle-ductile transition in the crust, focal mechanisms concerning the mechanics of earthquakes and faulting, fluid-rock interactions, acoustic emissions/microseismic activity, theory of acousto-ultrasonics and geologic application, and so on. It is an important research direction in microgeophysics to establish an integrated, comprehensive, and parameterized model, coupling physics, chemistry, rock mechanics, and thermal science with dynamics, for unstable osmotic media. Its immediate effect on economics and societies will keep abreast of both environmental geophysics and environmental geochemistry, there appear to be certain uncertainties in understanding the Earth’s interior, some topics such as the movements of tectonic plates, the deep mantle wellings, and even microcracks and shear sliding of faults, may be also involved in the applications of fractal and chaotic theories. As an objective it must be a necessary step to combine the micro-with the macrogeophysical methods and keep them to be consistent in approaching a final solution to the problems in the area.

DISCOVERY OF THE MIDDLE JURASSIC STRATA AT N0RTH TIANZHU, GANSU EAST PART OF N0RTHERN QILIAN M0UNTAINS

Sun Bai-nian, Ma Jin-long

1998, 4(2):  240-240. 

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