摘要
根据质量、动量和能量守恒定律，建立控制微分方程组．运用有限元方法，求解数学模型．得到了热流体运移的流函数和温度分布值，进而求出流速及热流值，将上述理论应用于沙溪矿区成矿过程中温度场和流体场的研究，取得了满意的计算模拟结果，为进一步研究斑岩铜矿的形成过程，提供了有意义的信息．
Shaxi porphyry copper (gold) deposit is located at Tanlu fault belt. According to the data of geological setting and regional geophysics, and the detailed study on oredeposits and the measurement results of fracture abundance, the conceptual geologicalmodel and permeability distribution model have been proposed.Using these models, thepresent authors have simulated the temperature and fluid flux field around the coolingpouphyry apothysis. According to the laws of conservationof mass, momentum andenergy,a set of governing differential equations that represent migrating process ofhydrothermal fluids have been established. The distributions of streamfunction and temperature are obtained from the numerical solutions to these equations by using the finite element method. Darcy velocity and heat flux can be further calculated.The method stated above is applied to the studies on the ore-forming process of Shaxiporphyry copper (gold) deposits for calculating the distribution of temperature and fluidflux field. A satisfactary result has been obtained, which will offer important information tothe further study of o￣forrning process of porphyry copper deposits. In comparison withthe;previous study results, the present Study has improved on the permeability distributionmodel, and on the means of selecting parameters and of acquainting the numerical solutionof differential equations. A ameliorated comuter code has been established to simulate thet6mpefature and fluid flux field around cooling intrusive body. Applying the camputer codetO calculate the temperature and temperature gradient, the acquainted results are well inagreement. with the determinated data by geothermometers.The results of computer simulating for temperatrue field have shown that the effect ofsmall porphyry apophysis on the temperature field only lasts for a relatively short time, themajor energy source came from the bathylite at deep level. The convection made theheat-dispersion, whichis controlled by the high permeability of wall rocks. In order tomaintain the appropriate temperature for a long time during the ore-forming process, themultiple pulses of intrusive magma were necessary. Although it was difficult for a smallapophysis to remain in the high temperature field for a long duration, the bathylite at deeplevel could result in a heat-.anomaly around the porphyry for over 10'years, even morethan I Ma. So in the 13ie evolution stage of the hydrothermal system, meteoric water wasdominant and played an important part. According to the calculated results for the fluid flux field, the permeability (or fractureabundance) was a major factor affecting the fluid flux, the flux of ore-forming solutioncentred the mineralized porphyry and produced the temperature and density gradient,which caused'the convecfon. The place which possesed high permeability and streamline- controlled the distributionof productive ore bodies. From the maximal Darcy velocity oflynx ic￣cm s--', the calculated total amount of hydrothermal solution which passedthrough the porphyry and its peripheral areas in 10'years was 1.5768 × 1010m3. If the solubility of the copper in the hydrothermal solution was 1￣ 10 × 10-6(1-10ppm), the totalamount of migrated copper which derived from the wall rocks was 15768 to 157680 tons,corresponding to one-fifth or one-fiftieth of the total amount of enriched copper in theminerazited area, but the migrated copper from wall ricks would be diffcult to become theingredient of the enriched copper, which would be decided by the physical-chemicalparame.ters of the hydrothermal system. This study has shown that the Shaxi porphyrycopper deposits originated through the aCtion of magmatic water, and belonged to the typeof magmatic hydrothermal ore deposits, which is in concert with other detailed study results regarding the genesis of the porphyry copper (gold) deposit.
出处
《南京大学学报（自然科学版）》
CSCD
1994年第2期295-303,共9页
Journal of Nanjing University（Natural Science）
基金
国家自然科学基金
博士点基金
关键词
斑岩矿床
铜矿床
成矿过程
热液体
porphyry copper
heat fluid transport
finite element
computer simulation
