摘要
研究了粤北4292km2内1448个基岩样品的35项元素、安徽省江南江北各约22000km2和18100km2内5489个和4524个水系沉积物样品的14项元素、塔里木盆地5个含油气区的7419个土壤样品的酸解烃(C1～C5)、蚀变碳酸盐、紫外、荧光等油气地球化学指标值的面积校正累计频率(ACAF)特征。研究表明,地球化学指标值的ACAF均显示连续多重分形特征,而且具两种特定模式:简单连续多重分形(SCM)模式和具高浓集的连续多重分形(HACM)模式;主要成矿元素和主要油气化探指标均不同程度地显示为HACM模式,而其他指标多表现为SCM模式。不同的分形模式可望用于区域含矿含油性和区域环境评价,而开始出现高含量叠加的“临界”含量值可能作为区域成矿成油强度的一种度量。
A method based on area calibrated and accumulative frequency (ACAF) distribution of geochemical data from three metallic and five oil/gas geochemical fields is proposed to study fractal characteristics of geochemical fields. The data include 35 elements of 1448 whole rock samples from a region of 4 292 km2 in North Guangdong Province, South China, 14 elements of 5 489 and 4 524 stream sediments in South and North Anhui Province, South China, respectively, and more than 15 hydrocarbons and other indices in 7 419 soil samples from 5 oil fields with total survey area > 8 000 km2 in the Tarim basin, North China. The results show that log log diagrams of ACAF of geochemical indices clearly demonstrate that geochemical fields are of continuous multifractal features,!which are quite different from the results of some authors who showed that geochemical dispersion of indices bear unifractal features as single power law relationship on log log diagrams. The curves of ACAF on log log diagrams can be approximately fitted by two straight lines. The first one covers the relatively low concentration portion and reflects the fluctuated detection limit of measurement, and the other covers the major concentration region and represents the intrinsic multifractal characteristics of geochemical fields. There does not exist any turning point but rather a continuous transition section between them and the intersection cannot be used as a threshold to distinct anomalies from geochemical background. The continuous multifractals of geochemical fields can be categorized by two models: simple continuous multifractal model (SCM) and highly accumulated continuous multifractal model (HACM). Main ore forming elements and major oil indices show HACM to different degrees, while others SCM. These different fractal models are expected to be applicable to appraise regional ore bearing and or oil bearing strata and even regional environment. Whereas, the threshold occurring in highly accumulated part will be useful to measure ore forming or oil forming strengths. Continuous multifractals are quite universal in geochemical fields.
出处
《地球化学》
CAS
CSCD
北大核心
2002年第2期191-200,共10页
Geochimica
基金
国家自然科学基金重点项目(49633120)
国家教育部博士点基金
