华北地台北缘金矿成矿带的构造－水文特征

TECTONIC-HYDROLOGIC CHARACTERISTICS OF THE GOLD METALLOGENIC BELT ALONG THE NORTHERN MARGON OF NORTH CHINA PLATFORM

本文在矿石包体稳定同位素实测资料基础上编制了研究区成矿溶液δＤ等值线图，表明该成矿带内多数矿床在大气降水参与成矿过程方面具有整体性和统一性。计算各个成矿系统的水岩比后，根据其在δ￣（１８）Ｏ－δＤ坐标系中的位置可发现：成矿带多数矿床分属３个构造－水文成矿系列——每个系列是由一组相对富岩浆水的成矿流体矿床为内核；一组相对贫岩浆水的矿床为外围围绕该核心。基于对各个成矿系统流体演化成熟度的计算，提出一种预测、评估矿床规模的构造－水文方法。

Lying 100°～130°east longitude and 38°～43° north latitude, the EW-trending gold metallo-genic belt along the northern margin of North China platform,a belt 2000 km in length and 100km in width,consists of more t han one hundred hydrothermal gold-silver deposits. Wall rocksinclude Archean and Proterozoic metamorphic rocks as well as Mesozoic granite and volcanicrocks. In the past,controversy existed concerning such ore-forming problems as hydrothermaltypes and metallogenic epochs of these ore deposits,and even of one deposit. Based on measured data of some 500 inclusions in ores from over 40 deposits,the author hascompiled a deuterium contour map for the study area. The distribution of deuterium might be ex-plained by Mesozoic paleogeography.It can be seen from the diagram that varied ore depositsshow an integrity and unity in the ore-forming process of meteoric water. On the basis of calculated water-rock ratio of each ore-forming system and its position in theδ￣(18)O-δD coordinate,the author has found that ore deposits of this gold metallogenic belt mightbe divided into three metallogenic series,with each series composed of a core and a periphery,suggesting that ore deposits formed by ore fluids rich in magmatic water are located at the core,and lots of ore deposits formed by ore fluids deficient in magmatic water make up the peripheryaround the core. There seems to be regularity in the arrangement of the three metellogenic se-ries:from the inland to the epicontinental area,ore-forming temperatures increase from 275℃through 190℃ to 300℃,and metallogenic epochs change correspondingly from old to young,i.e. from J_1+J_2 to J_3+K. As Blattner(1985)designed a method for hydrologic evolution of active geothermal systemon the basis of isotopic(hydrogen, oxygen etc.)drift,the author used hydrologic evolution topredict reserves of gold deposits which serve as the fossil geothermal system;as a result,somevaluable results were obtained. In summary,the frame put forward by the author with the emphasis on hydrogeology en-ables geologists to understand individual ore deposits in the light of regional hydrogeology of themetallogenic belt as a whole.