摘要
本文以成矿系统理论为指导,应用区域成矿研究法,对浦城—宁德北西向成矿带内的控矿构造基本格局及对矿床的控制作用,矿床主要类型及其各类型矿床的产出地质背景、控制因素及形成机制,以矿床分布规律与找矿方向等进行了较深入的研究与分析,取得主要成果如下:
1、该成矿带内控矿构造型式多样,控矿作用层次清晰。深部构造,在幔凹或幔凸的边缘、莫霍面等深线密集(梯度较陡)或局部突出地段、扭曲端等控制区域成矿带的展布;大断裂带及其复合部位控制矿集区和大型矿床的产出;大断裂断陷(隆)构造,即隆中坳,或总体坳陷(断陷)背景下的局部隆起,即坳中隆,或总体坳陷的背景下的局部更为强烈的坳陷,即坳中坳,所有这些特殊的构造部位,往往也是成矿元素的富集区和成矿远景区。不同级别的火山与侵入构造分别控制矿田、矿床和矿体的产出。
2、带内矿床主要可归入①与晚元古代海底火山—沉积变质改造型(中生代)铜、铅锌、铁、金矿和②与中生代火山—侵入热液活动有关的钼、铜、铅锌、金银矿两大成矿系统。其中前者的块状硫化物型铅锌、铁、铜矿床和后者中的斑岩型铜钼矿为区内找矿的主攻类型。Cu、Mo、Pb、Zn、Au为区内优势矿种。
3、对赤路钼矿床的Re—Os同位素年代学研究得出如下结论:(1)赤路钼矿的矿化模式年龄为105.6Ma,与似斑状花岗岩、二长花岗岩等的87Sr/86Sr等时线年龄115±4Ma较接近,表明二者在成因上密切相关,同属燕山晚期岩浆演化的产物;(2)赤路钼矿床具有辉钼矿中Re、Os含量偏低,低87Sr/86Sr初始值和硫同位素组成接近陨石硫等特点,表明其为成矿物质来源于地壳深部,且为斑岩型钼矿床。该认识将为浦城—宁德北西向成矿带乃至於全省燕山晚期岩浆活动及成矿提供了可靠的年代学证据和指导。
4、对政和夏山铅锌矿床的研究,结合研究省内主要矿化集中区马面山群对金银铜铅锌多金属矿的控矿特点,得出如下结论:(1)新元古代马面山群是带内重要的块状硫化物型铅锌、铁、铜矿的赋矿层位,尽管后期受到构造、热液的叠加改造,其层控特点仍相当清晰,成矿主要发生在新元古代;(2)从目前的研究结果而言,铜、铅锌、铁矿的成矿作用主要受绿片岩及大理岩等钙硅质岩控制;(3)带内马面山群出露区及其周边,具备寻找大型海底火山(沉积)变质改造型(块状硫化物型)矿床的潜力。
5、根据上述认识,结合矿床、矿(化)点、物化探及重砂异常等发育情况,共筛选出成矿远景区5个、预查找矿区6个及普查找矿区7个,为进一步找矿突破提供依据。经初步钻孔验证已有所发现。
With the theory of metallogenic system as a guide and the application of regional metallogenic study method, this research are thoroughly carried out in the aspects of the tectonnic setting of the NW-strenching Pucheng-Ningde metallogenic belt, its ore controls, main types of ore deposits and the gennesis of each type, as well as the metallogenic regularities and prospecting direction. Through the work of the past three years, the main accomplishments obtained are as follows:
1. multipe scale and multiplicity of ore controlling structure. Deep structure in the mantle concave or convex edge of mantle, Moho-discontinuity isobath (steep gradient) or local turning control the regional metallogenic belt in distribution; major fault zones and their recombination region control the metallogenic zone; great fault depression, that is, overall depression in the context of uplift, that is, or local uplift in the background of overall fault depression, or the local stronger depression in the background of overall fault depression, all of these special structures are often the enriched areas of ore-forming elements and potential prospects. Different levels of volcanic and intrusive structure control the orefields, ore deposits and orebodies, respectively.
2. The main ore deposits within the belt can be divided into two metallogenic syetems :①.Neoproterozoic submarine volcano-sedimentary metamorphic transformation m.s.( of copper, lead and zinc, iron, gold deposits) and②. molybdenum, copper, lead-zinc, gold and silver deposits related to Mesozoic volcanic-intrusive hydrothermal m.s. The massive sulphide, lead-zinc, iron, copper deposits of the former and the porphyry copper-molybdenum deposits of the latter are the main ore types in the region.
3. The conclusions drawn through the research on the Re-Os isotopic geochronology of the Chilu Mo deposit are as follows: (1) the model age of the Chilu Mo ore deposit is 105.6Ma, closely to the 87Sr/86S isochrone age of the porphyric granite, adamellite. So they are closely correlated in the genesis, and both are the production of magmatic evolution of the late Yanshan. (2) In the Chilu Mo deposit, the Re and Os content and the initial value of 87Sr/86S are on the low side, and the sulfur isotope is close to that of meteorite, indicating that the ore-forming substance comes from deep crust and the type is porphyry Mo deposit.
4. The research on Xiashan leac-zinc deposit in Zhenghe, combining the ore-controlling characteristics of Mamianshan group in the ore concentration area of the belt. The results are as follows: (1) Neoproterozoic Mamianshan group is important ore-bearing horizon of massive sulphide lead-zinc, and copper deposit. Although undergoing the superimposed reconstruction of the structure and fluid, its stratabound characteristics still show clear. The mineralization occurred in Neoproterozoic. (2)From the current research results, the copper, lead-zinc, iron deposits are mainly controlled by greenschist and marble and other kinds of calcareous and siliceous rock. (3) the outcrop area of the Mamiansha group and its circumference in the belt has the potential of prospecting large-sized submarine volcano-sedimentary metamorphic transformation deposit.
5. According to ore-forming geological setting, ore-controlling factors and the ore prospecting indicators on the main types of the ore deposits, combining the geological, geophysical and geochemical data and the heavy mineral anomalies, five metallogenic prospecting areas, six preliminary exploration areas and seven reconnaissance areas are sifted for the further ore-prospecting.
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