马鞍桥微细浸染型(沉积岩容矿)金矿床(体)快速定位预测研究

On the rapid-positioning and prediction for micro- dissemination type (sedimentary rock host) gold deposit (ore bodies),Ma′anqiao

该矿床是华北板块南缘秦岭——“中央造山带”产于沉积岩系中的重要金矿床之一 ,Au的主成矿期为“沉积变质期”。成矿作用演化自早古生代始至印支—燕山期 ,伴随板块构造逆冲带的发展 ,经历了漫长的“沉积 (矿源 )→变质 (矿胚 )→岩体热量影响 (中温成矿元素叠加 )→逆冲推覆、走滑脆—韧性剪节 (矿体成型、初步定位 )→伸展构造 (破坏矿体、最终定位 )演化的历程 ,与脆—韧性剪切带密切相伴”。应属板块构造逆冲带浊积岩 -剪切带型层控金矿床 ,其快速定位预测标志具普遍性指导意义。

Ma′anqiao gold deposit is one of mast important gold deposits, occurring in sedimentary strata, in the middle-west part of Qinling——“Central Orogen”, China and reaches into a large scale in reserves; and its potential of resources adds year after year The gold deposit has typical significance in the metallogenic mechanism and evolutionary pattern and can be compared with well known gold deposits of the samp type at home and abroad Major achievements of the study are as follows 1 It is clearly pointed out that the metallogenic geotectonic environment of Ma'anqiao gold deposit is located at the plate obduction zone in the fore arc basin on south margin of North China plate The major interface of Shang-Dan fault belt on south margin of North China plate is removed southward 10 km away, lying on the Banfangzi-Xiaowangjian line, sharply distincting from formerly northern margin of Yangtze plate 2 The age of ore bearing rock series 'Wangjiahe Fm ', being certainly confirmed, could be attributed to the early Paleozoic Era rather than the Devonian Period, being concluded before 3 The Danfeng Gr Microlithon(Pt 3-P Z1 dn) and Dacaotan Gr Microlithon(D 3) have been breaked up from the formerly-designated Davonian Wangjiahe Fm , therefore, the existence of the partial carboniferous system has been denied; the new regional stratigraphic sequence has been reordered and the new appearance(P Z1 wj) of ore bearing rock series “Wangjiahe Fm ”has been set up on the basis of two suits of conglomerate In addition, it is further expounded that Wangjiahe Fm should belong to a series of turbidite of the deep water clinoform facies and is a component part of the important geological body on south margin of North China plate, which is formed by several microlithons overlapped 4 Described in detail that the metallogenesis of Au in gold deposit of this type underwent, from the early Paleozoic to early Yenshan time, a very long evolutionary course, i e “Sedimentation(source of ore)→Reformation of metamorphism(embryonic ores)→Thermal action of rock bodies(mesothermal metallogenic elements overlapped)→Obduction nappe, strike slip and brittle ductile shearing(initially positioning)→Extensional structure(finally positioning),closely related with brittle and ductile shear zone”; so the comprehensive metallogenic model and evolutionary pattern of gold deposit of this type have been set up 5 Obviously pointed out that major metallogenic epoch of Au in gold deposit of this type comes about only once(Sedimento metamorphic stage); the source of metallogenic metaerials is closely related to the stratigraphic unit; the absorption of peat layers and metamorphic differentiated quartz veins are the major factors, although there occurs mutliperiodic mesothermal superposition reformation of ore forming elements in later stage, yet the scope and power of its whole influence on gold is not too much; and its metallogenic type is attached to the turbidite shear zone type stratabound gold deposit in the plate tectonic obduction zone 6 Sysmatically established a suite of rapid positioning marks and effective predicted methods of gold deposits of this type; and made proposals for the prediction of gold deposits of this type that the research work should be put emphasis on 'light colored lithofacies' (made from metamorphic mineral assemblegs rather than thermal altered products) and tectonic melange accumulation, by means of the sedimentology and the dynamic mechanism of shearing, as to predict the favorable metallogenic environment and position of gold ore bodies 7 Put forward some detailed suggestions for further ore finding at different levels 8 Compiled out a set of comprehensive maps of regional geology and ore deposits which provided the overall and systematical information for the deeply studying and utilization in this area.