云南澜沧老厂多金属矿区构造及其控矿研究

【作者】 杨帆；

【导师】 李峰；

【作者基本信息】 昆明理工大学 ， 构造地质， 2011， 硕士

【摘要】 澜沧老厂矿区是三江成矿带南段重要的多金属成矿区之一,最新研究表明澜沧老厂在成因上属于火山喷流沉积叠加隐伏斑岩热液成因为主的多因复成矿床。本文在充分收集前人资料和多次实际调研的基础上,侧重研究矿区及区域构造特征、构造演化及其与火山喷流沉积成矿系统和隐伏花岗斑岩成矿系统的关系,总结构造及其对成矿系统的控制。晚古生代以来,澜沧地区区域动力学环境多次转变,区域构造演变过程可分为裂谷期(D-P1)→裂谷封闭-隆升期(P2-K)→陆内碰撞造山期(新生代以来)三大构造期。受区域大地构造体制演变-转化的影响,老厂多金属矿床的成矿演化复杂而特殊：在时间上随大陆裂谷→陆内碰撞造山带的形成与演化,依次出现早石炭世火山喷流沉积成矿作用占主导→喜山期斑岩成矿作用占主导的成矿作用演变过程,形成特有的“双成矿系统”。研究区褶皱除矿区本部的老厂背斜和睡狮山向斜外,本部以东还有上云山背斜。其中老厂背斜形态复杂,是重要控矿构造。矿区断裂构造发育,包括SN向、NW向的主干断层以及NE向和EW向的次要断层。SN向和NW向断层应是矿区形成最早的构造,演化历史长,断层多期活动明显,性质多次转化,至少经历张性→挤压→右行走滑为主的多次活动过程,具继承性活动特征。矿区内NE向、EW向断层规模较小,对岩性岩相的控制不明显,可能形成于裂谷封闭期后。构造对火山喷流沉积成矿系统的控制,主要体现在裂谷对成矿的控制和断裂褶皱对矿体的控制与改造两方面。澜沧裂谷基底富铅锌银,裂谷边界及主干断裂是穿透性构造,不仅是岩浆上升-喷发的通道,还是深部成矿流体上涌-聚集的有利构造；裂谷中的地堑式多级盆地为成矿提供了良好的沉积洼地,利于成矿物质沿同生断裂带聚集与沉积成矿；裂谷封闭过程中,断裂构造性质反转,地层普遍褶皱,火山喷流沉积型矿体(Ⅰ、Ⅱ、Ⅴ号矿体群)呈叠瓦状抬升,与地层同步变形,并可在次级褶皱转折端加厚富集；陆内碰撞造山期的强烈构造挤压与区域性抬升,使火山喷流沉积型矿体进一步变形改造,局部隆升剥蚀。构造对斑岩成矿系统的控制,主要体现在对隐伏斑岩体空间分布的控制及斑岩有关的矿体群(Ⅲ、Ⅳ、Ⅵ号矿体群)的控制。据岩体产出特征分析,隐伏花岗斑岩体总体受老厂背斜及F1、F4断层联合控制,背斜轴部两断层交汇处为斑岩体高侵位地段；沿岩体突起顶部及其裂隙带,形成披覆状厚大细脉-浸染状钼(铜)矿体群(Ⅵ号矿体群)；具继承性活动的F1、F3和F1l等南北向主干断层控制了热液充填型大脉状铅锌银矿体群(Ⅳ号矿体群)的产出；主干断层旁侧的次级断层及节理裂隙带中,不仅普遍发生低温热液蚀变,还形成大量不规则脉状-透镜状铅锌银矿体群(Ⅲ号矿体群)；更多还原

【Abstract】 Lancang lead deposit is one of important polymetallic deposits in south segment of Tri-rivers region in Yunnan province, China. The recent researches indicate that the genesises of Landcang ore deposit are compounded with Carboniferous volcano exhalative sedimentary and Himalayan concealed granite porphyry heated liquid. Based on the data collection and field survey, the regional tectonic features and tectonic evolvement and the relations to the systems of volcano exhalative sedimentary metallogenic and concealed granite porphyry metallogenic have been studied. Especially, the metallogenic system controlled by tectonic has been studied in detail.Since the late Paleozoic, the regional dynamic conditions have been changed in times. The evolution process of regional tectonic can be divided into 3 phases which are period of rift (D-P1), rift-close and lift (P2-K) and continental collision. Controlled by the complex tectonic conditions, the evolution process of the poly-metallogenic of Lancang ore deposit is also very complex. The in time sequence, when the tectonic was from rift to continental collision, the double metallogenic systems which processed from Carboniferous volcano exhalative sedimentary to Himalayan concealed granite porphyry heated liquid had been formed.In the research field, there are three folds including Shangyunshan anticline and Laochang anticline and Shuishishan syncline. The conformation of Laochang anticline is very complex and also an important ore-controlling structure. The faults are mainly spread in SN and NW directions and in NE and EW directions. The evolution process of the faults is very long and the activities of the faults can be observed in many stages which are at less including tension and squeeze and dextral strike slip. The faults in NE and EW directions are relative small.The Carboniferous volcano exhalative sedimentary controlled by tectonic in two aspects:the rift controls the metallogenic, the faults and the folds control the ore body. The boundary of the rift and the main fault are transfixion tectonics which is not only the channels for the magma ascending and eruption but also the space for the collection of rising metallogenic flow. The rift valley multi-stage basin in the rift is a good sedimentary depression for metallogenic and also helpful in the accumulation and sedimentary of minerals along the fault belt. During the process of rift close, the properties of faults reversed and many folds happened and the ore bodies lifted imbricately in phase of the deformation of stratum and can be enriched at the transition part of the folds. The continental collision of tectonic compression and strong regional uplift make the volcanic exhalation-sedimentary ore body deformed more.The porphyry metallogenic system is controlled by tectonic in two parts which are the space shape of concealed porphyry body and the ore body group related to the porphyry. According to the characters of the rock characteristics of occurrence, the concealed porphyry granite is controlled by Laochang anticline and faults F1 and F4. the shaft of the anticline locates the intersection of the two faults for the high intrusion of porphyry. Along the top the salience of porphyry and the rift belt, veins disseminated molybdenum(copper) ore body group has been formed. The nervation heated liquid filling ore body (IV orebody group) of Pb-Zn-Ag has been controlled by the main faults in NS direction such as F1 and F3 and F11and etc. In the secondary faults and fissures and cracks, there is not only low temperature heated liquid alteration but also many Pb-Zn-Ag ore body group(III orebody group) shaped in irregular nervation and lenticular.更多还原