黔西北赫章亮岩铅锌矿床矿化—蚀变时空分带性及其找矿应用

发布时间：2018-04-26 13:49

本文选题：蚀变-岩相填图 + 蚀变-矿化分带模式　；参考：《昆明理工大学》2015年硕士论文

【摘要】：赫章亮岩Pb-Zn矿床是在川滇黔毗邻区Pb-Zn成矿带黔西北Pb-Zn矿集区内新近勘查发现的一个具有中型以上找矿潜力的富Pb-Zn矿床。矿床位于垭都-窝弓背斜南东段的垭都-蟒硐逆冲断裂上盘,已知富Pb-Zn矿体赋存在中石炭统黄龙组(C_2h)强烈白云石化的白云质灰岩及白云岩中,显示出明显的MVT型Pb-Zn矿床成矿特点。本文以区内大街矿段Ⅰ号矿体(群)为对象,在系统开展详细的立体蚀变-岩相填图和矿相学研究的基础上,借助热液矿物标型学及同位素地球化学示踪的手段,查明其蚀变-矿化特征,揭示其成矿作用过程及控制因素,建立其分带模式和成因模型,并提出找矿预测靶区。研究成果有助于深入理解川滇黔毗邻区Pb-Zn成矿带成矿流体的运移、汇聚与储存机制,并有效指导勘查找矿工作的合理部署。本次主要取得以下成果与认识:(1)系统查明了矿区的地层、构造发育特征及基本矿床地质特征。区内主干背斜为垭都-窝弓背斜,褶皱构造简单。背斜被垭都-蟒硐断裂带所破坏,背斜轴近北西向,北东翼地层出露不完整,只出露二叠纪上统龙潭组(P_31),地层倾向北东,倾角平缓,一般10°-25°。南西翼地层较为完整,核部至翼部地层以古生界为主,依次为下石炭统旧司上司组(C_1j+s)、大塘组(C_1d),中石炭统黄龙组(C_2h)、马平组(C_3m),下二叠统梁山组(P_1l)、栖霞-茅口组(P_1q+m),中二叠统峨眉山组(P_2e),上二叠统龙潭组(P_31)。地层倾向南西,倾角较陡,30°-45°之间。次为轿顶山向斜,向斜轴近北东向,出露地层为下石炭统大塘组(C_1d),中石炭统黄龙组(C_2h)、马平组(C_3m),下二叠统梁山组(P_1l)、栖霞组(P_1q),地层倾向15°-35°之间。区内主干断裂F_1走向北西,倾向南西,倾角45°-60°,为一逆断层,切割深度大,断距超过1km;次为F4走向北西,倾向南西,倾角16°-30°,为一逆断层;F_1及F4同属于垭都-蟒硐断裂带的分支断裂,矿区内主要表现为F_1及F4叠瓦状推覆使垭都-窝弓背斜及轿顶山向斜复合部位是该区铅锌矿富集的最有利部位;区内已知铅锌矿体集中分布于区域性断裂的次级断层及伴生裂隙带中,多呈似层状、透镜状顺层产出。其中,Ⅱ号矿体产于F_1断层上盘的下石炭统大塘组粗晶白云岩及黄龙组细-中晶白云岩中,走向NNW向,由呈囊状、透镜状与地层有小角度相交主矿体及旁侧囊状分支矿体组成,主矿体在垂向上发生扭曲,上部倾向SE,下部倾向SW,倾角44°～71°之间;主矿体控制斜深大于150m,一般厚2～6m,均厚3m,品位较富,且Zn高Pb低,一般Pb2%～10%,Zn4%～30%。Ⅰ号矿体呈似层状产于F_1断裂上盘的上石炭统黄龙组白云质灰岩中,倾向NE,倾角54°～57°。主矿体控制长80～100m,倾向延伸60m,厚1.2～1.4m,均厚1.3m。矿石品位一般Pb 2%～3%、Zn 3%～7%。矿石矿物组合为闪锌矿(Sp)[本文的矿物缩写符号参考沈其韩(2009)][28]、铁闪锌矿(Fe-Sp)、方铅矿(Gn)、黄铁矿(Py)及少量白铁矿(Mrc)、黄铜矿(Cpy)等;脉石矿物组合为方解石(Cal)、铁方解石(Fe-Cal)、白云石(Dol)及少量石英(Q)、菱铁矿(Sd)、沥青(Org)等。围岩蚀变主要为黄铁矿化、白云石化、方解石化、铁锰碳酸盐化及硅化,其中白云石化、黄铁矿化与铅锌矿化关系密切。热液成矿作用可分为(Ⅰ)Dol(-Py)阶段、(Ⅱ)Dol-Sp(红色)-Gn-Py(-Q)-Cal阶段、(Ⅲ)Dol-Py-Sp(褐色)-Gn-Cal(-Q)阶段、(Ⅳ)Dol-Py-Sp(棕褐色)-Gn-Cal(-Q)阶段及(Ⅴ)Cal阶段等5个矿化阶段,其中Ⅱ、Ⅲ阶段是主要的矿化时期。(2)查明大街矿段Ⅰ号矿体(群)的矿化-蚀变空间分带型特征,即:从矿体中心向外、自上而下,蚀变表现为方解石化→白云石化→硅化→绿泥石化;矿化表现为致密块状、角砾状Pb-Zn矿石→致密块状Py壳→脉状、浸染状、斑点状Pb-Zn矿石→脉状、星点状Py壳的分带特点;相应的矿物组合为Sp+ Gn+ Py+Apy+ Cal+ Q+ Ill 组合→Py+ Gn+ Sp+ Dol+ Cal+ Fe-Cal 组合→Py+ Dol+ Cal 组合→Py+Q+Chl+Cal组合;总体上看,其横向分带性较为显著,而纵向分带型不明显,这与成矿热液的浓度梯度、横向渗透扩散受岩性垂向物性变化影的响密切有关;铅锌成矿作用贯穿于5个阶段成矿作用的全过程,红色Sp+Py是早阶段流体的产物,角砾状矿石是流体叠加的产物,Ⅲ、Ⅳ阶段形成的褐色Sp的流体温度较Ⅰ阶段红色Sp要高,且1750m高程为流体叠加的前锋。显然,该矿床与区域铅锌成矿带上如毛坪等大型铅锌矿床的蚀变-矿化分带特点与机制有所不同。(3)总结了不同矿化-蚀变带内白云石、黄铁矿及闪锌矿等热液矿物的标型学特征,建立其矿化-蚀变分带模式。其中,空间上:白云石从矿体中心向外围为块状粗晶→块状、脉状细晶,Py由{210}、五角十二面体及其聚形→{100}、立方体及其聚形,时间上:白云石由粗晶→细晶,黄铁矿由五角十二面体居多→立方体居多,闪锌矿早期以红色为主,晚期以褐色为主;反应矿床为中低温热液矿床且从早阶段到晚阶段成矿温度先升高后降低的趋势。(4)查明了成矿物质来源及成矿流体的演化特征。矿区热液矿物的C、O、S及Pb同位素地球化学示踪研究结果表明,成矿流体及物质具有多源特点,硫可能早期为细菌还原作用形成,随着成矿流体温度逐渐升高,成矿流体的S则主要由海相硫酸盐热还原作用形成,在还原过程中,下伏页岩、碎屑岩和泥质岩地层中的有机质发挥了→定的作用。矿床中围岩的CO_2可能与峨眉山玄武岩浆提供的热动力有关,而热液方解石的CO_2早阶段可能有低温蚀变作用形成,随着成矿温度升高,后期则主要为海相碳酸盐岩提供。这与闪锌矿标型特征研究显示早期为低温,后期温度逐渐升高再降低相吻合。成矿金属来源于上地壳(与区域D-P不同时代碳酸盐岩地层及基底岩石铅同位素组成相近,明显不同于峨眉山及震旦系灯影组铅同位素组成),具有多源性特点。(5)总结厘定了区内Pb-Zn矿床的成矿作用过程,建立了其成因模型。即:早期由于区域挤压应力作用地层强烈褶皱,形成断裂及裂隙,下渗的地表水及地下水在重力及浓度驱动下沿断裂及裂隙经过含沉积型Pb、Zn等金属元素的地层时萃取地层的金属元素形成含矿热卤水,经过有利的碳酸盐地层时含矿热卤水沿断裂及裂隙蚀变围岩形成白云石化同时溶蚀围岩形成溶洞、孔洞等,含矿热卤水沿溶洞、晶间孔隙及断层破碎带等有利空间富集沉淀,随着流体的迁移演化形成从矿体中心向外围形成方解石化→白云石化→方解石化的蚀变空间分带及致密块状矿石→脉状、斑块状矿石的矿石分带,后期断层活化形成角砾状矿石,致使矿体中心形成角砾状矿石的分带。从而形成流体贯入-地层萃取-构造控矿的机制。(6)结合矿区实际地质条件和前述认识,提出了3个隐伏矿找矿预测靶区。其中,大街矿段预测靶区经工程验证,已新增探获Pb-Zn资源金属储量5万吨,品位Pb 2%～10%,Zn 4%～30%。目前,亮岩矿区Pb-Zn资源金属储量已累计超过10万吨,仍具有较好的找矿潜力。
[Abstract]:The Hezhang bright rock Pb-Zn deposit is a rich Pb-Zn deposit, which has the potential of medium and above the prospecting in the Pb-Zn ore area of the northwest of Guizhou Province, the Pb-Zn metallogenic belt of the adjacent area of the Sichuan Yunnan Guizhou Province. The deposit is located in the upper reaches of the Shadu adit thrusting fault in the South East of the guadu anticline anticline. The rich Pb-Zn orebody is known to be strong in the Middle Carboniferous Huanglong group (C_2h). Dolomitization and dolomitization of dolomitic limestone and dolomite show obvious metallogenic characteristics of the MVT type Pb-Zn deposit. This paper, based on the detailed three-dimensional alteration - lithofacies mapping and mineralogical study, is based on the detailed three-dimensional alteration - lithofacies mapping and mineralogical study. The ore-forming process and controlling factors are revealed, its zoning model and genetic model are established, and the prospecting target area is put forward. The research results are helpful to understand the migration, accumulation and storage mechanism of the ore-forming fluid in the Pb-Zn metallogenic belt in the adjacent area of Sichuan, Yunnan and Guizhou Province, and to guide the rational deployment of prospecting and prospecting work. The main achievements and understanding are as follows: (1) the strata of the mining area, the characteristics of tectonic development and the geological characteristics of the basic ore deposits have been ascertained systematically. The main trunk anticline in the area is the Yu - U - Du - bow anticline, and the fold structure is simple. The anticline is destroyed by the Yu Du Python fault zone, the anticline axis is near to the North West, the north east wing is not fully exposed, and the Permian upper Longtan is exposed only. Group (P_31), the formation tendency is North East, the dip angle is gentle, 10 degree -25 degree. The South West Wing is more complete, the core to the wing part is the Paleozoic, which is the lower Carboniferous old division superior group (C_1j+s), the Datang Group (C_1d), the Middle Carboniferous Huanglong group (C_2h), the Ma Ping group (C_3m), the lower two Liangshan formation (P_1l), the Qixia Makou group (P_1q+m) and the middle two stack. The Meishan formation (P_2e) and the upper two series Longtan Formation (P_31). The strata tend to be southwestern, with steep dip and 30 degree -45 degrees. The second is the sedan roof syncline, the syncline axis is near to the North East, the outcropping is the lower Carboniferous Dang Tong Group (C_1d), the Middle Carboniferous Huanglong Formation (C_2h), the Ma Ping group (C_3m), the lower two series (P_1l), the Qixia group (P_1q), and the formation tendency 15 degree -35 degrees. The internal main fault F_1 tends to NW and tends to South West, with a dip angle of 45 -60 degrees, which is a reverse fault, with a large cutting depth and more than 1km; the second is F4 toward the North West, and tends to South West, the dip angle is an inverse fault, and F_1 and F4 belong to the branch fracture of the Ya Du Python fault zone, and the main manifestation is F_1 and F4 stacking like nappe in the ore area. And the compound part of the sedan mountain syncline is the most favorable part of the enrichment of the lead-zinc deposits in this area, and the lead and zinc ore bodies are known to be concentrated in the secondary faults and associated fracture zones of the regional faults, which are mostly like layered and lenticular formation, and the No. 2 orebodies are produced in the lower Carboniferous Dang formation of the F_1 fault and the fine dolomite and Huanglong Formation in the lower Carboniferous Formation. In MICROTEK dolomite, it moves towards NNW direction, which is composed of main ore body and side sac branch orebody, which is cystic and lens with small angle of formation. The main ore body is twisted vertically, the upper part tends SE, the lower part tends SW and the dip angle is 44 to 71 degrees; the main ore body controls the slanting depth more than 150m, the thickness is 2 to 6m, the thickness is 3M, the grade is rich, and Zn Pb is low. The Pb2% ~ 10%, Zn4% ~ 30%. I orebodies appear in the upper Carboniferous Huanglong dolomitic limestone, which resembles the upper Carboniferous Huanglong Formation of the F_1 fracture plate, which is inclined to NE and the dip angle is from 54 to 57 degrees. The main ore body is controlled by 80 to 100m, which tends to extend 60m, thick 1.2 to 1.4m, and the grade of 1.3m. ore is generally Pb 2% to 3%, Zn 3% ~ 7%. ore mineral assemblage is sphalerite (mineral mineral). Abbreviations refer to Shenyang (2009)][28], iron sphalerite (Fe-Sp), galena (Gn), pyrite (Py) and a small amount of pyrite (Mrc) and chalcopyrite (Cpy); the gangue mineral assemblage is calcite (Cal), iron calcite (Fe-Cal), dolomite (Dol) and less Liang Shiying (Q), siderite (Sd), asphalt (Org), etc.. The alteration of surrounding rock is mainly pyrite mineralization, dolomitization, and square The mineralization of dolomitization and pyrite mineralization are closely related to lead-zinc mineralization. The hydrothermal mineralization can be divided into (I) Dol (-Py) phase, (II) Dol-Sp (red) -Gn-Py (-Q) -Cal stage, (III) Dol-Py-Sp (brown) -Gn-Cal (-Q) stage, (IV) Dol-Py-Sp (brown) -Gn-Cal (-Q) stage and (V) stage of mineralization. The stage II and III stage is the main mineralization period. (2) to find out the mineralization and alteration spatial zoning characteristics of No.1 ore body (Group) of the main street ore section, that is, from the center of the ore body outward, from the top to bottom, and the alteration is shown as calcification, dolomitization, silicification and green mud petrifaction, and the mineralization is dense and massive, breccia Pb-Zn ore to dense massive Py shell. The characteristics of the zonation of pulse, dipping, spotted Pb-Zn ore, pulse and star shaped Py shell; the corresponding mineral assemblages are Sp+ Gn+ Py+Apy+ Cal+ Q+ Ill combination, Py+ Gn+ Sp+ Dol+ assemblage of Sp+ Dol+. The concentration gradient of the metallogenic hydrothermal fluid is closely related to the effect of the lithologic vertical physical change, and the lead and zinc mineralization runs through the whole process of the 5 stages of mineralization. The red Sp+Py is the product of the early stage fluid, the breccia ore is the product of the superposition of the fluid, and the temperature of the brown Sp formed in stage III and IV is more red than the stage I red. Sp is high, and the 1750m elevation is a fluid superposition forward. Obviously, the alteration and mineralized zoning characteristics of the deposit and the regional lead zinc metallogenic belt, such as Mao Ping and other large lead-zinc deposits are different. (3) the typomorphic characteristics of the hydrothermal minerals, such as dolomite, pyrite and Sphalerite in different mineralization and alteration zones, are summarized, and their mineralization and alteration points are established. With the pattern, in space, the dolomite from the center of the ore body to the periphery is lumpy coarse grain, massive and fine grain, Py from {210}, five horns and twelve sides and their aggregation to {100}, cubes and their aggregation. The period is mainly brown, the reaction deposit is a medium low temperature hydrothermal ore deposit and the mineralization temperature of the metallogenic material rises first and then decreases. (4) the origin of the metallogenic material and the evolution characteristics of the ore-forming fluid are found out. The geochemical tracing results of C, O, S and Pb isotopes of hydrothermal minerals show that the ore-forming fluids and materials are characterized by multi source characteristics. Sulfur may be formed in the early stage of bacterial reduction. As the temperature of the ore-forming fluid rises gradually, the S of the ore-forming fluid is mainly formed by marine sulphate thermal reduction. In the process of reduction, the organic matter in the underlying shale, clastic rock and argillaceous rock stratum has been determined to be used. The CO_2 of the surrounding rock in the deposit may be with the basalt magma of the Mount Emei. The thermal dynamics are provided, and the CO_2 early stage of the hydrothermal calcite may be formed by low temperature alteration. With the increase of the metallogenic temperature, the later phase is mainly provided by marine carbonate rocks. D-P the lead isotope composition of carbonate rocks and basement rocks in different times is similar, obviously different from the lead isotopic composition of the Mount Emei and the Sinian Dengying group. (5) the metallogenic process of the Pb-Zn deposits in the region was determined and its genetic model was established. Fracture and fracture are formed. The surface water and groundwater under infiltration are driven by gravity and concentration, and the metallic elements of the metal elements such as Pb, Zn and other metallic elements are extracted from the fractured and fractured formations to form the ore bearing hot brine in the formation. At the time of dissolution, the surrounding rock formed karst cave, hole and so on. The ore bearing hot brine was enriched and precipitated along the karst cave, intergranular pore and fault fracture zone. With the migration and evolution of the fluid, the altered space zoning from the center of the ore body to the periphery of the ore body was formed, and the ore of the dense massive ore to the vein and the plaque like ore was formed. Stone zoning and later fault activation to form breccia ore, resulting in the formation of breccia ore in the center of the ore body, forming a mechanism of fluid penetration - formation extraction - structural ore control. (6) combining the actual geological conditions of the mining area and the foregoing understanding, the prospecting target area of 3 concealed ore deposits has been put forward. The newly discovered metal reserves of Pb-Zn resources are 50 thousand tons, the grade Pb 2% ~ 10%, Zn 4% ~ 30%., the metal reserves of Pb-Zn resources in the bright rock mining area have accumulated more than 100 thousand tons, and still have good prospecting potential.

【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.4

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