| 西南天山中新生代盆地成矿流体运移规律 |
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| 引用本文： | 贾润幸,方维萱.西南天山中新生代盆地成矿流体运移规律[J].地质力学学报,2021,27(4):529-541. |
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| 作者姓名： | 贾润幸 方维萱 |
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| 作者单位： | 有色金属矿产地质调查中心, 北京100012;有色金属矿产地质调查中心矿山生态环境资源创新实验室, 北京100012 |
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| 基金项目： | 中国地质调查局项目（121201004000150017-47，121201004000160901-67）；国土资源部公益性行业科研专项项目（201511016） |
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| 摘 要： | 乌拉根铅锌矿床和萨热克铜矿床是西南天山中新生代盆地最有代表性的两个层控砂砾岩型矿床，乌拉根铅锌矿床产于下白垩统克孜勒苏群第五岩性段(K1kz5)的粗砂质细砾岩中，后期经历了弱的构造改造作用；萨热克铜矿床产于上侏罗统库孜贡苏组上段(J3k2)杂砾岩中，其北矿段后期经历了强烈的构造改造作用，南矿段可见岩浆热液蚀变作用后的褪色化及叠加成矿作用。为了研究成矿流体和岩浆热液在岩石中的运移规律，分别对上述两个矿区以沉积作用、构造改造作用和岩浆作用为主的代表性岩石测定了孔隙度和渗透率。测试结果表明乌拉根矿区岩(矿)石的孔隙度和渗透率总体比萨热克矿区岩石的孔隙度和渗透率要小；乌拉根铅锌矿区和萨热克铜矿区北矿段矿石的孔隙度和渗透率均小于下盘围岩的孔隙度和渗透率；萨热克铜矿区南矿段经历了岩浆热液蚀变，岩石的孔隙度和渗透率明显小于未受岩浆作用的岩石孔隙度和渗透率，且辉绿岩脉下盘岩石的孔隙度和渗透率明显小于上盘。同时通过岩(矿)石组构分析，上述岩(矿)石在成岩和成矿后孔隙度和渗透率的变化均与成矿流体或岩浆热液的作用密切相关。在西南天山中新生代层控型矿床中，当成矿流体沿切层断裂上升后会优先选择孔隙度和渗透率高的岩层进行渗滤、扩散、充填和交代作用。岩石中的砾石砾径越大，砾石间隙越大；岩石的硬度越大，其在后期构造变形中越容易形成构造裂隙，对成矿越有利，这也是造成萨热克铜矿北矿带中的金属硫化物颗粒明显大于乌拉根铅锌矿中金属硫化物的重要原因。上述结果表明沉积盆地中成矿流体或岩浆热液的成矿作用越强，岩石受其影响在成岩成矿后的孔隙度和渗透率越会变小，从岩石的孔隙度和渗透率可间接反映成矿过程中成矿作用的强弱，为寻找富矿体提供理论依据。
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| 关 键 词： | 中新生代沉积盆地 孔隙度和渗透率 盆地构造变形 成矿流体 西南天山 |
| 收稿时间： | 2020/11/9 0:00:00 |
| 修稿时间： | 2021/5/10 0:00:00 |
The migration rule of the ore-forming fluids in the Meso-Cenozoic Basins, Southwestern Tianshan, China |
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| JIA Runxing,FANG Weixuan.The migration rule of the ore-forming fluids in the Meso-Cenozoic Basins, Southwestern Tianshan, China[J].Journal of Geomechanics,2021,27(4):529-541. |
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| Authors: | JIA Runxing FANG Weixuan |
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| Institution: | 1.China Non-ferrous Metals Resource Geological Survey, Beijing 100012, China2.Innovation Laboratory of Mine, Environment and Mineral, China Non-ferrous Metals Resource Geological Survey, Beijing 100012, China |
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| Abstract: | The Wulagen pb-zn deposit and the Sareke copper deposit, two most representative strata-bound glutenite deposits in the Meso-Cenozoic Basins in Southwestern Tianshan, are the subjects of our study. The Wulagen pb-zn deposit occurred in the coarse sandy fine conglomerates in the Section 5 of the Lower Cretaceous Kizilsu group(K1kz5) and have underwent weak tectonic reworking in the late period; The Sareke copper deposit occurred in anagenites in the upper section of Upper Jurassic Kuzigongsu formation (J3k2), and the northern part shows obvious tectonic reworking and enrichment mineralization, while the southern part shows discoloration and superposition mineralization after magmatic hydrothermal alteration. In order to study the migration law of ore-forming fluids and magmatic hydrothermal fluids in rocks, the porosity and permeability of the representative rocks dominated by sedimentation, tectonic reworking and magmatic hydrothermal alteration in the two mining areas were measured respectively. The test results show that the rocks in the Wulagen deposit area generally have low porosity and permeability than those in the Sareke deposit; the rocks in the Wulagen lead-zinc deposit and the northern part of the Sareke copper deposit have low porosity and permeability than their footwall rocks; the porosity and permeability of the rocks subjected to magmatic hydrothermal alteration in the southern part of the Sareke copper deposit are obviously lower than those not subjected to magmatic alteration, and the porosity and permeability of the footwall rocks of diabase dike are significantly lower than those of the upper rocks. According to the analysis of rock (ore) fabric, the changes of porosity and permeability after diagenesis and mineralization are closely related to the action of ore-forming fluids or magmatic hydrothermal fluids. In the Meso-Cenozoic strata-bound deposits in the southwestern Tianshan Mountains, rock strata with high porosity and permeability are preferred to be permeated, diffused, filled and metasomatized when ore-forming fluids rise along the cutting layer faults. The larger the gravel diameter is in the rock, the larger the gravel gap is; the greater the hardness of the rock, the easier it is to form structural cracks in the later tectonic deformation, and the more favorable it is for mineralization. This is also the important reason that the metal sulfide particles in the northern part of the Sareke copper deposit are obviously larger than those in the Wulagen lead-zinc deposit. In the process of magma intrusion, the alteration of the footwall quartz sandstone by the magmatic hydrothermal fluids is stronger than that of the hanging wall. The above results indicate that the stronger the mineralization of ore-forming fluids or magmatic hydrothermal fluids are in sedimentary basins, the lower the porosity and permeability of affected rocks will be after diagenesis and mineralization. The porosity and permeability of rocks can indirectly reflect the strength of mineralization and provides a theoretical basis for searching for ore shoots. |
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| Keywords: | Meso-Cenozoic Basin voidage and permeability tectonic deformation of basin ore-forming fluid Southwestern Tianshan |
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