雪峰造山带南段靖州盆地成因性质及形成背景
Nature, origin and tectonic setting of Jinzhou basin in the south segment of Xuefeng orogen
-
摘要: 提要：靖州盆地是位于雪峰构造带南段的一个NE向晚三叠世—中侏罗世小型陆相盆地，前人研究提出其为NNE向溆浦—靖州大断裂左行走滑形成的拉分伸展盆地。本文对靖州盆地构造特征、T3—J2沉积和原型盆地特征等进行了系统研究，在此基础上提出该盆地实为挤压类前陆盆地，主要依据有：①沉积物高成熟度以及残留盆地边界与盆地周缘先期地质界线总体协调一致，说明盆地沉积时为挤压挠曲作用下形成的低缓洼地；②沉积物高成熟度和远源特征，指示盆地形成于相对稳定构造环境；③盆地北端T3—J1沉积空间由岩层弯曲下凹提供；沉积物产状变化指示J2盆地受到NW向挤压并产生持续褶皱变形；沉积物特征指示沉积环境西浅东深，进一步暗示J2盆地发展受控于NW向挤压与东缘逆冲块体的重力载荷；④盆缘伸展断裂少见，因挤压形成的小型走滑断裂、逆断裂、共轭剪节理等则多见；⑤从溆浦—靖州断裂走向偏转情况来看，该断裂左行走滑时靖州盆地所处部位应为挤压区而非拉张区。据盆地沉积和构造特征及区域大地构造演化背景，盆地的形成主要与晚三叠世—早侏罗世区域SN向挤压、中侏罗世区域NWW向挤压和NNE向左行走滑有关。Abstract: Abstract：Jinzhou basin is a small NE-trending Late Triassic-Middle Jurassic continental basin in the south segment of Xuefeng orogen. Previous researchers held that the basin is a pull-apart extensional basin related to dextral strike-slipping of NNE-trending Xupu-Jinzhou fault. The authors studied the tectonic characteristics, sedimentary features and proto-basin of Late Triassic-Middle Jurassic Jinzhou basin and, on such a basis, brought forward the opinion that the basin is a compressional quasi-foreland basin according to evidence as follows： ① High maturity of the deposits and the harmony of the basin boundary with surrounding older geological boundary indicates that the basin is a compressional low depression. ② High component maturity and far-resource features of the deposits suggest that the basin was formed in a stable tectonic setting. ③ The sedimentary space of Upper Triassic-Lower Jurassic strata in the northern basin was formed from rocks bending. The attitude changes of rocks indicate that the basin was NW-compressed and folded in Middle Jurassic. Sedimentary features show that there existed shallow- and deep-water environment in the west and the east of the basin, respectively, which implies that the basin was controlled by gravity load of east peripheral thrust block. ④ In adjacent areas of the basin, there occur a few extensional faults and a lot of small strike-slip faults, thrust faults and conjugated shear joints related to the compression. ⑤ According to the strike deflexion of the fault, Jinzhou basin was situated in a compressional area instead of an extensional area when Xupu-Jinzhou fault experienced dextral strike-slipping action. Based on the sedimentary and tectonic characteristics of Jinzhou basin and the regional tectonic setting, the authors hold that the basin was related mainly to regional S-N-compression during Late Triassic-Early Jurassic period, and related to NWW-compression and NNE-trending dextral strike-slipping during Middle Jurassic period.
-
Keywords:
- quasi-foreland basin /
- compression /
- strike-slip /
- Late Triassic-Middle Jurassic /
- Jinzhou basin
-
1. 研究目的（Objective）
碳酸钙是全球应用最广泛的非金属矿物材料之一，它不仅是建材、造纸、塑料、涂料、橡胶、油漆、冶金等行业的原料或改性功能材料，而且在日用化工、食品、医药、卫生保健等领域发挥着独特的作用。广西贺州大理岩矿产丰富，被誉为全国“重钙之都”，但石灰岩矿（轻质碳酸钙）勘查程度低，为了加快传统产业转型升级和新经济新业态转化培育，贺州市以粤港澳大湾区市场需求为引领，将重质碳酸钙领域拓展到轻质碳酸钙、氧化钙和氢氧化钙领域，构建绿色高端碳酸钙千亿元产业集群，本次在贺州市水声肚地区开展了石灰岩矿的勘查研究工作。
2. 研究方法（Methods）
通过开展详查工作，采用大比例尺地质填图圈定含矿层位；采用勘查线的布置形式，地表施工槽探、深部系统施工钻探揭露控制，最终通过全孔采样分析，圈定有色冶金熔剂用石灰岩矿体，估算资源量，实现了快速找矿突破。同时研究分析了水声肚矿区石灰岩矿体的主要赋矿层位，矿体规模、形态、产状、厚度、品位，矿石结构构造、矿物成分、化学成分、矿石类型，确定找矿标志。
3. 结果（Results）
通过项目实施，水声肚矿区熔剂用石灰岩矿的主要含矿层位为融县组下段（D3r1）和桂林组上段（D3g3）（图 1a）。融县组下段岩性为浅灰色-灰白色中厚层亮晶微晶粒屑灰岩夹纹层状含生物屑微晶灰岩，厚50~60 m；桂林组上段岩性为深灰色生物碎屑灰岩夹多层层孔虫灰岩，厚67~131 m。
![]()
图 1 水声肚矿区地质简图（a）、层孔虫灰岩矿石和镜下照片（b）及1号勘查线剖面图（c）Figure 1. Simplified geological map of the Shuishengdu area (a), microscopic photos of stromatoporoid limestone ore (b) and section of No.1 exploration line (c) in the Shuishengdu area通过系统工程控制和采样分析，圈出了①号熔剂用石灰岩主矿体，矿体走向延长约2350 m，倾向延长约1650 m，水平投影面积约2.05 km2。矿体剖面形态呈单斜厚大层状、板状（图 1b）。矿体平均倾向193°，平均倾角21°。通过45个钻孔施工，控制矿体厚度11.01~179.53 m，平均99.02 m。单工程品位：CaO 53.75%~54.84%，平均54.44%；MgO 0.52%~1.17%，平均0.75%；SiO2 0.20%~1.33%，平均0.48%。
矿石结构以生物碎屑（含层孔虫、腕足类）泥晶结构（图 1c）、微晶结构为主，构造主要为块状构造。矿石矿物成分主要为方解石（约98%），含少量的泥质（约2%）。据组合分析结果：Al2O3平均含量0.24%；Fe2O3平均含量0.08%；S平均含量0.022%；P平均含量0.0019%；烧失量平均43.57%。表明矿区熔剂用石灰岩有害组分含量极低。矿石工业类型为有色冶金熔剂用石灰岩，均达一级品，部分达特级品。
4. 结论（Conclusions）
(1) 本次勘查在水声肚矿区新发现超大型有色冶金熔剂用石灰岩矿床，共估算石灰岩矿石资源量（控制+推断）为72956.46万t，矿区北部直接出露地表的石灰岩矿石量超2亿t，为贺州市碳酸钙产业转型升级提供资源保障，也为贺州市创建“广西东融先行示范区”迈开了加速步伐。
(2) 确定水声肚地区有色冶金熔剂用石灰岩矿的主要赋矿层位为融县组下段和桂林组上段。
5. 致谢（Acknowledgements）
项目实施过程中得到了广西贺州市自然资源局的大力支持，谨此表示感谢。
下载:
计量
- 文章访问数: 3026
- HTML全文浏览量: 63
- PDF下载量: 3761
