山东莱芜铁矿田矿体保存变化兼论地壳升降特征
Preservation Changes of Ore Bodies and the Characteristics of Crustal Rise and Fall in Laiwu Iron Field, Shandong Province

莱芜铁矿田是山东鲁西地区著名的接触交代矽卡岩型铁矿田，前人对莱芜矽卡岩型铁矿成矿规律进行了系统总结，但对莱芜铁矿田成矿后剥蚀保存的研究很少。本文运用源–运–储–变–保成矿系统论理论，以莱芜铁矿田内矿床的保存剥蚀现状为依据，研究发现莱芜铁矿田内矿体的保存及剥蚀强度较大，同时也为研究该地区地壳升降运动提供了资料支撑。研究表明：莱芜铁矿田是受早古生代碳酸盐岩地层、中生代中基性侵入岩和接触带构造三位一体控制的接触交代矽卡岩型铁矿，其形成后矿床遭受了不同程度的风化剥蚀，按照剥蚀程度不同可分为强剥蚀矿床、轻微剥蚀矿床和未剥蚀矿床，铁矿类型以原生铁矿床为主，砾岩型铁矿则占比较少。根据莱芜铁矿田内矿体形成的深度与成矿母岩的侵位深度是大体一致的客观事实，结合莱芜铁矿田成矿母岩岩石化学指数间接判断其侵入深度和剥蚀深度，依据沉积层区域厚度和钻孔揭露的残存地层厚度估算，莱芜中基性侵入岩的侵位深度应在4000~7000 m，其剥蚀深度应在3000~5000 m；铁矿体形成深度略浅于岩体侵位深度，大致在3900~5000 m范围内，而剥蚀深度基本在4000~5000 m。根据莱芜地区侵入岩和矽卡岩铁矿形成时代为130 Ma的事实，研究区内岩体侵位和矿体形成的环境演化过程大致经历了地壳持续抬升隆起阶段、强烈风化剥蚀阶段、地壳下降沉积阶段、地壳缓慢隆升期和现今的矿岩保存现状5个阶段，初步估算区内地壳的上升速率大约0.064 mm/a，而剥蚀速率大约0.033 mm/a，说明区内经历了快速隆升和较缓慢剥蚀的复杂过程，为研究区域地壳升降和区内铁矿的保存提供了佐证。
The Laiwu iron field is a famous contact metasomatic skarn iron field in the Luxi area of Shandong Province. Previous studies have systematically summarized the mineralization regularity of Laiwu skarn type iron ore, but there are few studies on the denudation and preservation after mineralization of Laiwu iron ore field. Based on the present situation of deposit preservation and denudation in the Laiwu Iron Mine Field, this paper uses the theory of sources-moving-reserviors-metamorphose- preserving metallogenic system. It is found that the preservation and denudation intensity of ore bodies in the Laiwu Iron Mine Field is relatively high, which also provides data support for the study of crustal up-and-down movement in this area. Research shows that: Laiwu iron ore field is influenced by early Paleozoic carbonate formation, basic in the Mesozoic intrusive rocks and contact zone controlled the trinity of contact metasomatic skarn type iron ore. After its formation, the deposit suffered different degrees of weathering stripping the corrosion. According to different denudation degrees, it can be divided into strong denudation deposits, slight denudation deposits and non-denudation de-posits. The main iron ore types are Proto-pig iron deposits, while the conglomerate iron ore types are relatively less. According to Laiwu iron ore field in the depth of the formation and the ore-forming mother rock ore bodies emplacement depth is generally consistent objective facts, combining with Laiwu iron ore field ore-forming parent rock geochemistry index indirectly judging its invasion depth and denudation depth. According to the regional thickness of sedimentary layers and the residual strata thickness revealed by boreholes, the emplacement depth of Laiwu intermediate basic intrusive rocks should be 4000~7000 m, and its denudation depth should be 3000~5000 m; The formation depth of iron ore body is