兴蒙造山带及华北板块北缘钼矿化——进展、规律、问题与成因初探

发布时间：2018-03-04 16:00

本文选题：地质学　切入点：斑岩钼矿床　出处：《矿床地质》2017年03期 　论文类型：期刊论文

【摘要】：兴蒙造山带及其南侧受古亚洲洋南向俯冲所影响的华北板块北缘内各有1条显著的中生代斑岩钼成矿带,并在东西两侧首尾相连。文章综述了伸展环境下的斑岩钼矿床的研究进展,对兴蒙造山带及华北板块北缘内这2条钼成矿带的成矿背景、分布规律、矿床共生组合特点、成矿岩浆的属性、巨量金属和水的来源以及斑岩铜、钼矿化的异同等进行了总结,并从成矿岩浆源区塑造过程的角度初步探讨了巨型钼成矿带的形成特点。这2条钼成矿带在地质特征和区域矿床组合上非常相似,具有相似的启动时间和峰值时间,与区域内的斑岩铜矿化在时代上具有不共生的特点,矿化特征也与美国科罗拉多地区产出的高F型斑岩钼化类似,二者构成了统一的整体。元素地球化学对比研究显示,南、北2条钼成矿带的成矿岩浆与古生代斑岩铜成矿岩浆以及中生代的碱性岩浆均具有相似的特征,为脱水熔融的产物,并与古老陆下岩石圈地幔包体、新生代软流圈地幔玄武岩具有显著的差别。研究认为,南钼矿带的岩浆源区是亏损金属和水的古老岩浆源区在古生代洋片俯冲过程脱水交代改造后的产物,北钼矿带的岩浆源区是古生代洋片俯冲增生形成的富水源区。成(含)矿岩石Sr同位素研究显示,南、北2条钼成矿带成矿源区均启动于Rb/Sr比值较低的源区,受到上部高Rb/Sr比值地壳的混染;Nd同位素特征的对比研究显示,二者初始Nd值差别极大,但是Sm/Nd比值非常相似,显示放射性成因Nd的积累在三叠纪以后是一致的,也说明初始Nd值的差别是成矿源区塑造前所形成和继承的,同时也说明初始Nd值的差异可能掩盖了Mo成矿岩浆形成的真正原因。通过与世界范围内其他典型钼成矿带的对比研究,认为南、北2条钼成矿带成矿的岩浆源区位于陆下岩石圈地幔,古生代期间古亚洲洋向南、北两侧的俯冲在其形成过程中具有重要作用,主要体现在塑造富集型源区、水化造山带和增厚岩石圈等几个方面。俯冲改造、加厚并富集了水和大离子亲石元素的陆下岩石圈获得了地球化学上的不稳定性,在伸展构造环境(可能有多期伸展)驱动下,脱水熔融以达到稳定的趋势,在这个过程中,其化学成分将逐渐与古老陆下岩石圈地幔的化学成分趋于一致。因此,水化的陆下岩石圈地幔在伸展过程中的低程度批式脱水部分熔融,形成的富含金属和水的高分异型岩浆构成了成矿岩浆,并在岩石圈的不同尺度经过多阶段结晶分异-同化混染后,就位成为近矿岩浆房。陆下岩石圈脱水熔融的结束也意味着巨型热液钼矿化作用的结束,并决定了俯冲后巨型热液成矿带总的生命周期,这也与兴蒙造山带及华北板块北缘钼矿化(甚至其他热液型矿化)在早白垩世(约130 Ma)趋于减弱并熄灭的现象一致,也使得新生代的碱性岩浆岩不具有显著的脱水熔融特征。综上,笔者认为兴蒙造山带及华北板块北缘的斑岩钼矿化为一个统一的整体,属于古亚洲洋俯冲作用水化的源区在后期强烈伸展环境下部分熔融的产物,是古亚洲洋俯冲成矿作用的延续和发展,也是古生代塑造的富集型源区在中生代伸展构造驱动下的复合成矿作用。
[Abstract]:There are 1 Mesozoic porphyry molybdenum metallogenic belt was xing'anling-mongolian orogenic belt and the South affected by the southward subduction of the paleo Asian Ocean in the northern margin of the North China plate, and in the end to end things on both sides. This article reviews the advances in research of porphyry molybdenum deposit in extensional environment, distribution of metallogenic background, xing'anling-mongolian orogenic belt and North China plate in the northern margin of 2 molybdenum metallogenic belt, ore assemblage characteristics, metallogenic magma properties, massive metal and water sources and porphyry copper molybdenum mineralization, the similarities and differences are summarized, and the process of shaping the source region from magma angle discusses the formation characteristics of giant molybdenum mineralization. This 2 mo geological characteristics and metallogenic belt in the area of deposits are very similar, which is similar to the start time and the peak time, the porphyry copper mineralization and regional features not in the era of symbiosis, with the United States Department of mineralization The high F type porphyry molybdenum of Colorado area output similar to that of the two constitute a unified whole. Element geochemical study showed that the south, north 2 molybdenum metallogenic belt and Paleozoic porphyry copper metallogenic magmatic metallogenic magma and Mesozoic alkaline magma have similar characteristics, as a result of dehydration melting, and with the ancient subcontinental lithospheric mantle xenoliths, Cenozoic asthenospheric mantle basalt has significant difference. Studies suggest that the magma source region south molybdenum ore belt is the loss of metal and water ancient magma source in the product of Paleozoic subduction process account after the transformation of foreign films dehydration, North molybdenum ore belt of the magma source region is rich in water source area Paleozoic ocean subduction accretion formation. (including) the study of isotope rock Sr display, South, north 2 metallogenic source region molybdenum metallogenic belt are starting source area in the low Rb/Sr ratio, high ratio of Rb/Sr contaminated by upper crust; Nd Comparative study of element feature shows that two of the initial Nd value vary greatly, but the ratio of Sm/Nd is very similar to that radiogenic Nd accumulation was consistent in the later Triassic, also shows that the initial Nd value of the difference is the ore forming source region shape before and inheritance, also said that the beginning of the Nd difference may to cover up the real reason of the Mo mineralization magma formation. Through the comparative study, and the world within the scope of other typical molybdenum metallogenic belt that South, north 2 metallogenic mineralization belt of the magma source area is located in the continental lithospheric mantle, Paleozoic paleo Asian Ocean to the South and north sides of the subduction plays an important role in the process of its formation. Mainly reflected in the shape of enrichment type source region, several water orogenic belt and so on. The subduction of thickened lithosphere transformation, thickened and enriched water and large ion lithophile elements of Subcontinental Lithosphere obtained geochemical instability Qualitatively, in extensional tectonic environment (possibly extension) driven by dehydration melting in order to achieve a stable trend, in this process, the chemical composition of the chemical composition and the ancient subcontinental lithospheric mantle gradually tend to be consistent. Therefore, the hydration of subcontinental lithospheric mantle in the extensional process in low degree batch dehydration partial melting, high profiled metal rich magma formation and water formed in different metallogenic magma, and the lithosphere scale after several stages of crystallization differentiation assimilation after emplacement of magma chamber. The ore becomes near end lithosphere also means that dehydration melting hydrothermal mineralization over giant molybdenum. And determine the giant HYDROTHERMAL METALLOGENIC BELT subduction after the total life cycle, this also with the Xing Meng orogenic belt and the northern margin of the North China plate and molybdenum mineralization (or other hydrothermal type mineralization) in the early Cretaceous (about 130 Ma) tends to weaken and extinguish the phenomenon Same, also makes the alkaline magmatite Cenozoic has no significant features of dehydration melting. To sum up, the author thinks that the porphyry molybdenum mineralization of xing'anling-mongolian orogenic belt and the northern margin of the North China plate as a whole, the source region belongs to the subduction of the paleo Asian ocean water strong extension in the products of partial melting of environment in later period. Is the continuation and development of the paleo Asian Ocean subduction metallogeny, enrichment type source region is shaped in the Paleozoic Mesozoic extensional tectonic complex mineralization driven.

【作者单位】：中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室;
【基金】：国家“973”项目(编号:2013CB429805) 国家自然科学基金项目(编号:41302057,41273061) 中央级公益性科研院所基本科研业务费项目(编号:K1311) 地质调查局地质大调查项目(编号:121201004000150009)联合资助
【分类号】：P618.65

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