摘要:
内生金属成矿系统被认识到是一种复杂性动力系统,而成矿作用则是一种非平衡、非线性过程.在这种理论框架下,成矿作用首先是一种物理过程,成矿系统是一种流体驱动的地质子系统.小体积岩浆系统也是一种流体驱动的地质子系统,因而小岩体与内生金属成矿作用具有内在的联系,揭示小岩体与成矿作用的内在联系是实践复杂系统成矿理论的关键环节.笔者列举了流行岩浆热液成矿理论的一些常见矛盾,阐明了小岩体成大矿学说的重要意义.基于岩浆系统时空结构的分析,小岩体可以划分为无根小岩体和有根小岩体,后者可以进一步划分为头部小岩体和通道小岩体.由于流体中成矿金属的溶解度与P-T呈正相关,大型-超大型矿床主要与无根小岩体有关.在小体积岩浆成矿系统中,透岩浆流体起了关键作用.透岩浆流体不仅向岩浆体注入了大量成矿金属,也是岩浆快速上升的触发机制和多源区近同时部分熔融的根本原因.这种特征决定了小岩体往往呈岩体群产出,而不是孤立的单个岩浆侵入体.岩浆快速上升造就了成矿期的近场应力场以主压应力分布在竖直方向为特征,后者进一步决定了小岩体群的空间展布形式.据此,小岩体可作为有效的可填图找矿标志.可以说,小岩体成大矿学说为研究岩浆动力学打开了新的窗口,是区域成矿预测的基本依据和重塑内生金属矿床成矿学的里程碑.
Abstract:
It is recently recognized that the ore mineral system is a complex dynamic system,and that the min-eralization is of a non-equilibrium and non-linear process.Based on this theoretic framework,the mineralization is primarily a physical process,and the mineral system is a fluid-driven geological sub-system.The magma system with small volume is also of a fluid-driven geological sub-system.Therefore,there exist instinct relations between the small intrusions and the endogenic mineral deposits,and revealing such relations is the key to practice the metallogenic theory in complex systems.Listing some common contradictions in the prevailing magmatic-hydrothermal theory,it is emphasized that the hypothesis of metallogeny by the small magmatic intrusion has important theoretical and practical significances.Based on the pattern of spatio-temporal structure of the magmatic system,the small intrusion can be divided into the un-rooted and rooted intrusions,and the later is further divided into the head intrusion and the channeling intrusion.Because the solubility of ore-forming metals in geofluids positively relates to the values of temperature and pressure,the giant ore deposits are generally associated with the un-rooted minor intrusion.In such a magmatic ore system,the transmagmatic fluids take place crucial roles for producing ore bodies.The magmatic fluid not only injects the ore-forming metals into the magma system,but also triggers the magma to ascend quickly,and causes contemporaneous partial melting at the different depth levels.These features determine that the small intrusions often occur as a swarm instead of in individual magmatic body.Due to rapid upwelling of the melt-fluid flow,the co-metallogenic local stress field in a ore field characterizes that the main compressional stress axis is located in the vertical direction,which further determines the spatial pattern of the small intrusions.Accordingly,the small intrusion swarm is an efficient and mappable perspective element.Therefore,it can be said that the theory of metallogeny by the small magmatic intrusion opens new windows for improving magma dynamics,and is one of targeting elements for the regional prognosis of mineral deposits and a milestone from which new departures in the economic geology would be started.
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