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隐伏岩体顶上带与深部成矿预测

ISSN号：1671-2552
期刊名称：《地质通报》
时间：0
分类：P588.12[天文地球—岩石学;天文地球—地质学] P612[天文地球—矿床学;天文地球—地质学]
作者机构：[1]浙江省地勘局第三地质大队／浙江省核工业二六九地质大队,浙江金华321017, [2]中国地质大学地球科学与资源学院,北京100083
相关基金：国家自然科学基金项目（编号：40573033）和重大计划项目（编号：90914002）资助

关键词：岩浆岩顶上带, 深部成矿预测, 流体流动, 二次沸腾与减压, 直立长椭球状侵入体, top zone of magma body, deep area ore-prospecting, fluid flowing pattern, secondary boiling and decompression, vertically elongated intrusion

中文摘要：

岩浆侵入的流体流动模拟表明，侵入体上方是流体聚焦流动的位置，流体通量远大于旁侧围岩，流体在此产生沸腾作用。随温度降低，侵入体上方渗透率逐渐增大，最大渗透率出现在侵入体的顶部。含水岩浆侵位后在其顶上带发生二次沸腾和减压过程，释放出的巨大机械能远大于围岩的抗张强度，足以引起围岩发生脆性破坏。岩浆岩顶上带的水饱和外壳及其围岩发生破裂形成陡倾裂隙和水力破裂。直立长椭球状岩浆体的侵入会在岩浆岩顶上带产生放射状和同心圆状裂隙．同时产生爆破角砾岩筒。因此侵入体顶上带的岩钟、岩枝、岩脉，放射状、同心圆状裂隙和角砾岩筒均为构造弱化带，是热液矿脉密集发育的部位。矿床地质学研究已充分证明，岩浆岩顶上带确是容纳与中酸性岩浆有关的热液矿床的最佳部位。在开展深部成矿预测和找矿的过程中，探寻隐伏岩体顶上带和／或岩钟，是寻找深部与花岗岩类有关的多金属矿床的捷径。

英文摘要：

The simulation of magma fluid flowing in and around granite plutons indicates that the top zone, apical or cupola of intrusion are the locations of focused fluids flow, where fluid flux is larger than the lateral wallrock. After the emplacement of hydrous magmas, two sequential processes play critical roles： the process of second boiling and decompression. The mechanical energy released in the second boiling exceeds the maximum tensile strength of the wallrock, which can produce extensive fracture failures. Because the axis of least principal stress in the shallow crustal environment generally lies essentially in the horizontal plan, failure of the roof rocks including the H2O-saturated carapace and wallrock produces myriad steeply dipping fractures and hydro-fracturing. The cupola and apical of magma body and the radial and concentric fracture systems, breccia pipes occurred in and around prolate magma body are structural weak zones, they can provide excellent accomodation for granite-related hydrothermal minerals. During the prospecting of hidden and concealed granite-related polymetaUic deposits, it is a shortcut to explore the top zone or cupola of hidden intrusions.

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