晋东北燕山期岩浆活动与金多金属成矿作用动力学

Yanshanian magmatism and gold-polymetallic mineralization dynamics in northeastern Shanxi Province,China

晋东北燕山期岩浆活动受区域性构造控制,具有北东成带,带内成区的分布规律,时间上可划分为150～160Ma、130～140Ma和85～127Ma三个高峰期。岩浆岩可划分为以花岗闪长岩—二长花岗岩—中细粒-粗粒斑状黑云母花岗岩等和以闪长岩—花岗闪长斑岩—花岗斑岩—石英斑岩等为主体的两大岩石组合,后者与金多金属矿床成矿关系密切。主要岩浆岩为过铝质碱性岩类,具有埃达克质岩石的亲和性;成因上属于I型,具同源演化关系。其形成可能与华北板块中生代岩石圈大规模减薄所引发的壳幔相互作用密切相关。与燕山期岩浆活动相对应,区域金多金属成矿也具有集中分布和多期成矿的特点。在类型上,主要包括斑岩型Mo-Au矿床、矽卡岩-热液脉型Au、Fe矿床和爆破角砾岩-热液石英脉型Au或Cu-Ag,Ag-Pb-Zn等矿床。有时在同一个成矿集中区内可见有多型一体的复杂组合,并在空间上具有明确的元素分带关系;在时间上,150～160Ma,主要与(二长)闪长岩或石英闪长岩、花岗闪长岩等有关,形成以钼-金为主的矿化;130～140Ma,主要与石英闪长岩、石英斑岩等有关,形成大规模金矿化;85～127Ma,主要与花岗斑岩、石英斑岩、隐爆角砾岩等相关,形成了强烈的银多金属矿化。不同类型矿床成矿热液主要源自相关的岩浆体系。华北板块中生代发生区域性构造体制转折,岩石圈大规模减薄及在此背景下发生的陆内造山作用是区域大规模岩浆活动和成矿作用的重要动力学机制。

The Yanshanian magmatism in the northeastern part of the Shanxi Province,controlled by regional structures,occurred as northeast belt with local concentrations.These magmatic rocks,formed in three pulses at 150～160Ma,130～140Ma and 85～127Ma,can be grouped into two suits.The former suit is comprised of granodiorite,monzongranite and coarse grain porphyritic biotite granite.The later suit is composed of diorite,granodiorite porphyry,granitic porphyry and quartz porphyry.The later suit shows close relationship to gold and basic sulfide mineralization.Most of these magmatic rocks are peraluminous and alkaline rocks with adakite affinity.These rocks belong to I-type and were evolved from same source.The formation of these granitic rocks was probably related to crust-mantle interaction triggered by lithosphere thinning of the North China Craton in Mesozoic.Related to the Yanshanian magmatic activities,mineral deposits also show concentration and multi-stage mineralization.The mineral deposit types include porphyritic Mo-Au,skarn-hydrothermal vein Au,Fe,and explosive breccia-hydrothermal quartz vein type Au or Cu-Ag,Ag-Pb-Zn deposit.Some of these types were overlapped sometimes in the same area and show spatial zone in elemental distributions.The Mo-Au mineralization was in 150～160Ma and is related to the monzondiorite or quartz diorite,granodiorite.The Au mineralization was in 130～140Ma,and is related to quartz diorite and quartz porphyry.Ag and basic sulfide mineralization were in 85～127Ma,and is related to granitic porphyry,quartz porphyry and explosive breccia rocks.Hydrothermal fluid responsible for this mineralization was soured from related magmatic activity.These metallic mineralization were genetically related to the tectonic regime transition of North China Craton in Mesozoic,lithosphere thinning,and inner land orogenesis and large scale magmatic activities.