【摘要】 胶东被视为全球惟一一个晚于赋矿围岩几十亿年而发生巨量金聚积的矿集区,也是中国最重要的黄金基地,已发现金矿床150余处,累计探明黄金资源储量超过4500t。金矿床沿区域上NE-NNE向断裂带及其次级断裂产出,具有NE呈带、EW呈行的分布特征,形成招莱、蓬栖、牟乳和盆缘4条金矿带。控矿断裂带经历了从挤压、经剪压和剪张、到伸展的构造体制转换,其中成矿前为挤压-剪压构造体制,成矿后为伸展构造体制,而大规模金成矿作用受控于NNW-SSE向主构造应力场引起的韧-脆性形变,形成于剪压-剪张构造体制转换过程中。区域控矿断裂带具有拆离断层特征,且在成矿期与上、下盘的构造-建造组合具有变质核杂岩典型的3层组成结构,其中受控于拆离断层脆-韧性变形的玲珑变质核杂岩东缘金矿床的金矿化年龄略早于受控于脆性构造变形的区域大规模金成矿作用,表明至少存在两次连续却明显不同的金成矿事件,其形成于陆内伸展拆离向汇聚挤压构造体制转换背景。成矿前、后,区域主构造应力场基本均一,反映了区域均匀应变特征;而成矿期NE-NNE向断裂带叠加于再活化的近EW向基底构造之上,触发区域控矿的NNE向断裂带往NE方向偏转了约20°～30°,引起构造主应力偏离区域等效应力10°～20°,导致局部非均匀应变和围岩渗透率的增大,从而有利于巨型金矿床(区)的形成与就位。压剪构造体制下断层产状相对平缓的部位呈拉张状态,导致断裂带下盘形成厚且宽的含赤铁矿钾化蚀变带,其化学和流变学特征有利于随后金成矿作用的发生,是破碎带蚀变岩型金矿床NE向控矿断层倾角相对较缓的可能原因;而由断块旋转变形导致的近平行S-N向高角度断裂带间先存构造薄弱带的再活化和液压致裂作用是导致石英脉型金矿床形成与就位的可能机制。更多还原

【Abstract】 Jiaodong peninsula was considered as the only district with giant gold resources that postdates billions of years of the wall-rocks. It is also the most important gold base of China, with more than 150 gold deposits and proven gold resources of over 4500 tons. These gold deposits occur along the regional NE-NNE-trending faults and their secondary faults, and are distributed as NE-trending belts and EW-trending zones. The ore-controlling NE-NNE-trending faults experienced structural transition of the initially compression, to shear-compression and shear-extension, and finally extension. The pre-ore stage was controlled by the compressional and shear-compressional structures, while the post-ore stage was controlled by the extensional structures. These two stages share consistent regional main stress field,indicating the homogeneity of regional deformation. The massive gold mineralization was controlled by the ductile-brittle deformation under the NNW-SSE-trending main stress field, and formed during the transition of shear-compression to shear-extension. Gold deposits in the eastern margin of the Linglong metamorphic core complex were controlled by the brittle-ductile deformation of detachment fault, with mineralized ages of 130–126 Ma, which was earlier than the brittle deformation controlled massive gold mineralization at ca. 120 Ma. Moreover, the current main stress field near the E-W trending corridor deflected to NEE direction of ca. 20°, indicating that the ore-controlling NNE-trending fault deflected to NE direction of ca. 20°–30°. It is cryptically evidenced that these jogs line up in the E-W trending corridor due to reactivation of Paleoproterozoic to Mesozoic faults and folds that were part of the structural architecture of the terranes prior to the gold mineralization. These jogs induced deviations in the local principal stresses, and resultant heterogeneous strain, which increased the rock permeability, and favored the influx of ore-forming fluids and enrichment of gold. At the deposit scale, the gold deposits of disseminated/microbrecciastockwork type are commonly situated below relatively gently-dipping segments of NE-trending faults; whereas more steeply-dipping segments are poorly mineralized. Transpression may lead to dilation of the gentle-dipping segments and widespread hematite-bearing K-feldspar pre-ore alteration of the rocks below the faults, which are chemically and rheologically favorable for subsequent gold-mineralization. The N-S corridors of vein-type gold deposits are interpreted to be related to reactivation and fracturing of pre-existing weaknesses.更多还原