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铜绿山Fe-Cu(Au)矿床是长江中下游铁铜成矿带最重要的矽卡岩型矿床之一,矿床的形成与铜绿山石英闪长岩岩株有关.矿区东南部发育有花岗伟晶岩,其形成时间介于石英闪长岩和矽卡岩之间.花岗伟晶岩主要由钾长石、斜长石和石英组成;由石英和钾长石组成的文象结构非常发育.激光阶段加热40Ar/39Ar定年表明,花岗伟晶岩的侵位时间为136.5±0.7Ma(2σ),与石英闪长岩的侵位时代和铜绿山矿床的成矿时代完全一致.铜绿山石英闪长岩与花岗伟晶岩的钾长石具有非常相似的主量元素,平均组成分别为Or81Ab18和Or78Ab21.根据岩相学观察和地球化学分析认为,花岗伟晶岩中的文象结构是在快速冷却体系条件下、钾长石晶体生长边界层的SiO2和Al2O3浓度因生长不平衡发生周期性变化而导致石英和钾长石交替生长形成的.铜绿山石英闪长岩和花岗伟晶岩中钾长石的大离子亲石元素(LILE)含量均较高,但与前者相比,花岗伟晶岩中钾长石的Rb、Pb含量明显增加,Ba、Sr含量显著降低,Li、Cs含量略微降低.大离子亲石元素图解(Rb-Ba、La-Ba、K/Ba-Ba、Rb/Sr-Ba)指示花岗伟晶岩是铜绿山石英闪长岩岩浆晚期高度结晶分异演化的结果.但花岗伟晶岩钾长石中Pb、Li、Ga等元素的变化却与岩浆结晶分异演化趋势相悖,表明流体作用在花岗伟晶岩的形成过程中扮演了重要角色.花岗伟晶岩中的石英发育大量熔融包裹体和高盐度流体包裹体,后者的均一温度为260～435℃,进一步证实花岗伟晶岩是从流体-熔体共存体系中结晶的.
The Tonglushan Fe-Cu (Au) deposit is one of the most important skarn deposits in the iron-copper metallogenic belt in the middle and lower reaches of the Yangtze River, and the formation of the deposit is related to the Tongshushan quartz diorite rock mass.The granite Pegmatite, formed between quartz diorite and skarn.The granitic pegmatite is mainly composed of potash feldspar, plagioclase and quartz; the compositional structure of quartz and potassium feldspar is very developed 40Ar / 39Ar dating shows that the emplacement time of granitic pegmatite is 136.5 ± 0.7Ma (2σ), which is consistent with the emplacement age of quartz diorite and the age of Tonglushan deposit. Quartz-diorite and granitic pegmatite have very similar main elements of K-feldspar, the average composition of Or81Ab18 and Or78Ab21 respectively. According to petrographic observation and geochemical analysis, the text of the granitic pegmatite The structure is that under the condition of rapid cooling system, the concentration of SiO2 and Al2O3 in the growth boundary layer of K-feldspar grows alternately due to the imbalance of growth period, resulting in the alternating growth of quartz-KfD and granite Pegmatite in the K-feldspar large ion lithophile element (LILE) However, compared with the former, the contents of Rb and Pb, the content of Ba and Sr, and the content of Li and Cs in potassium feldspar of granitic pegmatite increase obviously, and the content of Rb and Pb Baa, La-Ba, K / Ba-Ba and Rb / Sr-Ba) indicate that the granitic pegmatite is the result of the late stage high-level crystallization differentiation of the Tertiary magmatic quartz diorite magma. The changes of Pb, Li, Ga and other elements in the rocks are contrary to the differentiation evolution of magma crystals, indicating that the fluid plays an important role in the formation of granitic pegmatites. The quartz in granitic pegmatites develops a large amount of melt Inclusions and high-salinity fluid inclusions, the latter with a homogenization temperature of 260 ~ 435 ℃, further confirming that granitic pegmatites crystallize from the fluid-melt coexistence system.