【作者】 楼亚儿；

【导师】 杜杨松；

【作者基本信息】 中国地质大学（北京） ， 矿物学、岩石学、矿床学， 2005， 博士

【摘要】 繁昌地区位于安徽铜陵市东北部,属于长江中下游铁、铜、钼、金成矿带的一部分。燕山期中酸性岩浆侵入活动频繁而强烈。通过深入研究繁昌地区典型岩体的岩相学、矿物学和岩石地球化学等方面的特征,并与前人在毗邻的铜陵地区获得的侵入岩资料进行对比分析,对侵入岩的成因进行了深入探讨,取得了下列成果。 1.用锆石SHRIMP法精确测定了繁昌侵入岩的形成年龄为124.3 Ma和125.3Ma,铜陵侵入岩的SHRIMP年龄分别为135.5Ma、139.5Ma,因而确定繁昌侵入岩的形成比铜陵岩体至少要晚十几百万年。并且在滨江花岗岩体中发现了年龄比较老的继承锆石,其SHRIMP年龄数据为1049±29 Ma,相当于中元古代变质基底的年龄。从阴极发光照片可以看到,该颗粒锆石有明显的核,可能是继承或捕获锆石。由此可以推断年龄大的锆石是由岩浆在上升过程中带入其中的,这从一个侧面证明了岩浆是由上地幔上侵而进入下地壳,然后经过运移侵入到上地壳的。 2.繁昌侵入岩的岩性为黑云母石英二长岩、石英闪长岩至花岗岩,但以花岗岩为主,岩性偏酸性,SiO₂含量、K₂O含量明显比铜陵地区中生代侵入岩的要高,属于富K钙碱性花岗岩类,岩体的结晶分异现象十分明显,形成不同的岩相带。 3.从Rb-Sr,同位素特征来看,侵入岩的I₀值在0.707161～0.708312之间,均为壳-幔混源型来源。且滨江岩体钾长石的铅同位素值与凤凰山岩体钾长石和沙滩脚岩体斜长石的铅同位素值非常接近,表现为明显的地幔岩浆和下地壳岩浆的混合特征。 4.从不同岩体和矿物的稀土特征来看,繁昌侵入岩的稀土总量总体较高,轻重稀土分馏比较明显,轻稀土较为富集,重稀土曲线较为平坦,且有弱的负铕异常。繁昌侵入岩的稀土配分曲线与铜陵凤凰山花岗闪长岩的稀土配分曲线基本相似,暗示两区岩石具有相同或相似的成因。两地区岩体中的黑云母成分表明它们均属壳-幔混源型。 5.从微量元素分析来看,繁昌岩体的不相容元素Zr/Y、Zr/Nb值均小于18。同时,在滨江花岗岩中分离出大量的金红石,表明岩体含Ti高,来源比较深,可能为偏碱性（钙碱性）的花岗岩,并且形成在板内张开的裂谷构造环境。 6.提出繁昌和铜陵地区中生代侵入岩经历了相似的形成过程的看法。 7.通过稀土成分分析、电子探针成分分析和X射线衍射分析,确定产于花岗岩和火山熔岩中并被前人鉴定为硅铍钇矿(FeY₂[Be₂Si₂O₁₀])的矿物实际上分别是金红石和石榴石,这对认识区域岩浆起源和演化有重要意义。更多还原

【Abstract】 The Fanchang area, located in northeastern Tongling City of Anhui Province, is a segment of the iron, copper, molybdenum and gold metallogenic belt in Middle and Lower Reaches of the Yangtse River. There occurs many Mesozoic magmatic intrusions. A petrographic, mineralogical, petrochemical and geochemical study combined with a field geological investigation has been conducted on these intrusions. Some important conclutions have been drawn based on the study and investigation.1. The lithologies of the intrusions in Fanchang area include biotite quartz monzonite,quartz diorite and granite, and the contents of SiO2 and K2O in these rocks are higher than those in intrusive rocks in the Tongling area. The rocks are K-rich alkaline granitoid.2. Some of the zircon grains from Binjiang granite and Banshiling biotite quartz monzonite intrusions yield 207Pb/206Pb ages of 124.3-125.3 Ma, while those from the intrusions in Tongling yield the ages of 135.5—139.5Ma. Evidently, the instrusions in Fanchang were formed over 10 Ma later than those in Tongling . Moreover, an inherited zircon sorted from granite in the Binjiang intrusion yields the age of 1049+ 29 Ma, indicating that it might be taken by an evolved magma from the oldest metamorphic basement to upper crust.3. The initial 87Sr/86Sr ratios of the samples from the Fanchang instrusions range from 0.707161 to 0.708312, and samples of K-feldspar from the Binjiang granite and Fenghuangshan granodiorite intrusions and ones of plagioclase from Shatanjiao granodiorite intrusion have a similar composition of Pb isotope. This supports derivation of these instrusions in the two areas from a mixing source of mantle and crust.4. The magmatic rocks from the intrusions in Fanchang and Tongling have similar REE distribution patterns with high value of Σ REE, enrichment of LREE and weak更多还原