發(fā)布時間：2018-04-16 07:42

  本文選題：巖漿混合 + 薛家石梁　； 參考：《中國地質大學(北京)》2017年碩士論文

【摘要】：薛家石梁雜巖體位于華北克拉通中部,北京地區(qū)燕山山脈南麓,由五個小巖體組成,按年齡從早到晚依次為上莊巖體、薛家石梁巖體、黑山寨巖體、湖門巖體和黑熊山巖體,其中薛家石梁巖體和黑山寨巖體中含有大量閃長質包體及伴生的細粒閃長巖巖脈。上莊巖體由四種巖石組成,從下至上分別為橄長巖、輝長蘇長巖、輝長巖和輝長閃長巖,其中橄長巖和輝長蘇長巖中富含鈦磁鐵礦礦體,并與橄長巖互層狀產出;薛家石梁巖體主體巖性為角閃閃長巖,在靠近上莊巖體和黑山寨巖體邊界附近為輝石閃長巖;黑山寨巖體為角閃二長巖,靠近湖門巖體邊界附近為黑云母二長巖;湖門巖體為正長巖,由北向南巖石中礦物粒徑逐漸減小,顯示其冷凝速度不均衡;黑熊山巖體主體巖性為正長花崗巖-二長花崗巖。五個小巖體中除了薛家石梁巖體和黑山寨巖體為過渡型接觸帶外,其他巖體之間均為侵入接觸關系。按照馬昌前等(1994)的包體分類,將薛家石梁雜巖體中的包體分為混雜包體和混成包體兩類,并通過對包體和巖脈及寄主巖的巖漿粘度、密度計算,并結合巖相學特征和主量元素Harker圖解分析,得出薛家石梁巖體內靠近上莊巖體邊界附近發(fā)生巖漿機械混合作用,混合區(qū)域內所含包體為混雜包體,黑山寨巖體內部也可見到與之成分相同的混雜包體,也為機械混合作用的結果,而黑山寨巖體與薛家石梁巖體的過渡型接觸帶為巖漿化學混合作用的結果,接觸帶內所含包體為混成包體,其中薛家石梁閃長質巖漿所占比率較高,最高可達76%。薛家石梁巖體、黑山寨巖體和湖門巖體的稀土元素、微量元素的配分曲線近似平行,顯示三者具有相同的源區(qū),富集Ba、Sr、Nb、Ta元素和虧損Pb元素暗示三個巖體來源于下地殼并有幔源物質混入。薛家石梁巖體與黑山寨巖體內的混雜包體的稀土元素和微量元素配分曲線一致,且與上莊巖體的配分曲線近于平行,結合上莊橄長巖中發(fā)育大量斜長石殘留晶的證據(jù),暗示該混雜包體為富鐵含礦流體灌入到上莊巖體中發(fā)生部分熔融的產物,部分熔融溫度在1130℃以上。通過SHRIMP鋯石U-Pb測年,測得混雜包體年齡為127.5Ma,比薛家石梁巖體大約晚3Ma,暗示華北克拉通的抬升速度很快,是巖石圈拆沉作用的直接響應。
[Abstract]:The Xuejia Shiliang complex is located in the central part of the North China Craton, and the southern foot of the Yanshan Mountains in Beijing area. It consists of five small rock masses, which are the Shangzhuang rock mass, the Xuejialiang rock body, the Heishanzhai rock body, the Humen rock body and the Heixiong mountain rock body from early to late according to the age.There are a large number of diorite inclusions and associated fine diorite veins in the Xue Jia Shiliang and Heishanzhai rocks.The Shangzhuang rock body is composed of four kinds of rocks, which are olivine, pyroxene, gabbro and pyrodiorite from the bottom to the top, among which the olivine and pyroxenite are rich in titanomagnetite ore bodies and interbedded with olivine.The main lithology of the Xue Jia Shiliang rock body is hornblende, near the boundary of Shangzhuang and Heishanzhai rock bodies is pyroxene diorite, the Heishanzhai rock body is hornblende monzonite, and near the boundary of Humen rock body is biotite monzonite.The Humen rock body is a syenite, and the size of minerals in the rock decreases gradually from north to south, which indicates that the condensation velocity is uneven, and the lithology of the main body of the Heixiongshan rock body is syenite-monzogranite.In the five small rock masses, except Xue Jia Shiliang and Heishanzhai rock bodies are transitional contact zones, the other rock masses are intrusive contact relationship.According to the classification of inclusions in Machang Qianliang (1994), the inclusions in Xue Jia Shiliang complex are divided into two types: hybrid inclusions and mixed inclusions. The magmatic viscosity and density of inclusions and veins and host rocks are calculated.Combined with petrographic characteristics and principal element Harker diagram analysis, it is concluded that magmatic mechanical mixing occurs near the boundary of Shangzhuang rock body in Xue Jia Shiliang rock body, and the inclusions contained in the mixing area are mixed inclusions.In the interior of the Heishanzhai rock mass, the same mixed inclusions are also found, which are also the result of mechanical mixing, while the transitional contact zone between the Heishanzhai rock body and the Xue Jia Shiliang rock body is the result of the chemical mixing of magma.The inclusions contained in the contact zone are mixed inclusions, of which the ratio of Xue Jialiang diorite magma is high, the highest is 76g.The distribution curves of rare earth elements and trace elements in the Xue Jia Shiliang, Heishanzhai and Humen rock bodies are approximately parallel, indicating that the three bodies have the same source region.The enrichment of Ta and Pb suggests that the three intrusions are derived from the lower crust and are mixed with mantle materials.The REE and trace element partitioning curves of the xenoliths in Xue Jia Shiliang and Heishanzhai rocks are consistent, and are nearly parallel to those of the Shangzhuang rock mass, and combined with the evidence that a large number of plagioclase residual crystals are developed in Shangzhuang olivine.It is suggested that the hybrid inclusion is the product of partial melting of the iron-rich ore-rich fluid into the Shangzhuang rock mass, and the partial melting temperature is above 1130 鈩，

本文編號：1757899