河南嵩县牛头沟地区花岗岩岩浆源区及形成机制

发布时间：2018-07-01 18:38

  本文选题：地球化学 + 锆石U-Pb年代学　； 参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：河南嵩县牛头沟矿田中发育多条花岗岩脉,岩性包括花岗斑岩和斑状二长花岗岩。为查明矿田中花岗岩的形成年代、机制和构造背景,本次工作系统采集了松里沟、沙土洼和下庄花岗斑岩,以及沙土洼和木耳沟斑状二长花岗岩,并进行了岩相学、地球化学、年代学和Hf同位素组成研究,取得如下成果和认识:(1)松里沟和下庄花岗斑岩为钙碱性、高钾岩石,沙土洼花岗斑岩和斑状二长花岗岩为碱性、钾玄岩系列岩石。该区花岗岩均富集大离子亲石元素Rb、K、亏损高场强元素Nb、Ta、Ti、P,还主要表现出负Eu异常的特点,其中的花岗斑岩亏损中稀土,而斑状二长花岗岩亏损重稀土。(2)松里沟、沙土洼花岗斑岩和沙土洼、木耳沟斑状二长花岗岩形成于168.8±4.1Ma、162.6±5.7Ma和166.8±1.6Ma、163.1±2.3Ma。结合前人研究,限定牛头沟矿田花岗质岩浆的活动时限为160~169Ma。(3)松里沟、沙土洼、下庄花岗斑岩和沙土洼、木耳沟斑状二长花岗岩的εHf(t)为-24.43~-19.79、-24.10~-20.92、-24.18~-20.17和-22.96~-15.84、-21.35~-16.04;TDM2为2434~2718Ma、2511~2706Ma、2473~2720Ma和2190~3140Ma、2198~2566Ma。它们是古老地壳物质太华群部分熔融的产物,为I型花岗岩。(4)沙土洼和木耳沟斑状二长花岗岩主要是角闪岩和斜长角闪岩在800~850℃、1.4~1.7GPa下部分熔融的产物,岩浆源区的残留相矿物可能为石榴子石、金红石、钛铁矿,少量单斜辉石、角闪石和斜长石。松里沟和下庄花岗斑岩的原岩是黑云斜长片麻岩、TTG片麻岩中的偏酸性部分和钾长花岗片麻岩,沙土洼花岗斑岩的原岩主要是角闪岩和斜长角闪岩,它们是在707~728℃、687~743℃、718~737℃和较低压力条件下部分熔融形成,岩浆源区的残留相矿物可能为斜长石、角闪石和磷灰石。(5)牛头沟矿田花岗岩的形成与古太平洋板块西向俯冲、岩石圈伸展、软流圈上涌有关。
[Abstract]:There are many granite veins in Niutougou ore field, Songxian, Henan Province. The lithology includes granitic porphyry and porphyry monzogranite. In order to find out the age, mechanism and tectonic setting of granites in the ore field, Songligou, Shatuwa and Xiazhuang granitic porphyry, as well as sandy and muergou porphyry granites, were collected in this work system, and the lithofacies and geochemistry were carried out. The results of geochronology and HF isotopic composition are as follows: (1) the Songligou and Xiazhuang granitic porphyry rocks are calc-alkaline, high-potassium rocks, shatuwa granitic porphyry rocks and porphyry granitic granites are alkaline, and kaliacite series rocks. The granites are rich in large ion lithophile elements RbLi K and depleted in high field strength element Nbtadao TiTiP.It also shows the characteristics of negative EU anomaly, in which granitic porphyry depleted rare earths, while porphyry granites depleted heavy rare earths. (2) Songligou, In Shatuwa granitic porphyry and Shatuwa, Muergou porphyry monzonitic granites were formed at 162.6 卤5.7 Ma and 163.1 卤2.3 Ma at 168.8 卤4.1 Ma and 166.8 卤1.6 Ma, respectively. In combination with previous studies, the time limit of granitic magma activity in the Niutougou Orefield is 160- 169Ma. (3) Songligou, Shatuwa, Xiazhuang granitic porphyry and sandy soil depression, the 蔚 HF (t) of the porphyry monzogranites in Muergou are -24.43U -19.79U -24.10-20.92- 24.18CU -20.17 and -22.96- 15.84W -15.84W -21.356Ma TDM2: 24342718Ma 25112706Ma 2511732720Ma and 2190NU 3140MaA 1982D 2566Ma. They are the product of partial melting of the ancient crustal material Taihua Group and belong to I-type granite. (4) the Shatuwa and Muergou porphyry monzomorphic granites are mainly the product of partial melting of amphibolite and amphibolite under 800 ~ 850 鈩，

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