阿尔金南缘江尕勒萨依二长花岗岩年龄测定毕业设计论文Word下载.docx

1、反映该花岗岩的源岩主要来自于壳源物质的重熔，其来源也相对单一。江尕勒萨依二长花岗岩稀土总量为中等（REE = 180.89 ppm 260.17 ppm）,具有高度富集轻稀土而亏损重稀土的特征, 轻重稀土比值高（LR/HR=9.01 22.14, 平均为20.59）, （La/Yb）N = 14.18 89.35, 平均为74.68, 样品均出现明显的负Eu异常（Eu =0.16 0.36, 平均为0.25）从微量元素对原始地幔标准化蛛网图上可以看出, 所有花岗岩样品富集KRbTh和U等大离子亲石元素（LILEs）与轻稀土元素（LaCeNd等）, 亏损NbTaP和Ti等高场强元素（HFSEs）

2、, 具有明显的Sr与Ba负异常, ZrHf无明显分异, SrBa亏损与负的Eu异常, 共同表明部分熔融源区残留体中存在斜长石或在岩浆演化过程中斜长石发生分离结晶该地区花岗岩样品中的锆石自形程度为自形晶, 呈长柱状从CL图像可以看出, 锆石显示清晰的岩浆振荡环带。锆石CL图像特征表明所有样品中的锆石主体为岩浆成因, 可以代表花岗岩的形成时代。利用LA-ICP-MS方法对该区花岗质岩石进行了锆石U-Pb定年分析。大部分测点位于谐和线上及附近,江尕勒萨依二长花岗岩的206Pb/238U年龄介于449Ma 458Ma, 加权平均值为453.12.1Ma,锆石U-Pb定年结果表明江尕勒萨依地区花岗岩的形

3、成年龄与超高压岩石的退变质年龄一致，都是折返背景下由地壳物质重熔形成的。关键字:阿尔金；二长花岗岩；LA-ICP-MS锆石定年；Hf同位素特征；碰撞后抬升AbstractAltun mountain is located in the northern margin of the Qinghai Tibet Plateau, the east Qilian Mountains, Kunlun Mountains in the west, is located between the Tarim plate and the Qaidam microplate, occupies a promin

4、ent important tectonic position, the orogenic process time limit to explore contrast of the adjacent geological unit of the connection and the Western tectonic evolution has important geological significance. In this paper, the research on the southern Altyn janggalsay River granite field geology, p

5、etrology, geochemistry and geochronology to determine the spatial distribution characteristics of the study area the early Paleozoic granitoids, magmatism and petrogenesis, combined with regional high-pressure and ultrahigh pressure metamorphism and research results, to explore the South Altun south

6、 margin of janggalsay River granite rocks of diagenetic dynamic background. Discovered by the Altyn janggalsay River granite rock is studied, the main mineral composition of potassium feldspar, plagioclase, quartz and biotite.Which potassium feldspar are euhedral to subhedral crystal, mainly of pert

7、hite and microcline content is 30% 40%, the content of plagioclase between 20% 30%, quartz content is about 30%, biotite content of about 15%, accessory minerals mainly zircon, titanite, apatite and magnetite, High content of SiO2 （7.337% 74.02%, with an average of 73.69%）, TiO2 content （0.11% 0.16%

8、, with an average of 0.13%） low, the CaO content （0.85% 0.94%, with an average of 0.91%） low, Na2O content was 3.04% 3.65%, with an average of 3.32%, K2O content was 5.22% 5.69%, with an average of 5.43%, high total alkali content （K2O+Na2O=8.42 9.01, average 8.76）, a relatively high Na2O K2O conten

9、t, K2O/Na2O=1.46 177, with an average of 1.63. In SiO2-K2O+Na2O diagram all samples fall into the granite area. In SiO2-K2O diagram into high-k calc alkaline potassium shoshonite series, in K2O-Na2O map into high potassic zone has characteristics of rich aluminum, Al2O3 content for 13.78% 13.98%, wi

10、th an average of 13.9%, aluminum clad and index A/CNK=1.03 1.11 in the, with an average of 1.06, aluminous rocks.Janggalsay river is the second longest zircon 176Hf / 177Hf varies in the range of 0.282412 0.282456, with a mean value of 0.282440, epsilon Hf （T） varied from 3.1 1.5, and the mean value

11、 is 2.1, the two stage model ages for 1391Ma 1478Ma, average for 1425Ma. Reflect thesource rocks of thegraniteis mainly fromcrust sourcematerialremelting,its sourceis relativelysingle.Medium （REE = 180.89 ppm janggalsay River monzonitic granite REE 260.17 parts per million （PPM） of is highly enriche

12、d in light rare earth and loss characteristics of heavy rare earth, high ratio between LREE and hree （LR/HR=9.01 22.14, with an average of 20.59）, （LA / Yb） n = 14.18 89.35 average for 74.68, samples were found significant negative Eu anomalies （8eu =0.16 0.36, average for 0.25）. uhedral plagioclase

13、 residual loss from trace elements of primitive mantle normalized spider diagram can be seen, all granite samples are enriched in K, Rb, Th and U and other large ion lithophile elements （LILEs） and light rare earth elements （La, Ce, Nd） and depleted in Nb, Ta, P and Ti and high field strength elemen

14、ts （HFSEs）, with obvious Sr and Ba negative anomalies, Zr, Hf without obvious differentiation, Sr, Ba and negative Eu anomalies show that the partial melting of the source region of the body in the presence of plagioclase or in the magma evolution in the process of fractional crystallization. The area of granite samples of zircon degree as euhedral crystal, a long column shape, length of 100 150 mum, length and width ratio is 2: 1 3: 1. As can be seenfrom the CLimages,showingclearzirconmagmatic oscillatory zoning.A large number