皖北地区五河杂岩温压结构及年代学研究  

The studying of P-T structure and geochronology for Wuhe complex rocks from North Anhui

作　　者：王娟[1] 石永红[1] 宋传中[1] 曹晟[1] 刘奇[1] 庞晓克 

机构地区：[1]合肥工业大学资源与环境工程学院,合肥230009

出　　处：《地质科学》2017年第2期487-505,共19页Chinese Journal of Geology(Scientia Geologica Sinica)

基　　金：国家自然科学基金项目“张八岭隆起变质属性及年代学研究”（编号：4161016）资助.

摘　　要：蚌埠隆起位于华北克拉通南部，胶辽吉造山带的南端，主要由凤阳群和五河杂岩构成。五河杂岩的研究主要集中于年代学以及地球化学领域，其变质P—T条件和地层剖面等研究相对较弱。本文试图从变质岩石学、构造地质学和锆石年代学角度构建朱顶-石门山一线的地壳剖面。通过大量的P-T条件评价，确定了朱顶单元、庄子里单元和石门山单元之间的区别和界限，其中朱顶单元温压结果为低压麻粒岩相：T：720℃-840℃，P=0．90-1．33GPa；庄子里单元温压结果同为低压麻粒岩相，但温度和压力均低于前者：T=700℃-820℃，P=0．50—0．90GPa；石门山单元因岩性限制，仅用白云母Ti温度计拟合计算，结果为低压角闪岩相：T=610℃-700℃，P=0．30—0．50GPa。锆石u—Pb定年获得的变质年龄为2413±22Ma，与前人研究结果基本一致。此外，庄子里地区岩体和磨盘山岩体的锆石u＋Ph年龄晚于2．5—2．4Ga，因此应属于后期侵入岩，计算剖面厚度时要考虑岩体厚度的影响。研究区的岩层产状在45°-60°之间，按照两个极端值计算（不考虑岩体厚度）时获得地壳总厚度为16km，结合3条糜棱岩带的存在，其应属于中．上地壳的物质组成部分。朱顶-石门山-线的地壳剖面，自南向北，以白石山和磨盘山岩体为界，依次为上地壳、中-上地壳和下地壳，温压条件自南向北呈递增趋势。Bengbu uplift located at the south of north craton and existed in south part of Jiao-Liao-Ji orogenic zone, it consist of Fengyang unit and Wuhe unit. Previous studies of Wuhe diamictite mainly direct to chronology and geochemistry, so it metamorphism P-T conditions and stratum profile has rarely attention. The contribution try to build Zhuding-Shimenshan lithosphere profile base on the study of metamorphic petrology, tectonic geology and zircon U-Pb chronology. Conducted large amount of P-T condition calculation we had been confirmed the ambit and thedifference among Zhuding unit, Zhungzili unit and Shimenshan unit. The results of Zhuding unit is LGR and its P-T conditions are as follows： T = 720 ℃ - 840 ℃, P = 0.90 - 1.33 GPa. Zhuangzili unit＇s results similar to former： T = 700 ℃ - 820 ℃, P = 0.50 - 0.90 GPa. The last unit limited by the lithology we just did the P-T conditions calculation with Ti-in-muscovite geothermometer, and the data shows it might be AM facies： T = 610 ℃ - 700 ℃, P = 0.30 - 0.50 GPa. Furthermore, we had attained the zircon U-Pb average age of ZK1013H19 is 2 413± 22 Ma, and it in accord with predecessors studies. Moreover, because of the zircon U-Pb of Mopanshan and Nvshan plutons are later than 2.5 ± 2.4 Ga, they are intrusive rock, so we should take it into consideration when we calculated. And, the attitude of stratum is between 45° and 60°, using two of the extreme stratum to calculate, the thickness of lithosphere is about 16 km. And, taking account of three mylonite belts, we reckon Zhuding-Shimenshan belts belong to mid-upper crust. Summarized the P-T conditions, tectonic geology and zircon U-Pb chronology, the paper built the thinlithosphere profile preliminary. All the results suggest that from south to north are Zhuding unit, Zhuangzili unit and Shimenshan unit, the ambit is Baishishan and Shimoshan pluton respectively. And the P-T conditions show an increasing trend from south to north in Zhuding-Shimenshan belt.

关 键 词：蚌埠隆起 五河杂岩 温压结构 P-T条件 花岗片麻岩 

分 类 号：P588[天文地球—岩石学] P597[天文地球—地质学]