發(fā)布時(shí)間：2018-06-08 22:52

  本文選題：大別超高壓變質(zhì)帶 + 重力-構(gòu)造力復(fù)合壓力�。� 參考：《地學(xué)前緣》2017年02期

【摘要】：研究發(fā)現(xiàn),高壓-超高壓變質(zhì)巖基本都發(fā)育于全球或區(qū)域規(guī)模的大型構(gòu)造帶,產(chǎn)于強(qiáng)烈構(gòu)造變形帶中相對(duì)較弱應(yīng)變的部位。蘇魯—大別超高壓變質(zhì)巖具有明顯的構(gòu)造變形,這成為追索構(gòu)造應(yīng)力-應(yīng)變作用和探討形成構(gòu)造環(huán)境與演化過(guò)程的重要線(xiàn)索。本研究用成巖成礦深度的"構(gòu)造校正測(cè)算方法",進(jìn)行野外觀(guān)察、巖石變形-應(yīng)力測(cè)算及構(gòu)造校正測(cè)算。其結(jié)果顯示,超高壓變質(zhì)巖形成深度在23~55km之間。大別—蘇魯超高壓變質(zhì)巖的鋯石SHRIMP年齡顯示,具有環(huán)帶的內(nèi)核高壓礦物年齡大于680 Ma,而其含柯石英幔圈里超高壓變質(zhì)礦物在(231±4)Ma形成,角閃巖相等退變質(zhì)礦物形成在(211±4)Ma,可見(jiàn)超高壓變質(zhì)發(fā)生在陸緣和陸內(nèi)的地質(zhì)環(huán)境。綜合研究其巖石礦物的Sr-Nd、O和He同位素含量,有力證明了巖石的殼內(nèi)成因特征。深鉆孔巖心的巖石礦物學(xué)系統(tǒng)顯示,超高壓變質(zhì)巖及其幾公里寬范圍里的各類(lèi)圍巖普遍含有柯石英等高壓-超高壓礦物包體。上述實(shí)際資料,用超高壓變質(zhì)的"深俯沖-折返"模式已經(jīng)不能得到科學(xué)的解釋。本文提出大別—蘇魯超高壓變質(zhì)巖"構(gòu)造增壓殼內(nèi)成因模式",認(rèn)為這些超高壓變質(zhì)作用可能發(fā)育在陸內(nèi)地塊之間的強(qiáng)烈構(gòu)造擠壓環(huán)境。在230Ma左右,由于構(gòu)造壓力與重力壓力疊加致使局部達(dá)到超高壓及相應(yīng)溫度等條件,特別是當(dāng)p≥2.8GPa時(shí),變質(zhì)的物理化學(xué)條件得到滿(mǎn)足,可以在23~55km深處發(fā)生超高壓變質(zhì)作用,之后經(jīng)應(yīng)力松弛和拆離構(gòu)造,巖石又逐步抬升并發(fā)生退變質(zhì)作用。也可以說(shuō),該超高壓變質(zhì)巖具有構(gòu)造物理化學(xué)成因。
[Abstract]:It is found that the high-pressure ultrahigh pressure metamorphic rocks are mainly developed in large tectonic zones on a global or regional scale, and occur in the relatively weak strain areas of the strong tectonic deformation zones. The ultrahigh pressure metamorphic rocks of Sulu-Dabie have obvious tectonic deformation, which is an important clue for tracing tectonic stress-strain action and exploring the tectonic environment and evolution process. In this study, the "structural correction method" of diagenetic metallogenic depth was used to carry out field observation, rock deformation-stress calculation and structural correction calculation. The results show that the formation depth of UHP metamorphic rocks is between 23~55km. The zircon shrimp age of the Dabie Sulu ultrahigh pressure metamorphic rocks shows that the core high pressure mineral age of the annular zone is greater than 680 Ma, while the ultrahigh pressure metamorphic minerals in the coesite mantle circle were formed at 231 鹵4 Ma. The equivalent retrograde metamorphic minerals of amphibolite were formed at 211 鹵4 Ma, indicating that the ultrahigh pressure metamorphism occurred in the continental margin and within the continental geological environment. A comprehensive study of the Sr-NdN _ O and he isotopic contents of its rock minerals shows that the genetic characteristics of the rocks in the crust are proved. The petro-mineralogical system of the deep-drilled core shows that the ultrahigh pressure metamorphic rocks and their surrounding rocks in a wide range of several kilometers generally contain high-pressure and ultra-high pressure mineral inclusions such as coesite. The above data can not be explained scientifically by using the "deep subduction-reentrant" model of ultrahigh pressure metamorphism. In this paper, the authors put forward the "genetic model of tectonic pressurized crust" of the Dabie Sulu ultrahigh pressure metamorphic rocks, and considered that these ultrahigh pressure metamorphic processes may have developed in a strong tectonic compression environment between the continental blocks. At 230 Ma or so, the superposition of tectonic pressure and gravity pressure resulted in local ultra-high pressure and corresponding temperature, especially when p 鈮，

本文編號(hào)：1997538