華 天, 李金璽, 李智武, 冉 波, 童 馗, 王自劍, 袁夢(mèng)雨, 蔡鴻燕, 陳 濤, 李 軻, 劉升武

磁化率各向異性與剪切帶

華 天1, 李金璽2*, 李智武1, 冉 波1, 童 馗1, 王自劍1, 袁夢(mèng)雨1, 蔡鴻燕1, 陳 濤1, 李 軻3, 劉升武1

(1.成都理工大學(xué) 油氣藏地質(zhì)及開(kāi)發(fā)工程國(guó)家重點(diǎn)實(shí)驗(yàn)室, 四川 成都 610059; 2.成都理工大學(xué) 地球物理學(xué)院, 地球勘探與信息技術(shù)教育部重點(diǎn)實(shí)驗(yàn)室, 四川 成都 610059; 3.四川省煤田地質(zhì)工程勘察設(shè)計(jì)研究院, 四川 成都 610072)

巖石組構(gòu)記錄了地殼形成與演化的關(guān)鍵信息, 提取這些信息對(duì)分析和恢復(fù)地球動(dòng)力學(xué)過(guò)程具有重要意義。磁化率各向異性(AMS)是一種重要的巖石組構(gòu)方法, 可以有效地揭示巖石的應(yīng)變特征, 分析其地球動(dòng)力學(xué)過(guò)程, 是研究構(gòu)造變形性質(zhì)以及應(yīng)力作用方式的有效手段。本文在梳理AMS的研究歷史、主要成果和最新進(jìn)展的基礎(chǔ)上, 系統(tǒng)闡述了AMS的基本原理以及在剪切帶的應(yīng)用: ①巖石組構(gòu)具有復(fù)雜性, AMS作為一種間接組構(gòu)手段受控于礦物的物理特性、含量以及變形變質(zhì)等多方面因素; ②AMS可以提供剪切帶的運(yùn)動(dòng)學(xué)以及不同部位應(yīng)變狀態(tài)的信息; ③對(duì)于剪切帶, AMS主要受控于磁性礦物(礦物成分和粒度的變化導(dǎo)致全巖磁化率各向異性的變化)、構(gòu)造變形強(qiáng)度(決定磁線理發(fā)展的重要因素)以及流體的作用(流體導(dǎo)致磁性礦物的類型與定向性的變化)。

磁化率各向異性; AMS; 剪切帶; 巖石組構(gòu)

0 引 言

磁性礦物顆粒結(jié)晶方向、形態(tài)和分布的差異導(dǎo)致巖石不同方向上磁化率的差異稱為磁化率各向異性(anisotropy of magnetic susceptibility, AMS), 主要表現(xiàn)為磁晶各向異性和顆粒形狀各向異性兩個(gè)方面(吳漢林, 1988; 許順山和陳柏林, 1998)?？焖?、準(zhǔn)確、適用性強(qiáng)以及無(wú)損性使AMS成為應(yīng)用最廣泛的巖石組構(gòu)方法之一(Tarling and Hrouda, 1993; 潘永信和朱日祥, 1998)。

Voight and Kinoshita (1907)發(fā)現(xiàn)磁性與晶體的取向之間存在對(duì)應(yīng)關(guān)系, 可以通過(guò)磁性的變化識(shí)別晶體的取向。Ising (1942)在研究紋泥磁性時(shí)發(fā)現(xiàn), 平行層面和垂直層面的磁化率存在較大差異, 據(jù)此提出了磁化率各向異性。Graham (1954)指出幾乎所有的巖石都可以觀測(cè)到磁化率各向異性, 磁化率橢球體可以反映巖石內(nèi)部鐵磁性礦物顆粒長(zhǎng)軸的定向分布, 并將其用于地質(zhì)研究。Nye (1957)將磁化率各向異性定義為一個(gè)二階張量。Nagata (1961)根據(jù)張量的不變量性質(zhì), 認(rèn)為磁化率量值橢球體的體積保持不變。至此, 人們才充分認(rèn)識(shí)到主要磁化率軸與非正交晶軸之間的精確關(guān)系。Fuller指出鐵磁性礦物的空間分布對(duì)AMS具有重要意義, 并指出礦物顆粒的定向分布誘發(fā)了磁化率各向異性(Fuller, 1961, 1963)。Owens (1974)進(jìn)一步提出, 相同應(yīng)變狀態(tài)的巖石由于變形過(guò)程的不同會(huì)導(dǎo)致其內(nèi)部鐵磁性礦物分布的差異, 進(jìn)而產(chǎn)生不同的AMS特征。Hrouda and Janák (1976)指出變質(zhì)巖的最小磁化率主軸垂直于變質(zhì)片理, 與巖石的最縮短方向平行。次年, Kligfield et al. (1977)將磁化率各向異性作為應(yīng)變標(biāo)志應(yīng)用于加拿大安大略盆地黏土巖的研究中, 證明了應(yīng)變橢球體的形狀與磁化率橢球體一致, 并且引入了構(gòu)造分析中使用的Flinn圖(Flinn, 1962, 1965)表示磁化率橢球體的形狀。Jelínek (1978)首次將張量統(tǒng)計(jì)方法引入AMS統(tǒng)計(jì)中。20世紀(jì)80年代初, Rathore (1980, 1981)和Kligfield et al. (1982)分別對(duì)英格蘭湖區(qū)板巖和阿爾卑斯地區(qū)灰?guī)r進(jìn)行磁化率各向異性研究, 進(jìn)一步探討了AMS與應(yīng)變的關(guān)系。Hrouda (1982)首次系統(tǒng)歸納了前人的研究, 具有里程碑意義。此外, Borradaile等進(jìn)一步系統(tǒng)的對(duì)磁化率各向異性進(jìn)行綜述(Borradaile and Henry, 1997; Borradaile and Jackson, 2004, 2010)。Parés (2015)綜述了先前變形沉積巖AMS研究。Biederman (2020)對(duì)AMS研究現(xiàn)存挑戰(zhàn)和未來(lái)發(fā)展趨勢(shì)展開(kāi)論述。

有限應(yīng)變和AMS都可以設(shè)想成一個(gè)量值橢球體。但在構(gòu)造地質(zhì)學(xué)研究中, 應(yīng)變橢球體與磁化率橢球體存在較大差別。應(yīng)變橢球體是無(wú)量綱, 軸被歸一化, 橢球體與初始球體具有相同的體積。而AMS橢球體由于樣本的平均磁化率差異, 導(dǎo)致其在形狀(各向異度)和大小上各不相同。因此, 不同樣本的應(yīng)變橢球體是直接可比的, 而AMS橢球體則不行(Borradaile and Jackson, 2010)。大多數(shù)情況下, 磁化率橢球體和應(yīng)變橢球體之間存在較好的相關(guān)性, 二者主軸方向相互平行(Borradaile and Tarling, 1981; Borradaile, 1987, 1988, 1991; Tarling and Hrouda, 1993; Borradaile and Henry, 1997; Parés et al., 1999)。但主軸大小之間沒(méi)有可靠的相關(guān)性(Parés and van der Pluijm, 2004; Borradaile and Jackson, 2010)。

AMS在地質(zhì)學(xué)領(lǐng)域可以廣泛運(yùn)用到以下研究領(lǐng)域: ①研究古流向(Chou et al., 2013; Novak et al., 2014)和古風(fēng)向(Liu and Sun, 2012; Ge et al., 2014); ②恢復(fù)熔巖流向和侵位方向(孫靖鵬等, 2016; Wiegand et al., 2017; Nagaraju and Parashuramulu, 2019); ③揭示不同構(gòu)造背景下應(yīng)變機(jī)制: 前陸等弱變形區(qū)(Soto et al., 2009; Anchuela et al., 2010; Raposo et al., 2014; Dudzisz et al., 2018)、斷裂帶(Abdeen et al., 2014; Dudzisz et al., 2018; Casas-Sainz et al., 2018)以及構(gòu)造疊加變形區(qū)(Mamtani and Sengupta, 2010; Mondal and Mamtani, 2013; Mondal, 2018)。本文就磁化率各向異性的基本原理、其在剪切帶的應(yīng)用情況及最新進(jìn)展進(jìn)行相對(duì)系統(tǒng)的論述。

1 磁化率各向異性的形成機(jī)制

1.1 單礦物磁化率各向異性

磁性礦物是AMS的載體, 準(zhǔn)確識(shí)別磁性礦物是精確解讀AMS所蘊(yùn)含地質(zhì)信息的前提?；诖艑W(xué)性質(zhì)差異, 磁性礦物可分為抗磁性、順磁性、反鐵磁性、鐵磁性以及亞鐵磁性等幾種類型(圖1)。一般來(lái)說(shuō), 巖石的磁化率和各向異性源于所有造巖礦物的貢獻(xiàn), 但具有較高磁化率或各向異性的礦物往往直接控制著整個(gè)巖石的磁化率和各向異性。鐵磁性和亞鐵磁性的磁化率比順磁性礦物的磁化率大三個(gè)數(shù)量級(jí), 對(duì)整個(gè)巖石磁化率的貢獻(xiàn)最大(Hunt et al., 1995)。在不同磁疇狀態(tài)下, 磁性礦物的貢獻(xiàn)也存在一定的差異性(圖2)。對(duì)于多疇顆粒, 磁化率主軸與顆粒的形態(tài)組構(gòu)一致(包括一些順磁性的黑云母和部分角閃石反磁組構(gòu)); 而對(duì)于單疇顆粒, 情況則相反, 出現(xiàn)反磁組構(gòu)現(xiàn)象(Stephenson et al., 1986; Hrouda and Faryad, 2017)。對(duì)超順磁顆粒的研究表明, 在等量條件下超順磁顆粒的磁化率要比穩(wěn)定的單疇和多疇顆粒大得多, 該磁疇狀態(tài)下的磁性顆粒與溫度具有很強(qiáng)的相關(guān)性, 常溫下表現(xiàn)出穩(wěn)定的單疇顆粒所具有的鐵磁性或亞鐵磁性(Henry, 1983; Thompson and Oldfield, 1986)。

單礦物研究表明, 形狀各向異性和磁晶各向異性是主要的控制因素。形狀各向異性受限于強(qiáng)磁性礦物, 主要為磁鐵礦。當(dāng)固有磁化率較低時(shí), 由形狀引起的磁各向異性則很小。理論計(jì)算表明, 當(dāng)固有磁化率的值為4π×10–2SI時(shí), 形狀各向異性最大為1.06, 如磁鐵礦(Stacey et al., 1960; Bhathal, 1971)。對(duì)于一些晶體而言, 磁化傾向于沿著某些晶軸, 這種效應(yīng)稱為磁晶各向異性。磁黃鐵礦的磁晶各向異性很大, 掩蓋了靜磁各向異性, 此時(shí)形狀各向異性的影響可以忽略。對(duì)于一些常見(jiàn)的順磁性礦物(如普通輝石、角閃石), 雖然磁化率較低, 但磁化率各向異性卻較高。普通輝石的各向異性值在1.2~1.4之間, 平均值為1.26; 普通角閃石在1.08~1.30之間, 平均值為1.25(Uyeda et al., 1963; Bhathal, 1971)。

1.2 全巖磁化率各向異性

由于巖石內(nèi)部不同礦物顆粒的形狀、排列、空間分布、以及磁晶各向異性等因素的影響導(dǎo)致整體磁化率表現(xiàn)為各向異性。當(dāng)全巖的磁化率值較高時(shí), 不同磁化率主軸值往往會(huì)出現(xiàn)較大的差異。全巖磁化率各向異性成因主要有以下六點(diǎn): ①礦物顆粒的形狀各向異性。一個(gè)非等軸磁性顆粒在不同方向上有不同的退磁系數(shù), 此時(shí)磁化率各向異性與礦物顆粒的形狀有關(guān); ②礦物晶體的磁晶各向異性。對(duì)一些晶體而言, 磁化傾向于沿著某些晶體軸。當(dāng)巖石中主要磁性礦物為鐵磁性的磁黃鐵礦以及含鐵的硅酸鹽礦物時(shí), 磁晶各向異性占據(jù)優(yōu)勢(shì); 當(dāng)主要磁性礦物為磁鐵礦或鈦磁鐵礦時(shí), 形狀各向異性占據(jù)優(yōu)勢(shì)(Jackson, 1991; Raposo et al., 2008); ③磁疇排列的各向異性。任何一種鐵磁性或亞鐵磁性材料的固有磁化率是對(duì)其施加的磁場(chǎng)方向與磁疇方向的函數(shù); ④磁性顆粒排列引起的磁各向異性。當(dāng)巖石中包含數(shù)量眾多的磁鐵礦時(shí), 此現(xiàn)象尤為明顯。Grabovsky and Bradskaya (1958)將其定義為: “結(jié)構(gòu)”磁各向異性。即由相互作用的磁性顆粒的平面分布或線狀分布造成。20世紀(jì)60年代, Stacey在巴黎通過(guò)實(shí)驗(yàn)證實(shí)結(jié)構(gòu)磁各向異性是由前二者中的某一個(gè)或者同時(shí)作用所造成的; ⑤交換各向異性(最初用來(lái)定義亞鐵磁性和反鐵磁性物質(zhì)二者之間相互作用的性質(zhì)。之后的研究表明, 在鐵磁性和亞鐵磁性物質(zhì)之間也存在這種性質(zhì)。當(dāng)溫度或磁場(chǎng)方向發(fā)生變化, 相應(yīng)的磁滯回線會(huì)發(fā)生位移)(Bhathal, 1971); ⑥應(yīng)力誘發(fā)的各向異性。它與磁致伸縮有關(guān), 為磁化強(qiáng)度與晶軸方向的函數(shù)(Bhathal, 1971; Jackson, 1991)。

M. 磁化強(qiáng)度; H. 磁場(chǎng)強(qiáng)度; T. 絕對(duì)溫度; Tc. 居里溫度; Tn. 尼爾溫度; Ta. 漸進(jìn)溫度; Tp. 臨界溫度。

(a) 磁疇分區(qū)(據(jù)Thompson and ?ldfield, 1986); (b) 磁晶各向異性(據(jù)袁學(xué)誠(chéng), 1991); (c) 多晶樣品內(nèi)磁疇的排列情況(據(jù)Thompson and ?ldfield, 1986); (d) 幾類單疇磁化曲線(據(jù)Thompson and ?ldfield, 1986)。

2 磁化率各向異性與剪切帶

剪切帶是面狀高剪切應(yīng)變帶, 具有不同類型和形成機(jī)制, 反映了大陸巖石圈變形行為。據(jù)變形機(jī)制、變形行為以及發(fā)育的物理環(huán)境可分為: 脆性剪切帶(斷層和斷裂帶)、韌?脆性過(guò)渡型剪切帶以及韌性剪切帶(Rasmay, 1980)。開(kāi)展剪切帶磁化率各向異性的研究, 可以在顯微組構(gòu)分析等的基礎(chǔ)上進(jìn)一步約束其運(yùn)動(dòng)學(xué)特征和變形機(jī)制(Ziegler, 1989; Kley and Voigt, 2008; Solum and Pluijm, 2009; Levi and Weinberger, 2011; Abdeen et al., 2014; Casas-Sainz et al., 2017; 王開(kāi)等, 2017; 陳應(yīng)濤等, 2019)。

2.1 脆性斷層

脆性斷層是地殼淺層次脆性變形的產(chǎn)物, 具有一個(gè)或多個(gè)清楚的不連續(xù)界面(曾佐勛等, 2008)。Casas-Sainz et al. (2017)對(duì)Cameros-Demanda逆沖斷層的研究表明, 磁線理可以揭示斷層的傳播方向, 但斷層不同部位存在差異性(平行或垂直傳播方向)。當(dāng)所采集的數(shù)據(jù)不足以產(chǎn)生強(qiáng)烈的簇狀分布時(shí), 磁線理的可靠性則降低。當(dāng)鐵磁性礦物含量增加時(shí), 磁線理的可靠性則提高。此外, 他們認(rèn)為變形強(qiáng)烈地區(qū)的磁組構(gòu)不受大規(guī)模流體或深部成巖作用的影響。Braun et al. (2015)對(duì)死海西邊界正斷層的研究顯示, 斷層面處磁化率各向異度值較高。斷層面處磁組構(gòu)的定向性與斷層活動(dòng)所產(chǎn)生的局部應(yīng)變相關(guān)。斷層內(nèi)應(yīng)力場(chǎng)的局部差異性會(huì)導(dǎo)致磁化率橢球體發(fā)生偏轉(zhuǎn)。隨著黏土礦物的產(chǎn)生, 局部應(yīng)變可能被放大(Medina-Cascales et al., 2019)。剪切應(yīng)變的強(qiáng)度直接影響磁線理的類型(Marcén et al., 2020)。Nakamura and Nagahama (2001)研究發(fā)現(xiàn), 弱碎裂化花崗巖處磁線理與破裂面的定向性近一致, 而強(qiáng)碎裂化花崗巖內(nèi)由于綠泥石化的黑云母發(fā)生強(qiáng)烈擠壓破碎, 導(dǎo)致磁線理的定向性與破裂面存在較大差異, 并且出現(xiàn)磁化率各向異度較低甚至各向同性的情況。Román- Berdiel et al. (2019)在對(duì)Rastraculos斷裂帶斷層巖的研究中指出, 影響斷層巖磁組構(gòu)類型的主要因素是磁性礦物, 而不是露頭尺度的構(gòu)造變形強(qiáng)度。

2.1.1 增生楔部位磁組構(gòu)

增生楔又稱增生柱或增生雜巖, 是大洋板塊沿海溝俯沖時(shí), 被刮削下來(lái)的沉積蓋層和洋殼碎片與原地沉積物堆積到海溝的向陸方向形成的楔形地質(zhì)體(Stern, 2005)。增生楔內(nèi)部應(yīng)力分布具有差異性, 而磁組構(gòu)可以有效識(shí)別應(yīng)力的變化(Lin et al., 2010; Kanamatsu et al., 2012)?；摂鄬臃指盍藦?qiáng)變形部位和弱/未變形部位(Moore, 1989)?；搶由舷聟^(qū)域磁組構(gòu)類型存在差異?；搶酉虏看沤M構(gòu)呈典型的沉積組構(gòu)(Owens, 1993), 且磁化率各向異度值較低, 可能是由于隨著流體壓力的增高, 沉積物壓實(shí)作用減弱甚至停止所導(dǎo)致(Yang et al., 2013)?；搶由喜看呕蕶E球體朝扁長(zhǎng)形轉(zhuǎn)變, 各主軸簇狀分布明顯(Owens, 1993), 磁線理垂直于板塊俯沖方向(Yang et al., 2013)。增生楔內(nèi)各向異性參數(shù)的差異性, 可能暗示其局部變形強(qiáng)度的差異性(Owens, 1993), 也可能反應(yīng)泥質(zhì)雜基中砂級(jí)碎屑含量的差異性(Ujie et al., 2000)。Kanamatsu et al. (2012)利用磁組構(gòu)對(duì)Nankai Trough處增生楔內(nèi)應(yīng)變隨時(shí)間和空間的變化展開(kāi)研究發(fā)現(xiàn), 鉆井 C0001處, 增生楔內(nèi)(C1U2)磁化率橢球體以扁長(zhǎng)形為主, 是增生過(guò)程中平行層縮短所導(dǎo)致(Hrouda et al., 2009)。鉆井C0002處(Kumano弧前盆地處)增生楔內(nèi)磁化率橢球體趨于扁長(zhǎng)形, 是受后期板塊俯沖產(chǎn)生的側(cè)向擠壓力疊加改造的結(jié)果, 但擠壓強(qiáng)度相對(duì)較弱(Ujiie et al., 2003)。磁組構(gòu)指示NW-SE向擠壓變形, 與現(xiàn)今NE-SW向最大水平主應(yīng)力正交。應(yīng)力方向的差異性暗示現(xiàn)今構(gòu)造應(yīng)力場(chǎng)未對(duì)其造成影響(Kanamatsu et al., 2012)。

2.1.2 斷層巖磁組構(gòu)

斷層巖是斷層帶局部應(yīng)力變化的產(chǎn)物(Sibson, 1977; Wise et al., 1984)。其中淺層次斷層巖主要包括: 斷層泥、碎裂巖以及斷層角礫巖。其中斷層泥是斷層剪切滑動(dòng)、碎裂、碾磨和黏土礦化作用的產(chǎn)物, 記錄了斷層活動(dòng)的信息(Sibson, 1977)。相較圍巖, 斷層泥含有更多的順磁性礦物(Solum and van der Pluijm, 2009)。Carboneras斷層帶內(nèi)斷層泥磁組構(gòu)最小磁化率主軸垂直于斷層面, 磁線理與斷層走向平行。磁化率各向異度在斷層泥處最低, 表明斷層泥處組構(gòu)發(fā)育程度較低(Solum and van der Pluijm, 2009)。對(duì)臺(tái)灣車籠埔斷裂帶的磁組構(gòu)研究發(fā)現(xiàn), 斷層泥具有較高的磁化率各向異度, 磁化率橢球體主要為扁平狀, 磁組構(gòu)與區(qū)域應(yīng)力狀態(tài)相關(guān)(Yeh et al., 2007)。對(duì)英國(guó)安格爾西島北部沿海Porth-pisty11斷層泥磁組構(gòu)研究表明, 磁組構(gòu)的定向性與斷層運(yùn)動(dòng)方向一致(Hailwood et al., 1992)。然而, 來(lái)自臺(tái)灣車籠埔斷層科鉆(TCDP-Hole B)所取得斷層泥的AMS顯示: 主滑動(dòng)帶(principal slip zone, PSZ)處磁面理和磁化率各向異度值最低, 可能受控于斷層活動(dòng)中高溫和流體的作用; 而斷層泥處磁面理和磁化率各向異度值則最高, 與熱流體作用新生的針鐵礦的分布有關(guān); 地表露頭處, 從巖墻到斷層泥磁線理呈下降趨勢(shì), 而磁面理和磁化率各向異度值先增加后減小(Chou et al., 2014)。Nakamura and Nagahama (2001)對(duì)斷層泥的研究也顯示斷層泥處磁化率值較高而磁化率各向異度較低, 他們認(rèn)為, 斷層泥處含鐵氧化物的生長(zhǎng)使硅酸鹽礦物沿面理面的定向分布推遲。綜上, 脆性斷層巖處AMS可能受控于應(yīng)力變化也可能受后期熱化學(xué)反應(yīng)等的影響。在確定是否存在次生礦物的基礎(chǔ)上對(duì)其進(jìn)行解釋, 可能更可靠(Román- Berdiel et al., 2019; Yang et al., 2020)。

近年來(lái)通過(guò)大量科學(xué)鉆探, 對(duì)斷層巖(泥)磁學(xué)性質(zhì)的認(rèn)識(shí)取得了較大進(jìn)展。如對(duì)臺(tái)灣車籠埔斷層的科鉆研究發(fā)現(xiàn), 1194 m和1243 m處發(fā)育的假玄武玻璃具有較高的磁化率值, 可能與順磁性礦物熱解為鐵磁性礦物(Mishima et al., 2006)或鐵磁性礦物的碾磨細(xì)化有關(guān)。研究表明, 鐵磁性礦物顆粒在剪切作用下細(xì)化為超順磁狀態(tài)可以引起磁化率的增加(張蕾等, 2018)。高分辨率磁化率測(cè)量揭示斷層泥處磁化率值出現(xiàn)波動(dòng)(Hirono et al., 2006)。由于摩擦加熱(>400 ℃), 順磁性含鐵礦物熱解為磁鐵礦, 從而導(dǎo)致黑色斷層泥處磁化率值升高(Mishima et al., 2009)。高速摩擦實(shí)驗(yàn)表明, 短時(shí)間內(nèi)的摩擦加熱也會(huì)導(dǎo)致磁化率的變化(Tanikawa et al., 2007)。汶川科鉆同樣發(fā)現(xiàn)斷層泥和假玄武玻璃具有高磁化率的現(xiàn)象(Pei et al., 2010, 2014; 張蕾等, 2017, 2018)。實(shí)驗(yàn)揭示, 當(dāng)摩擦加熱溫度達(dá)1300 ℃, 含鐵礦物就會(huì)發(fā)生還原反應(yīng), 從而生成大量單質(zhì)鐵球粒, 引起假玄武玻璃的高磁異?，F(xiàn)象(Zhang et al., 2018; 張蕾等, 2019)。與之相反, 在針對(duì)安縣?灌縣斷裂帶的科鉆(何祥麗等, 2018)以及九龍?zhí)讲?Liu et al., 2014)和北川?映秀斷裂帶的大溝探槽(Yang et al., 2012a)等的研究中出現(xiàn)斷層泥處磁化率低于圍巖的現(xiàn)象, 原因可能是: ①斷層泥所經(jīng)歷的溫度未超過(guò)300~400 ℃(Gillett, 2003; Yang et al., 2012b; Liu et al., 2014); ②當(dāng)斷層處于蠕滑變形時(shí), 在流體的作用下, 水巖反應(yīng)導(dǎo)致鐵磁性礦物轉(zhuǎn)變?yōu)轫槾判缘V物(Kuo et al., 2012; Liu et al., 2014; 何祥麗等, 2018)(圖3)。

2.2 韌性剪切帶

Rathore and Becke (1980)對(duì)阿爾卑斯造山帶中Periadriatic Line (P.L.)剪切帶的AMS研究發(fā)現(xiàn), 磁化率橢球體以扁圓形(Oblate)為主。最小磁化率主軸方向與云母C軸具有很好的一致性。利用AMS可以對(duì)剪切帶建立分段運(yùn)動(dòng)模型。Hrouda (1982)指出磁面理、磁線理的分布與構(gòu)造片理和線理具有一致性。Goldstein and Brown (1988)對(duì)阿巴拉契亞山脈南部Brevard剪切帶的AMS研究發(fā)現(xiàn), 磁化率橢球體以壓扁形為主。糜棱巖化伴隨著磁化率的降低。磁化率各向異性可以定性的描述糜棱巖的應(yīng)變歷史。隨后, Mims et al. (1990)對(duì)北卡羅萊納州Nutbush Creek韌性剪切帶研究后指出, AMS可以用來(lái)估算韌性剪切帶應(yīng)變場(chǎng)的大小, 但不能估算剪切帶內(nèi)的應(yīng)變歷史或應(yīng)力大小。Kankeu et al. (2009)在喀麥隆東部Bétaré-Oya剪切帶, 利用磁化率橢球體形態(tài)、磁線理和磁面理產(chǎn)狀識(shí)確定了三期構(gòu)造變形, 并繪制出了區(qū)域上的磁線理分布跡線。Ferré et al. (2014)對(duì)韌性剪切帶內(nèi)AMS特征進(jìn)行了系統(tǒng)綜述, 并指出剪切帶內(nèi)AMS與應(yīng)變的關(guān)系不僅取決于磁性礦物的類型也取決于變形機(jī)制。Vikas et al. (2016)利用AMS和巖組學(xué)對(duì)印度南部Achankovil剪切帶開(kāi)展運(yùn)動(dòng)學(xué)和顯微構(gòu)造演化研究。研究表明, 礦物晶格優(yōu)選方向(LPO)指示剪切帶內(nèi)塑性變形主要通過(guò)晶內(nèi)滑移完成, 剪切帶的再活化造成先存組構(gòu)的改變。AMS與LPO具有一致性, 反映了區(qū)域上應(yīng)力/運(yùn)動(dòng)學(xué)與巖石內(nèi)組構(gòu)演化的關(guān)系。Marcén et al. (2018)通過(guò)對(duì)比比利牛斯Gavarnie剪切帶內(nèi)顯微構(gòu)造與磁化率橢球體, 確定了剪切帶內(nèi)部應(yīng)力分布和運(yùn)移方向。

圖3 圖示巖石碎裂化過(guò)程中流體的作用(據(jù)Yang et al., 2016)

相較國(guó)外, 國(guó)內(nèi)學(xué)者利用AMS對(duì)剪切帶也開(kāi)展了大量的研究工作。施建寧等(1990)對(duì)閩浙碰撞造山帶內(nèi)部韌性剪切帶展開(kāi)研究發(fā)現(xiàn): 磁化率橢球體以壓扁形為主; 磁面理較磁線理發(fā)育; 最小磁化率主軸與巖石片理法線的產(chǎn)狀基本一致; 剪切帶中隨著深度的增加, 由簡(jiǎn)單剪切作用向純剪作用轉(zhuǎn)變, 面狀構(gòu)造的發(fā)育不斷增強(qiáng)。Zhou et al. (2002)對(duì)哀牢山?紅河韌性剪切帶展開(kāi)AMS研究, 具體分析了剪切帶內(nèi)外的構(gòu)造變形性質(zhì)。楊朝斌等(2006)認(rèn)為磁化率各向異度()直接反映韌性變形的強(qiáng)度。他們利用磁面理對(duì)剪切帶進(jìn)行運(yùn)動(dòng)學(xué)研究, 指出雅魯藏布江縫合帶內(nèi)部的兩條韌性剪切帶以逆沖為主, 兼具右旋扭動(dòng)的運(yùn)動(dòng)學(xué)特征。AMS主要反映較強(qiáng)的壓縮作用, 而非簡(jiǎn)單剪切作用。陳柏林等(2007)指出后期熱事件會(huì)導(dǎo)致剪切帶內(nèi)AMS的均一化, 出現(xiàn)值降低甚至消失的現(xiàn)象。此外, 巖性和應(yīng)力的變化也可能引起AMS的變化。用值來(lái)判別構(gòu)造變形強(qiáng)度可能更適用于相似巖性的樣品(梁文天等, 2008)。李陽(yáng)等(2017)利用AMS、顯微組構(gòu)和運(yùn)動(dòng)學(xué)渦度對(duì)秦嶺沙溝街韌性剪切帶進(jìn)行研究, 發(fā)現(xiàn)剪切帶內(nèi)部整體各向異度值較大(均>1.19, 最高可達(dá)2.41), 表明構(gòu)造變形較為強(qiáng)烈。磁化率橢球體以壓扁形為主。磁線/面理與礦物線/面理產(chǎn)狀較為一致。結(jié)合邊界斷層和C面理產(chǎn)狀, 認(rèn)為剪切帶具有左行走滑擠壓的運(yùn)動(dòng)學(xué)特征。同時(shí), 運(yùn)動(dòng)學(xué)渦度研究表明, 剪切帶中純剪切作用所占的比重大于簡(jiǎn)單剪切作用。上述研究表明, ①磁化率橢球體的形狀可以反映巖石變形的性質(zhì)(拉伸、壓縮或剪切); ②磁化率各向異度能夠反映韌性變形的強(qiáng)度。但巖性的差異、后期熱事件以及應(yīng)力的變化會(huì)引起值的變化; ③磁面理、磁線理和最小磁化率主軸的產(chǎn)狀可以用來(lái)分析剪切帶的運(yùn)動(dòng)方向。

2.2.1 韌性剪切帶內(nèi)面理與線理的研究

Berthé et al. (1979)在研究法國(guó)South Armorican韌性剪切帶內(nèi)面理構(gòu)造時(shí)提出S-C組構(gòu)(S-C fabrics)。他把一組平行剪切帶邊界的面理稱為C面理, 把另一組平行變形礦物優(yōu)選方向的面理稱為S面理, 二者組合稱為S-C組構(gòu)(圖4)。顯微構(gòu)造上, C面理為間隔排列的含有細(xì)小重結(jié)晶顆粒強(qiáng)剪切應(yīng)變帶。其內(nèi)石英顆粒動(dòng)態(tài)重結(jié)晶, 形成大致平行于S面理的傾斜組構(gòu)。云母發(fā)生強(qiáng)烈變形和細(xì)?；?。由于較強(qiáng)的剪切應(yīng)變, C面理表面形成類似于擦痕鏡面的形態(tài)且發(fā)育“槽中脊”型擦痕(Lc)(Lin and Williams, 1992)。S面理由C面理之間先存礦物的形狀優(yōu)選定向所決定(Simpson and Schmid, 1983)。一般為層狀硅酸鹽、石英或長(zhǎng)石等細(xì)小顆粒(Dell’Angelo and Tullis, 1989)。C面理相較S面理更離散但也更連續(xù)(Lin et al., 2007)。Berthé et al. (1979)認(rèn)為S面理與C面理同時(shí)形成。Lister and Snoke (1984)認(rèn)為S面理與C面理分別形成于兩期構(gòu)造事件。Lin and Williams (1992)認(rèn)為以下兩點(diǎn)對(duì)解釋S-C組構(gòu)的形成機(jī)制極為重要: ①形成S-C組構(gòu)的糜棱巖表現(xiàn)為韌性變形, 圍壓對(duì)變形機(jī)制起到制約作用; ②晶粒級(jí)別的變形是不均勻的。

韌性剪切帶內(nèi)還發(fā)育C′面理(伸展褶劈理), 是以塑性剪切(Platt and Vissers, 1980)或脆性不連續(xù)為特征的面狀構(gòu)造。該面理與剪切帶邊界斜交, 與C面理夾角一般小于30°。與S-C組構(gòu)共同組成S-C-C′復(fù)合組構(gòu)(Lister and Snoke, 1984)。C′面理常以剪切面或狹窄剪切帶的方式切割S面理(劉江, 2019)。內(nèi)部可見(jiàn)強(qiáng)烈重結(jié)晶的細(xì)小石英顆粒(Law et al., 1984)。C′面理在低剪切應(yīng)變下發(fā)育良好。隨著剪切應(yīng)變的增加, C′面理逐漸旋轉(zhuǎn)至剪切邊界或因重結(jié)晶加劇導(dǎo)致C′面理逐漸消失(Dell’Angelo and Tullis, 1989)。剪切帶有時(shí)發(fā)育共軛的伸展褶劈理, 二者發(fā)育情況存在差異(Law et al., 1984)。Biot (1965)認(rèn)為各向異性材料在變形過(guò)程中存在擾動(dòng), 而變形誘發(fā)的顯微構(gòu)造變化可能是形成C′的關(guān)鍵(Platt and Vissers, 1980)。White et al. (1980)認(rèn)為伸展褶劈理是先存較發(fā)育面理后期破裂的產(chǎn)物, 是韌性剪切帶晚期次生劈理。C′可能與剪切帶非均勻變形有關(guān)(Behrmann, 1987)。Behrmann (1987)指出對(duì)于強(qiáng)各向異性的巖石, 多組共軛伸展褶劈理的形成可能受控于機(jī)械作用而非運(yùn)動(dòng)學(xué)因素。

除面理外, 韌性剪切帶內(nèi)還主要發(fā)育兩類線理: “槽中脊”型擦痕(Lc)(Means, 1987)和拉伸線理(Ls)(許志琴, 1989)(圖4)。Lc常發(fā)育在C面理上, 平行于剪切運(yùn)動(dòng)方向。若未受到后期改造, Lc可給出可靠的運(yùn)動(dòng)學(xué)信息(Lin et al., 2007)。隨著變形的增強(qiáng), Lc的脊(ridge)和槽(groove)變長(zhǎng)和變淺(Lin and Williams, 1992a)。Ls位于S面理上(除真正的L構(gòu)造巖: 只發(fā)育拉伸線理, 面理發(fā)育較弱或不發(fā)育)(林壽發(fā)等, 2007)。研究發(fā)現(xiàn)剪切帶內(nèi)Ls方位會(huì)因以下原因發(fā)生變化: ①單剪局部化, 純剪趨向于廣泛分布(Gordon, 1995; Lin and Jiang, 1998); ②應(yīng)變量的變化(Lin and Williams, 1992); ③角的變化(簡(jiǎn)單剪切方向與純剪切主分量方向的夾角(Jiang and Williams, 1998)。對(duì)于高剪切應(yīng)變帶, 拉伸線理方向與剪切方向之間不存在簡(jiǎn)單的關(guān)系。因此, 很難用拉伸線理的方向來(lái)推斷剪切方向, 除非剪切帶的運(yùn)動(dòng)學(xué)格架為單斜對(duì)稱, 即拉伸線理在剪切帶邊界上的正交投影平行于剪切方向(Lin and Williams, 1992b; Lin et al., 2007; 林壽發(fā)等, 2007)。

(a) 韌性剪切帶(右行剪切下)C′與S面理與C面理幾何關(guān)系示意圖(據(jù)Blenkinsop and Treloar, 1995); (b) 典型S-C糜棱巖構(gòu)造簡(jiǎn)圖。C面理平行剪切帶邊界, 沿C面的剝露面擦痕面, C面上槽中脊型擦痕平行于剪切方向, 拉伸線理發(fā)育在S面理上(據(jù)李陽(yáng)等, 1992a修改); (c) 磁面理分布跡線(據(jù)Lin et al., 2009修改); (d) 共軛伸展褶劈理與S面理和線理幾何關(guān)系示意圖(據(jù)劉江, 2019修改)。

2.2.2 S-C(C′)組構(gòu)與AMS

Aranguren et al. (1996)對(duì)S-C糜棱巖中AMS的研究表明, AMS同時(shí)受控于S面理和C面理, 主要反映了兩個(gè)形狀各向異性的面狀組構(gòu)的疊加效應(yīng)。磁面理處于S面理和C面理的中間位置。隨著剪切應(yīng)變量的增大, 磁面理逐漸平行于C面理。磁線理垂直于S面理和C面理的交線, 近平行于拉伸線理, 與剪切運(yùn)動(dòng)方向一致。Tomezzoli et al. (2003)將S-C組構(gòu)與AMS對(duì)比后發(fā)現(xiàn), 磁面理偏離S面理約20°, 可能是由于S-C組構(gòu)產(chǎn)生的疊加組構(gòu)所導(dǎo)致。Ono et al. (2010)利用背散射電子圖像分析技術(shù)對(duì)磁組構(gòu)和S-C-C′關(guān)系展開(kāi)研究, 發(fā)現(xiàn)磁組構(gòu)主要反映了順磁性單斜礦物特別是黑云母顆粒的形狀優(yōu)先定向。磁面理處于S面和C面的中間位置。磁線理平行于S面理和C面理的交線。Casas-Sainz et al. (2018)將Daroca剪切帶內(nèi)S-C組構(gòu)與AMS進(jìn)行對(duì)比后發(fā)現(xiàn), 磁面理存在平行S面理或C面理的現(xiàn)象, 表明剪切面內(nèi)層狀硅酸鹽礦物的重新定向或鐵磁性礦物的富集影響了磁面理的定向性。受變形強(qiáng)度和礦物學(xué)控制, 磁線理平行于S面理和C面理的交線。Marcén et al. (2018)對(duì)比利牛斯Gavarnie剪切帶內(nèi)S-C-C′組構(gòu)與AMS的研究發(fā)現(xiàn), 磁面理存在三種定向性: ①平行于S面理; ②平行于C面理; ③平行于C′面理。磁線理具有兩種定向性: ①與剪切運(yùn)動(dòng)方向一致; ②與剪切運(yùn)動(dòng)方向垂直。與剪切運(yùn)動(dòng)方向一致的磁線理受控于阿爾卑斯韌性變形構(gòu)造。與剪切運(yùn)動(dòng)方向垂直的磁線理形成于早期華力西運(yùn)動(dòng), 且未被后期變形改造。對(duì)磁線理來(lái)說(shuō), 當(dāng)主要受順磁性礦物控制時(shí), 在變形早期, 磁線理表現(xiàn)為平行于S面理和C面理的交線。在更高級(jí)的變形階段, 則表現(xiàn)為垂直于S面理和C面理的交線, 平行于剪切運(yùn)動(dòng)方向。當(dāng)磁線理主要受控于鐵磁性礦物時(shí), 磁線理普遍表現(xiàn)為平行于剪切運(yùn)動(dòng)方向(Casas-Sainz et al., 2018)。

3 變形機(jī)制與磁組構(gòu)

前人對(duì)剪切帶內(nèi)變形機(jī)制與磁組構(gòu)的關(guān)系開(kāi)展了大量研究。Borradaile and Alford (1987)通過(guò)實(shí)驗(yàn)發(fā)現(xiàn), 磁化率各向異性的變化與應(yīng)變具有很強(qiáng)的相關(guān)性。構(gòu)造變形強(qiáng)度是決定磁線理發(fā)展的重要因素(Parés and van der Pluijm, 2002)。但是, Bikramaditya et al. (2017)對(duì)三期疊加變形片麻巖的研究表明, 磁組構(gòu)結(jié)果與區(qū)域上優(yōu)勢(shì)面理(第二期變形事件)不一致, 主要反應(yīng)了最后一期弱變形事件。剪切帶內(nèi)位錯(cuò)滑移、位錯(cuò)蠕變和擴(kuò)散蠕變等變形機(jī)制引起磁性礦物的重新定向和晶體內(nèi)部的變形, 導(dǎo)致磁化率各向異性的改變(Jackson et al., 1993; Ferré and Améglio, 2000; One et al., 2010; Till and Moskowitz, 2014; Ferré et al., 2014)。相較純剪, 簡(jiǎn)單剪切更能引起磁化率各向異性的變化(Borradaile and Alford, 1988)。剪切過(guò)程中, 鐵磁性礦物粒度的減小可以誘發(fā)磁化率(Billi, 2005; Sammos and Ben-Zion, 2008)和各向異度的變化(Jackson et al., 1993)。Yang et al. (2020)認(rèn)為磁性礦物粒度的減小可能是造成日本Nojima斷層處強(qiáng)碎裂花崗巖出現(xiàn)弱磁化率各向異性, 甚至各向同性的原因。

Parés and van der Pluijm (2002)認(rèn)為磁性礦物的變化是影響磁化率各向異性的另一因素。高磁化率礦物含量的變化會(huì)引起磁化率各向異性較大的變化(Borradaile, 1988)。研究發(fā)現(xiàn), 剪切帶內(nèi)由摩擦導(dǎo)致的熱化學(xué)變化可以誘發(fā)含鐵礦物的分解和轉(zhuǎn)化, 形成磁鐵礦等鐵磁性礦物(Yang et al., 2019)。菱鐵礦在400~580 ℃時(shí)可分解為磁鐵礦(Koziol, 2004; Han et al., 2007); 纖鐵礦在200 ℃左右會(huì)轉(zhuǎn)變?yōu)榇懦噼F礦, 進(jìn)一步在300~350 ℃轉(zhuǎn)變?yōu)槌噼F礦(Gehring and Hofmeister, 1994)。

剪切帶內(nèi)存在大量流體(劉貴, 2020)。一方面, 構(gòu)造運(yùn)動(dòng)可以對(duì)流體的運(yùn)移和循環(huán)造成影響(Sibson and Scott, 1998; Robl et al., 2004)。對(duì)哀牢山韌性剪切帶型金礦的研究表明, 強(qiáng)烈的構(gòu)造變動(dòng)形成的混合流體與已糜棱巖化的圍巖發(fā)生水?巖反應(yīng), 導(dǎo)致成礦流體物理化學(xué)條件的改變和礦物的沉淀(孫曉明等, 2007)。對(duì)夾皮溝金礦的研究同樣表明由構(gòu)造誘發(fā)的高壓流體導(dǎo)致大氣降水、變質(zhì)水和巖漿流體混合, 含礦流體的失衡導(dǎo)致礦石的沉淀(Deng et al., 2009)。流體使含鐵礦物發(fā)生溶解, 從中析出Fe2+(Humbert et al., 2012; Yang et al., 2016)。富含F(xiàn)e2+的流體一方面被認(rèn)為是新生鐵磁性礦物的物質(zhì)來(lái)源(Pechersky and Genshaft, 2001)。另一方面被認(rèn)為是形成含鐵黏土礦物(如綠泥石)的來(lái)源。并且隨著流體與斷層活動(dòng)的繼續(xù), 更多的順磁性含鐵蝕變礦物出現(xiàn)在新生的斷層巖中(Yang et al., 2016), 從而導(dǎo)致剪切帶內(nèi)磁化率及各向異性的變化(Yang et al., 2020)。Yang et al. (2020)指出, 新生礦物的磁化率各向異性可能并非與應(yīng)變相聯(lián)系。Saint-Bezar et al. (2002)研究顯示, 平行于構(gòu)造縮短方向磁線理的出現(xiàn), 可能和富鐵礦脈與層面的相交有關(guān)。磁組構(gòu)的幾何形態(tài)與定向性也可能受控于熱液蝕變作用(Just et al., 2004)。地震發(fā)生兩年后, 斷層的性質(zhì)就會(huì)因流體的作用發(fā)生顯著變化(Brodsky et al., 2009)。此外, 這些新生成的磁性礦物可能形成于不同的斷層運(yùn)動(dòng)階段(事件), 并且具有不同的形成方式, 所以磁組構(gòu)所記錄的信息也可能不同(Yang et al., 2020)。對(duì)死海斷層白堊樣品的分離研究表明, 其中順磁性黏土礦物保留初始沉積組構(gòu), 而抗磁性方解石則體現(xiàn)為構(gòu)造組構(gòu)(Issachar et al., 2018)。另一方面, 流體反作用于構(gòu)造活動(dòng), 影響其發(fā)生、發(fā)展。段寶慶(2015)對(duì)龍門山斷裂花崗巖質(zhì)破裂帶的研究表明, 流體不僅會(huì)因封閉產(chǎn)生的高壓使斷層弱化, 也會(huì)與圍巖反應(yīng)生成摩擦系數(shù)低的黏土等層狀硅酸鹽礦物。礦物成分和粒度的變化導(dǎo)致全巖磁化率各向異性的變化, 并隨著構(gòu)造運(yùn)動(dòng)的持續(xù), 磁化率各向異性可能會(huì)持續(xù)變化(Ferré et al., 2014)。

4 結(jié) 論

全巖磁化率各向異性是磁性礦物類型、含量、大小以及分布等的綜合反映, 受到其形成時(shí)(后)各種地質(zhì)因素控制。但利用AMS可以在剪切帶獲得常規(guī)地質(zhì)方法難以獲得的一些構(gòu)造信息。由于剪切帶內(nèi)應(yīng)變具有復(fù)雜性, 并且滲透大量流體, 導(dǎo)致AMS具有復(fù)雜性。因此對(duì)剪切帶開(kāi)展AMS研究工作, 在確定磁性礦物的基礎(chǔ)上, 識(shí)別AMS的形成階段以及多期次AMS的疊加就顯得十分關(guān)鍵。

致謝:由衷地感謝兩位匿名審稿人專業(yè)而又中肯的建議, 使作者受益良多！

陳柏林, 張招寵, 閆升好, 何立新, 周剛, 李麗, 蔣榮寶, 王祥, 張小林, 楊文平. 2007. 阿爾泰山南緣東段變形巖石磁組構(gòu)分析. 地學(xué)前緣, 14(3): 138–148.

陳應(yīng)濤, 張國(guó)偉, 魯如魁, 郭安林, 謝晉強(qiáng), 朱偉. 2019. 龍門山南段鹽井?五龍斷裂磁組構(gòu)特征及其對(duì)幾何學(xué)、運(yùn)動(dòng)學(xué)的制約. 大地構(gòu)造與成礦學(xué), 42(2): 199– 212.

段寶慶. 2015. 地震斷層帶流體作用的巖石物理和地球化學(xué)響應(yīng)——以龍門山斷裂花崗質(zhì)破裂帶為例. 北京: 中國(guó)地震局地質(zhì)研究所博士學(xué)位論文: 1–9.

何祥麗, 李海兵, 張蕾, 王煥, 葛成隆, 曹勇, 白明坤, 李成龍, 葉小舟, 韓帥. 2018. 龍門山灌縣?安縣斷裂帶斷層泥低磁化率的礦物、化學(xué)響應(yīng)和蠕滑作用環(huán)境. 地球物理學(xué)報(bào), 61(5): 1782–1796.

李陽(yáng), 梁文天, 靳春勝, 董云鵬, 袁洪林, 張國(guó)偉. 2017. 秦嶺沙溝街韌性剪切帶的巖石磁學(xué)、磁組構(gòu)和運(yùn)動(dòng)學(xué)渦度分析. 巖石學(xué)報(bào), 33(6): 1919–1933.

梁文天, 張國(guó)偉, 魯如魁, 裴先治, 袁四化, 姚安平. 2008. 西秦嶺北緣武山?鴛鴦鎮(zhèn)構(gòu)造帶磁組構(gòu)特征. 地學(xué)前緣, 15(4): 298–306.

林壽發(fā), 姜大志, Williams P F. 2007. 剪切帶運(yùn)動(dòng)學(xué): 重點(diǎn)評(píng)述三斜模式和區(qū)分韌性滑動(dòng)擦痕與拉伸線理的重要性. 地質(zhì)通報(bào), 26(9): 1139–1153.

劉貴. 2020. 韌性剪切帶內(nèi)得流體與巖石相互作用研究進(jìn)展. 地質(zhì)力學(xué)學(xué)報(bào), 26(2): 1–15.

劉江. 2019. 伸展褶劈理地質(zhì)現(xiàn)象、成因機(jī)制及其地質(zhì)意義. 地質(zhì)科技情報(bào), 38(2): 1–13.

潘永信, 朱日祥. 1998. 磁組構(gòu)研究現(xiàn)狀. 地球物理學(xué)進(jìn)展, 13(1): 52–56.

施建寧, 許同春, 董火根, 盧華復(fù). 1990. 浙閩碰撞造山帶中剪切帶的磁性組構(gòu)與碰撞動(dòng)力學(xué)的研究. 南京大學(xué)學(xué)報(bào), 26(1): 108–123.

孫靖鵬, 韓非, 鄧成龍, 潘永信. 2016. 山東膠萊盆地魯科一井上白堊統(tǒng)火山巖的巖石磁學(xué)和磁組構(gòu)研究. 地球物理學(xué)進(jìn)展, 31(6): 53–63.

孫曉明, 熊德信, 石貴勇, 王生偉, 翟偉. 2007. 云南哀牢山金礦帶大坪韌性剪切帶型金礦40Ar-39Ar定年. 地質(zhì)學(xué)報(bào), 81(1): 88–92.

王開(kāi), 賈東, 羅良, 董樹(shù)文. 2017. 磁組構(gòu)與構(gòu)造變形. 地球物理學(xué)報(bào), 60(3): 1007–1026.

吳漢寧. 1988. 巖石的磁性組構(gòu)及其在巖石變形分析中的應(yīng)用. 巖石學(xué)報(bào), 4(1): 96–100.

許順山, 陳柏林. 1998. 應(yīng)用巖石磁性組構(gòu)研究動(dòng)力變形作用. 地球?qū)W報(bào), 19(1): 19–24.

許志琴. 1989. 拉伸線理及其構(gòu)造意義. 四川地質(zhì)學(xué)報(bào), 9(2): 9–15.

楊朝斌, 朱大崗, 孟憲剛, 邵兆剛, 韓建恩, 余佳, 孟慶偉, 呂榮平. 2006. 西藏阿里雅魯藏布江縫合帶韌性剪切帶的磁組構(gòu)特征. 地學(xué)前緣, 13(4): 168–173.

袁學(xué)誠(chéng). 1991. 古地磁學(xué)原理及其應(yīng)用. 北京: 地質(zhì)出版社: 26–28.

確定指標(biāo)體系的常用方法包括層次分析法、專家咨詢法、主成分分析法、熵值法、非模糊數(shù)判定矩陣法、優(yōu)序圖法等[12]．選擇熵值法作為本文指標(biāo)體系權(quán)重的計(jì)算方法,其基本思路是通過(guò)計(jì)算指標(biāo)的信息熵,根據(jù)指標(biāo)的變化程度來(lái)決定指標(biāo)權(quán)重．信息量越小,不確定性就越大,熵也就越大;信息量越大,不確定性就越小,熵也就越小[13]．

曾佐勛, 樊光明, 王國(guó)燦, 李德威, 秦松賢, 張旺生, 索書田. 2008. 構(gòu)造地質(zhì)學(xué). 武漢: 中國(guó)地質(zhì)大學(xué)出版社: 210–225.

張蕾, 李海兵, 孫知明, 曹勇. 2019. 斷裂巖巖石磁學(xué)研究進(jìn)展. 地球?qū)W報(bào), 40(1): 157–172.

張蕾, 李海兵, 孫知明, 周佑民, 曹勇, 王煥, 葉小舟, 何祥麗. 2018. 龍門山斷裂帶大地震孕震環(huán)境的巖石磁學(xué)證據(jù). 地球物理學(xué)報(bào), 61(5): 1715–1727.

張蕾, 孫知明, 李海兵, 趙來(lái)時(shí), 曹勇, 葉小舟, 王雷振, 王煥, 何祥麗, 韓帥, 白明坤, 葛成隆, 趙越. 2017. 龍門山構(gòu)造帶WFSD-2鉆孔巖心磁化率特征及其對(duì)大地震活動(dòng)的響應(yīng). 地球物理學(xué)報(bào), 60(1): 225–239.

朱崗崑. 2005. 古地磁學(xué)——基礎(chǔ)、原理、方法、成果與應(yīng)用. 北京: 科學(xué)出版社: 1–9.

Abdeen M M, Greiling R O, Sadek M F and Hamad S S. 2014. Magnetic fabrics and Pan-African structural evolution in the Najd Fault corridor in the Eastern Desert of Egypt., 99(1): 93–108.

Anchuela ó P, Juan A P and Imaz A G. 2010. Tectonic imprint in magnetic fabrics in foreland basins: A case study from the Ebro Basin, N Spain., 492(1–4): 150–163.

Aranguren A, Cuevas J and Tubía J M. 1996. Composite magnetic fabrics from S-C mylonites., 18(7): 863–869.

Berthé D, Choukroune P and Jegouzo P. 1979. Orthogneiss, mylonite and non-coaxial deformation in granites: The example from South Armorican Shear Zone., 1(1): 31–42.

Bhathal R S. 1971. Magnetic anisotropy in rocks., 7(4): 227–253.

Biedermann A R. 2020. Current challenges and future development in magnetic fabric research., 795: 1–13.

Bikramaditya S R, Krishnakanta Singh A, Sen K and Sangode S J. 2017. Detection of a weak late-stage deformation event in granitic gneiss through anisotropy of magnetic susceptibility: Implications for tectonic evolution of the Bomdila Gneiss in the Arunachal Lesser Himalaya, Northeast India., 154(3): 476–490.

Billi A. 2005. Grain size distribution and thickness of breccia and gouge zones from thin (<1 m) strike-slip fault cores in limestone., 27(10): 1823–1837.

Biot A. 1965. Mechanics of Incremental Deformation. New York: John Wiley and Sons.

Blenkinsop T G and Treloar P J. 1995. Geometry, classificationand kinematics of S-C and S-C′ fabrics in the Mushandike area, Zimbabwe., 17(3): 397–408.

Borradaile G J. 1987. Anisotropy of magnetic-susceptibility- rock composition versus strain., 138: 327–329.

Borradaile G J. 1988. Magnetic susceptibility, petrofabrics and strain., 156(1): 1–20.

Borradaile G J. 1991. Correlation of strain with anisotropy of magnetic susceptibility (AMS)., 135(1): 15–29.

Borradaile G J and Alford C. 1987. Relationship between magnetic susceptibility and strain in laboratory experiments., 133: 121–135.

Borradaile G J and Alford C. 1988. Experimental shear zones and magnetic fabrics., 10(8): 895–904.

Borradaile G J and Henry B. 1997. Tectonic applications of magnetic susceptibility and its anisotropy., 42(1): 49–93.

Borradaile G J and Jackson M. 2004. Anisotropy of magnetic susceptibility (AMS): Magnetic petrofabrics of deformed rocks.,,, 238(1): 299–360.

Borradaile G J and Jackson M. 2010. Structural geology, petrofabrics and magnetic fabrics (AMS, AARM, AIRM)., 32(10): 1519–1551.

Borradaile G J and Tarling D H. 1981. The influence of deformation mechanisms on magnetic fabrics in weakly deformed rocks., 77(1): 151–168.

Brodsky E M, Kuo M F, Mori J and Saffer D M. 2009. Rapid response fault drilling past, present, and future., 8(8): 66–74.

Casas-Sainz A M, Gil-Imaz A, Simón J L, Izquierdo-Llavall E, Aldega L, Román-Berdiel T, Osácar M C, Pueyo- Anchuela ó, Ansón M, García-Lasanta C, Corrado S, Invernizzi C and Caricchi C. 2018. Strain indicators and magnetic fabric in intraplate fault zones: Case study of Daroca thrust, Iberian Chain, Spain., 730(4): 29–47.

Casas-Sainz A M, Román-Berdiel T, Oliva-Urcia B, García- Lasanta C, Villalaín J J, Aldega L, Corrado S, Caricchi C, Invernizzi C and Osácar M C. 2017. Multidisciplinary approach to constrain kinematics of fault zones at shallow depths: A case study from the Cameros-Demanda thrust (North Spain)., 106(3): 1023–1055.

Chen X Y, Liu J L, Weng S T, Kong Y L, Wu W B, Zhang L S and Li H Y. 2016. Structural geometry and kinematics of the Ailao Shan shear zone: Insights from integrated structural, microstructural, and fabric studies of the Yao Shan complex, Yunnan, Southwest China., 58(7): 849–873.

Chou Y M, Song S R, Aubourg C, Song Y F, Boullier A M, Lee T Q, Evans M, Yeh E C and Chen Y M. 2013. Pyrite alteration and neoformed magnetic minerals in the fault zone of the Chi-Chi earthquake (Mw7.6, 1999): Evidence for frictional heating and co-seismic fluids.,,, 13(8): 1–17.

Chou Y M, Song S R, Tsao T M, Lin C S, Wang M K, Lee J J and Chen F J. 2014. Identification and tectonic implications of nano-particle quartz (~50 nm) by synchrotron X-ray diffraction in the Chelungpu fault gouge Taiwan., 619–620: 36–43.

Cifelli F, Mattei M, Chadima M, Hirt A M and Hansen A. 2005. The origin of tectonic ineation in extensional basins: Combined neutron texture and magnetic analyses on “undeformed” clays., 235: 62–78.

Dell’Angelo L N and Olgaard D L. 1989. Fabric development in experimentally sheared quartzites., 169: 1–21.

Deng J, Yang L, Gao B F, Sun Z S, Guo C Y, Wang Q F and Wang J P. 2009. Fluid evolution and metallogenic dynamics during tectonic regime transition: Example from the Jiapigou gold belt in Northeast China., 59(2): 140–152.

Dimanov A, Dresen G and Wirth R. 1998. High-temperature creep of partially molten plagioclase aggregates.:, 103(B5): 9651– 9664.

Dudzisz K, Szaniawski R, Michalski K and Chadima M. 2018. Rock magnetism and magnetic fabric of the Triassic rocks from the West Spitsbergen Fold-and- Thrust Belt and its foreland., 728(20): 104–118.

Enomoto Y, Akai M, Hashimoto H, Mori S and Asabe Y. 1993. Exoelectron emission: Possible relation to seismic geo-electromagnetic activities as a microscopic aspect in geotribology., 168(1–2): 135–142.

Faulkner D R, Lewis A C and Rutter E. 2003. On the internal structure and mechanics of large strike-slip fault zones: Field observations of the Carboneras fault in southeastern Spain., 367(3): 235–251.

Ferré E C and Améglio L. 2000. Preserved magnetic fabrics vs. annealed microstructures in the syntectonic recrystallised George granite, South Africa., 22: 1199–1219.

Ferré E C, Gébelin A, Till J L, Sassier C and Burmeister K C. 2014. Deformation and magnetic fabrics in ductile shear zones: A review., 629: 179–188.

Flinn D. 1962. On folding during three-dimensional progressivedeformation., 118: 385–433.

Flinn D. 1965. On the symmetry principle and the deformation ellipsoid., 102(1): 36–45.

Fossen H, Carolona G and Cavalcante G. 2017. Shear zones —A review., 171: 434–455.

Fukuchi T, Mizoguchi K and Shimamoto T. 2005. Ferrimagnetic resonance signal produced by frictional heating: A new indicator of paleoseismicity., 110, B12404.

Fuller M. 1961. Magnetic Anisotropy of Rocks. UK: Cambridge University: 1–20.

Fuller M. 1963. Magnetic anisotropy and paleomagnetism., 68: 293–309.

Ge J Y, Guo Z T, Zhao D A, Zhang Y, Wang T, Yi L and Deng C L. 2014. Spatial variations in paleowind directionduring the last glacial period in north China reconstructed from variations in the anisotropy of magnetic suscepti-bility of loess deposits., 629(26): 353–361.

Gehring A U and Hofmeister A M. 1994. The transformation of lepidocrocite during heating: A magnetic and spec-troscopic study., 42: 409–415.

Goldstein A G and Brown L L. 1988. Magnetic susceptibility anisotropy of mylonites from the Brevard Zone, North Carolina, USA., 51: 290–300.

Gordon R G. 1995. Plate motion, crustal and lithospheric mobility, and paleomagnetism: Prospective viewpoint., 100: 24367–24392.

Graham W J. 1954. Magnetic susceptibility anisotropy, an unexploited petrofabric element., 65: 1257–1258.

Hailwood E A, Maddock R H, Fung T and Rutter E H. 1992. Paleomagnetic analysis of fault gouge and dating fault movement, Anglesey, North Wales., 149(2): 273–284.

Han R, Shimamoto T, Ando J I and Ree J H. 2007. Seismic slip record in carbonate-bearing fault zones: An insight from high-velocity friction experiments on siderite gouge., 35(12): 1131–1134.

Henry B. 1983. Interprétation quantitative de l’anisotropie de susceptibilité magnétique., 91(1): 165–177.

Hirono T, Lin W, Yeh E C, Soh W, Hashimoto Y, Sone H, Matsubayshi O, Aoike K, Ito H, Kinoshita M, Masafumi M, Song S R, Ma K F, Hung J H, Wang C Y and Tsai Y B. 2006. High magnetic susceptibility of fault gouge within Taiwan Chelungpu fault: Nondestructive continuous measurements of physical and chemical properties in fault rocks recovered from Hole B, TCDP., 33(15): L15303.

Hirt A M and Gehring A U. 1991. Thermal alteration of the magnetic minerality in ferruginous rocks., 96(B6): 9947–9953.

Hrouda F. 1982. Magnetic anisotropy of rocks and its application in geology and geophysics., 5(1): 37–82.

Hrouda F and Faryad S W. 2017. Magnetic fabric overprints in multi-deformed polymetamorphic rocks of the GemericUnit (Western Carpathians) and its tectonic implications., 717(16): 83–89.

Hrouda F and Janák F. 1976. The changes in shape of the magnetic susceptibility ellipsoid during progressive metorphism and deformation., 34(1–2): 135–148.

Hrouda F, Krej?íc O, Potfajd M and Stráník Z. 2009. Magnetic fabric and weak deformation in sandstones of accretionary prisms of the Flysch and Klippen Belts of the Western Carpathians: Mostly off scraping indicated., 479: 254–270.

Humbert F, Robion P, Louis L, Bartier D, Ledésert B and Song S R. 2012. Magnetic inference ofopen microcracks in sandstone samples from the Taiwan Chelungpu Fault Drilling Project (TCDP)., 45: 179–189.

Hunt C P, Moskowitz B M and Banerjee S. 1995. Magnetic Properties of Rocks and Minerals. Rock Physics and Phase Relations: A Handbook of Physical Constants, 3: 189–204.

Ising G. 1942. On the magnetic properties of varved clay.,, 29A: 1–37.

Jackson M. 1991. Anisotropy of magnetic remanence: A brief review of mineralogical sources, physical origins, and geological applications, and comparison with susceptibility anisotropy., 136(1): 1–28.

Jackson M, Borradaile G, Hudleston P and Banerjee S. 1993. Experimental deformation of synthetic magnetite- bearing calcite sandstones: Effects on remanence, bulk magnetic properties, and magnetic anisotropy., 98(B1): 383–401.

Jelínek V. 1978. Statistical processing of anisotropy of magnetic susceptibility measures on groups of specimens., 22: 50–62.

Jiang D Z and Williams P F. 1998. High-strain zones: A unified model., 20(8): 1105–1120.

Johns M and Jackson M. 1991. Compositional control of anisotropy of remanent and induced magnetization in synthetic samples., 18(7): 1293–1296.

Just J, Kontny A, Wall D H, Hirt A M and Martín F. 2004. Development of magnetic fabrics during hydrothermal alteration in the Soultz-sous-Forets granite from the EPS1 borehole, Upper Rhine Graben.,,, 238: 509–526.

Kanamatsu T, Parés J M and Kitamura Y. 2012. Pliocene shortening direction in Nankai Trough off Kumano, southwest Japan, Sites IODP C0001 and C0002, Expedition 315: Anisotropy of magnetic susceptibility analysis for paleostress.,,, 13(1): 1–13.

Kankeu B, Greiling R and Nzenti J P. 2009. Pan-African strike-slip tectonics in eastern Cameroon-Magnetic fabrics (AMS) and structure in the Lom basin and its gneissic basement., 174: 258–272.

Kley J and Voigt T. 2008. Late Cretaceous intraplate thrusting in central Europe: Effect of Africa-Iberia Europe convergence, Not Alpine collision., 36(11): 839–842.

Kligfield R, Lowrie W and Priffner O A. 1982. Magnetic properties of deformed oolitic limestones from the Swiss Alps: The correlation of magnetic anisotropy and strain., 75: 127–157.

Koziol A M. 2004. Experimental determination of siderite stability and application to Martian Meteorite ALH84001., 89(2–3): 294–300.

Kuo L W, Song S R, Yeh E C, Chen H F and Si J L. 2012. Clay mineralogy and geochemistry investigations in the host rocks of the Chelungpu fault, Taiwan: Implication for faulting mechanism., 59: 208–218.

Law R D, Knipe R J and Dayan H. 1984. Strain path partitioning within thrust sheets: Microstructural and petrofabric evidence from the Moine Thrust zone at Loch Eriboll, northwest Scotland., 6(5): 477–497.

Levi T and Weinberger R. 2011. Magnetic fabrics of diamagnetic rocks and the strain field associated with the Dead Sea Fault, northern Israel., 33(4): 566–578.

Lin S F, Jiang D Z and Williams P F. 1998. Transpression (or transtension) zones of triclinic symmetry: Natural example and theoretical modelling.,,, 135: 41–57.

Lin S F, Jiang D Z and Williams P F. 2007. Importance of differentiating ductile slickenside striations from stretching lineations and variation of shear direction across a high-strain zone., 29: 850–862.

Lin S F and Williams P F. 1992a. The origin of ridge-in- groove slickenside striae and associated steps in an S-C mylonite., 14(3): 315–321.

Lin S F and Williams P F. 1992b. The geometrical relationship between the stretching lineation and the movement direction of shear zones., 14: 491–497.

Lin W, Doan M L, Moore C, McNeill L, Byrne T B, Ito T, Saffer D, Conin M, Kinoshita M, Sanada Y, Moe K T, Araki E, Tobin H, Boutt D, Kano Y, Buret C, Schleicher A M, Efimenko N, Kawabata K, Buchs D M, Jiang S, Kaneo K, Horiguchi K, Wiersberg T, Kopf A, Kitada K, Eguchi N, Toczko S, Takahashi K and Kido Y. 2010. Present-day principal horizontal stress orientations in the Kumano forearc basin of the southwest Japan subduction zone determined from IODP NanTroSEIZE drilling Site C0009., 37(L13303): 1–6.

Lister G S and Snoke A W. 1984. S-C mylonites., 6: 617–638.

Liu D, Li H, Lee T Q, Chou Y M, Song S R, Sun Z M, Chevalier M L and Si J L. 2014. Primary rock magnetism for the Wenchuan earthquake fault zone at Jiulong outcrop, Sichuan Province, China., 619–620: 58–69.

Liu W M and Sun J M. 2012. High-resolution anisotropy of magnetic susceptibility record in the central Chinese Loess Plateau and its paleoenvironment implications.:, 55(3): 488–494.

Mamtani M A and Sengupta P. 2010. Significance of AMS analysis in evaluating superposed folds in quartzites., 147(6): 910–918.

Marcén M, Casas-Sainz A M, Román-Berdiel T, Oliva-Urcia, Soto R and Aldega. 2018. Kinematics and strain distribution in an orogeny-scale shear zone: Insights from structural analyses and magnetic fabrics in the Gavarnie thrust, Pyrenees., 117: 105–123.

Marcén M, Casas-Sainz A M, Román-Berdiel T, Oliva-Urcia B, Soto R, García-Lasanta C, Calvin P, Gil-Imaz A and Aldega L. 2020. Magnetic fabric in brittle faults and ductile shear-zones: Examples from cataclasites from the Iberian Peninsula. EGU General Assembly: 1–2.

Mean W D. 1987. A newly recognized type of slickenside striation., 9: 585–590.

Medina-Cascales I, Koch L, Cardozo N, Martin-Rojas I, Alfaro P and García-Tortosa F J. 2019. 3D geometry and architecture of a normal fault zone in poorly lithified sediments: A trench study on a strand of the Baza Fault, central Betic Cordillera, South Spain., 121: 25–45.

Mims C V H, Powell C A and Ellwood B. 1990. Magnetic susceptibility of rocks in the Nutbush Creek ductile shear zone, North Carolina., 178: 207–223.

Mishima T, Hirono T, Nakamura N, Tanikawa W, Soh W and Song S S. 2009. Changes to magnetic minerals caused by frictional heating during the 1999 Taiwan Chi-Chi earthquake., 61: 797–801.

Mishima T, Hirono T, Soh W and Song S R. 2006. Thermal history estimation of the Taiwan Chelungpu fault using rock-magnetic methods., 33, L23311.

Mondal T K. 2018. Evolution of fabric in Chitradurga granite (south India) — A study based on microstructure, anisotropy of magnetic susceptibility (AMS) and vorticity analysis., 723(16): 149–161.

Mondal T K and Mamtani M A. 2013. 3D Mohr circle construction using vein orientation data from Gadag (southern India)-Implications to recognize fluid pressure fluctuation., 56: 45–56.

Moore G F. 1989. Tectonics and hydrogeology of accretionary prisms: Role of the décollement zone., 11(1-2): 95–106.

Nagaraju E and Parashuramulu V. 2019. AMS studies on a 450 km long 2216 Ma dyke from Dharwar craton, India: Implications to magma flow., 10: 1931–1939.

Nagata T. 1961. Rock Magnetism. Tokyo: Maruzen: 1–350.

Nakamura N and Nagahama H. 2001. Changes in magnetic and fractal properties of fractured granites near the Nojima fault, Japan., 10(3-4): 486–494.

Novak B, Housen B, Kitamura Y, Kanamatsu T and Kawamura K. 2014. Magnetic fabric Analyses as a method for determining sediment transport and deposition in deep sea sediments., 356(6): 19–30.

Nye J F. 1957. Physical Properties of Crystals. London: Oxford University: 1–60.

Ono T, Housomi Y, Arai H and Takagi H. 2010. Comparison of petrofabrics with composite magnetic fabrics of S-C mylonite in paramagnetic granite., 32: 2–14.

Owens W H. 1974. Mathematical model studies on factors affecting the magnetic anisotropy of deformed rocks., 24: 115–131.

Owens W H. 1993. Magnetic fabric studies of samples from hole 808C, Nankai Trough.,, 131: 301–310.

Parés J M. 2015. Sixty years of anisotropy of magnetic susceptibility in deformed sedimentary rocks., 3(4): 1–13.

Parés J M and van der Pluijm B A. 2002. Evaluating magnetic lineations (AMS) in deformed rocks., 350: 283–298.

Parés J M and van der Pluijm B A. 2004. Correlating magnetic fabrics with finite train: Comparing results from mudrocks in the Variscan and Appalachian Orogens., 2: 213–220.

Parés J M, van der Pluijm B A and Turell J D. 1999. Evolution of magnetic fabrics during incipient deformationof mudrocks (Pyrenees, northern Spain)., 307: 1–14.

Pechersky D M and Genshaft Y S. 2001. Petromagnetism of the continental lithosphere and the origin of regional magnetic anomalies: A review., 3(2): 97–124.

Pei J, Li H B, Wang H, Si J L, Sun Z M and Zhou Z Z. 2014. Magnetic properties of the Wenchuan Earthquake Fault Scientific Drilling Project Hole-1(WFSD-1), Sichuan province, China., 66(1): 23.

Platt J P and Vissers R L M. 1980. Extensional structures in anisotropic rocks., 2(4): 397–410.

Raposo M I B and Berquo T S. 2008. Tectonic fabric revealed by AARM of the proterozoic mafic dike swarm in the Salvador city (Bahia State): S?o Francisco Craton, NE Brazil., 167(3–4): 179–194.

Raposo M I B, Drukas C O and Basei M A S. 2014. Deformation in rocks from Itajaí basin, Southern Brazil, revealed by magnetic fabrics., 629(26): 290–302.

Rasmay J G. 1980. Shear zone geometry: A review., 2: 83–99.

Rathore J S. 1980. The magnetic anisotropy of same slates from the Borrow dale volcanic group in the English Lake district and their correlation with strain., 67: 207–220.

Rathore J S. 1981. The magnetic fabric of some slates from the Borrow dale volcanic group in the English Lake rocks., 77: 151–168.

Rathore J S and Becke M. 1980. Magnetic fabric analyses in the Gail Galley (Carinthia, Austria) for the determination of the sense of movements along this region of the Periadriatic Line., 69: 349–368.

Robl J, Fritz H, Stüwe K and Bernhard F. 2004. Cyclic fluid infiltration in structurally controlled Ag-Pb-Cu occurrences (Schladming, Eastern Alps)., 205(1–2): 17–36.

Román-Berdiel T, Casas-Sainz A M, Oliva-Urcia B, Calvín P and Villalaín J J. 2019. On the influence of magnetic mineralogy in the tectonic interpretation of anisotropy of magnetic susceptibility in cataclastic fault zones., 216(2): 1043–1061.

Saint-Bezar B, Hebert R L, Aubourg C, Robion P, Swennen R and de Lamotte D F. 2002. Magnetic fabric and petrographic investigation of hematite-bearing sandstones within ramp-related folds: Examples from the South Atlas Front (Morocco)., 24: 1507–1520.

Sibson R H. 1977. Fault rocks and fault mechanisms., 133(3): 191–213.

Sibsona R H and Scott J. 1988. Stress/fault controls on the containment and release of overpressured fluids: Examplesfrom gold-quartz vein systems in Juneau, Alaska; Victoria, Australia and Otago, New Zealand., 13(1–5): 293–306.

Simpson C and Schmid S M. 1984. An evaluation of criteria to deduce the sense of movement in sheared rocks., 94: 1281–1288.

Solum J G and van der Pluijm B. 2009. Quantification of fabrics in clay gouge from the Carboneras fault, Spain and implications for fault behavior., 475(3): 554–562.

Soto R, Larrasoa?a J C, Arlegui L E, Beamud E, Oliva-Urcia B and Simón J L. 2009. Reliability of magnetic fabric of weakly deformed mudrocks as a palaeostress indicator in compressive settings., 31(5): 512–522.

Stacey F D, Joplin G and Lindsay J. 1960. Magnetic anisotropy and fabric of some foliated rocks from S.E. Australia., 47(1): 30–40.

Stephenson A, Sadikun S and Potter D K. 1986. A theoretical and experimental comparison of the anisotropies of magnetic susceptibility and remanence in rocks and minerals., 84(1): 185–200.

Stern R J. 2005. TECTONICS丨Ocean Trenches. Encyclopedia of Geology: 428–437. doi.org/ 10.1016/B0-12-369396-9/00141-6

Tanikawa W, Mishima T, Hirono T, Lin W, Shimamoto T, Soh W and Song S R. 2007. High magnetic susceptibility produced in high-velocity frictional tests on core samples from the Chelungpu fault in Taiwan., 34: L15304.

Tarling D H and Hrouda F. 1993. The Magnetic Anisotropy of Rocks. London: Chapman and Hall: 1–217.

Thompson R and Oldfield F. 1986. Environmental magnetism. London: Allen and Unwin: 1956: 1–227.

Till J L and Moskowitz B M. 2014. Deformation microstructures and magnetite texture development in synthetic shear zones., 629: 211–223.

Tomezzoli R N, MacDonald W D and Tickyj H. 2003. Composite magnetic fabrics and S-C structure in granitic gneiss of Cerro de los Viejos, La Pampa province, Argentina., 25: 159–169.

Ujiie K, Hisamitsu T and Soh W. 2000. Magnetic and structural fabrics of the melange in the Shimanto accretionary complex, Okinawa Island: Implication for strain history during decollement-related deformation., 105(B11): 25729– 25741.

Ujiie K, Hisamitsu T and Taira A. 2003. Deformation and fluid pressure variation during initiation and evolution of the plate boundary decollement zone in the Nankai accretionary prism.:, 108: 1–8.

Uyeda S, Fuller M D, Belshé J C and Girdler R W. 1963. Anisotropy of magnetic susceptibility of rocks and minerals., 68(1): 279–291.

Vikas C, Prasannakumar V and Pratheesh P. 2016. Role of microfabrics and magnetic fabrics in the tectonic evolution of the Achankovil shear-zone, South India., 131: 95–108.

Voight W and Kinoshita S. 1907. Bestimmung absoluter Werte von Magnetiserungszahlen, inbesondere für Kristalle., 24: 492–514.

White S H, Burrows S E, Carreras J, Shaw N D and Humphreys F J. 1980. On mylonites in ductile shear zones., 2(1–2): 175–187.

Wiegand M, Trumbull R B, Kontny A and Greiling R O. 2017. An AMS study of magma transport and emplacementmechanisms in mafic dykes from the Etendeka Province, Namibia., 716: 149–167.

Wise D U, Dunn D E, Engelder J T, Geiser P A, Hatcher R D, Kish S A, Odom A L and Schamel S. 1984. Fault-related rocks: Suggestions for terminology., 12(7): 391–394.

Yang T, Chen J Y, Wang H Q and Jin H Q. 2012a. Rock magnetic properties of fault rocks from the rupture of the 2008 Wenchuan Earthquake, China and their implications: Preliminary results from the Zhaojiagou outcrop, Beichuan County (Sichuan)., 530–531: 331–341.

Yang T, Chen J Y, Wang H Q and Jin H Q. 2012b. Magnetic properties of fault rocks from the Yingxiu-Beichuan fault: Constraints on temperature rise within the shallow slip zone during the 2008 Wenchuan Earthquake and their implications., 50: 52–60.

Yang T, Chen J Y, Xu H R and Dekkers M J. 2019. High-velocity friction experiments indicate magnetic enhancement and softening of fault gouges during seismic slip.:, 124: 26–43.

Yang T, Chou Y M, Ferré E C, Dekkers M J, Chen J, Yeh E C and Tanikawa W. 2020. Faulting processes unveiled by magnetic properties of fault rocks., 58: 1–60.

Yang T, Dekkers M J and Zhang B. 2016. Seismic heating signatures in the Japan Trench subduction plate-boundary fault zone: Evidence from a preliminary rock magnetic ‘geothermometer’., 205(1): 319–331.

Yang T, Mishima T, Ujiie K, Chester F M, Mori J, Eguchi N, Toczko S and Expedition 343 Scientists. 2013. Strain decoupling across the décollement in the region of large slip during the 2011 Tohoku-Oki earthquake from anisotropy of magnetic susceptibility., 381: 31–38.

Yeh E, Lee T, Lin Y, Chou Y and Lu C. 2007. Analysis of magnetic and grain fabrics across fault gouge in the Chelungpu Fault of Taiwan (Abstract T43B-1331). Paper presented at American Geophysical Union Fall Meeting 2007, San Francisco, USA.

Zhang L, Li H B, Sun Z M, Chou Y M, Cao Y and Wang H. 2018. Metallic iron formed by melting: A new mechanism for magnetic highs in pseudotachylyte., 46(9): 779–782.

Zhou Y, Zhou P, Wu S M, Shi X B and Zhang J J. 2020. Magnetic fabric study across the Ailao Shan-Red River shear zone., 346: 137–150.

Ziegler P A. 1989. Geodynamic model for Alpine intraplate compressional deformation in Western and Central Europe.,,, 44(1): 63–85.

Anisotropy of Magnetic Susceptibility and Shear Zone

HUA Tian1, LI Jinxi2*, LI Zhiwu1, RAN Bo1, TONG Kui1, WANG Zijian1, YUAN Mengyu1, CAI Hongyan1, CHEN Tao1, LI Ke3and LIU Shengwu1

(1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, Sichuan, China; 2. MOEKey Laboratory of Earth Exploration and Information Technology, College of Geophysics, Chengdu University of Technology, Chengdu 610059, Sichuan, China;3. Sichaun Institude of Coal Field Geological Engineering Explortation and Designing, Chengdu 610072, Sichuan, China)

Rock records and preserves critical information about the transformation and evolution of the crust. Extracting such information is of great significance for analyzing and restoring geodynamic processes. Anisotropy of magnetic susceptibility (AMS) is an important rock fabric, which effectively records the rock strain characteristics. It can be used to analyze the geodynamic process and is an effective method to study structural deformation and stress effects. In this paper, the basic principle of AMS and its application in shear zone are systematically described on the basis of the research history, main achievements and the latest progress of AMS. We can come to conclusions as below: (1) The rock fabric is complex, and the magnetic fabric, as an indirect means of fabric, is controlled by the physical properties of minerals, the types and contents of magnetic minerals, deformation and metamorphism. (2) The determination of magnetic minerals is the key to the study of magnetic fabric. (3) In most cases, there is a coaxial relationship between the principal axis of the magnetic ellipsoid and the strain ellipsoid, thus the magnetic ellipsoid can be used as “display” of rock deformation. (4)In the shear zone, AMS can obtain some structural information which is difficult to obtain by conventional geological methods. However, due to the complexity of shear zone and magnetic fabric, this method should be used with caution. It is necessary to make a reasonable explanation for its origin using geologic evidence from different aspects. (5) Strain across shear zone is typically heterogeneous, which leads to the different orientation of the magnetic fabric. Moreover, deformation is commonly accompanied by fluid-rock interaction or mineral segregation. The interaction between fluid and rock induces changes in magnetic mineralogy. (6) In shear zone, the relationship betweenjand strain depends strongly on the deformation mechanisms and the mineral carriers of AMS as well.

anisotropy of magnetic susceptibility; AMS; shear zone; rock fabric

2019-08-05;

2020-06-01

國(guó)家自然科學(xué)基金項(xiàng)目(41602153、41472107、41230313)資助。

華天(1995–), 男, 碩士研究生, 構(gòu)造地質(zhì)學(xué)專業(yè)。Email: tianhuamag@163.com

李金璽(1981–), 男, 副教授, 從事構(gòu)造地質(zhì)學(xué)及地球物理研究與教學(xué)工作。Email: lijinxi23@qq.com

P545

A

1001-1552(2021)02-0280-016

10.16539/j.ddgzyckx.2021.02.002