秦岭柞水岩体锆石U-Pb年龄及其地质意义

柞水岩体侵位于秦岭造山带商丹缝合带附近,具有比较典型的环斑花岗结构,本文获得了213.6±1.8 Ma的单颗粒锆石 U-Pb 年龄,MSWD 为 1.5,这个年龄与前人在东秦岭沙河湾环斑花岗岩测定的锆石 U-Pb年龄非常一致。研究表明,柞水岩体的主元素、微量元素及稀土元素地球化学、Sr 同位素初始值 I_(Sr)等清楚的显示具有I-型和A-型花岗岩特征,大地构造环境判别属碰撞后隆升阶段或造山后花岗岩。这些特征也与秦岭沙河湾环斑花岗岩及西秦岭环斑花岗岩非常相似。因此,柞水岩体锆石 U-Pb 年龄的获得,使得秦岭造山带环斑花岗岩很可能从东向西断续呈带状展布,贯通东西秦岭。由此可以确认,在秦岭造山带主造山期晚期或主造山期后曾经存在过一次短暂的垂直于造山带的拉伸或松弛坍塌构造阶段,这对研究整个秦岭造山带的演化无疑具有重要意义。     

北秦岭老君山环斑花岗岩的成因及大地构造意义

老君山环斑花岗岩分布于北秦岭造山带中，是沙河湾、朱厂沟脑、秦岭梁北秦岭环斑花岗岩带的一部分，以特殊的环斑结构，富含基性暗色微粒包体为特征，通过对其地质、岩石、地化资料研究，结合区域大地构造环境，认为老君山环斑花岗岩，具有岩浆混合成因类型，为造山后伸展环境的产物，标志着印支期末秦岭地区俯冲碰撞的板块构造体制已经结束，转入板内构造演化阶段。     

答“对秦岭奥长环斑花岗岩质疑”

环斑花岗岩是一种特殊结构的花岗岩类，并且多数产在元古宙克拉通中。笔者曾报道了在秦岭造山带中发育有印支期具有环斑结构的花岗质岩石。“对秦岭奥长环斑花岗岩质疑”一文认为它们不是环斑花岗岩，并引用Ramo的图表来说明自己的观点。本文将从以下几方面进行讨论：秦岭环斑花岗岩的研究历史；环斑花岗岩的定义；世界上环斑花岗岩的成因类型；秦岭环斑花岗岩的副矿物及铁镁含量和环斑钾长石特征；秦岭环斑花岗岩与基性岩共存等。本文还论证了秦岭环斑花岗岩不同于元古宙非造山环斑花岗岩，而是一种造山型的环斑花岗岩，其形成于后造山环境，是挤压（造山）向拉张（稳定）转折时期的产物。最后对研究秦岭环斑花岗岩的几个理论问题进行了探讨。     

新疆和硕东泉戈壁环斑花岗岩的成因及地质意义

通过1∶5万马兰幅区域地质调查,首次在东泉戈壁地区发现了环斑花岗岩。东泉戈壁环斑花岗岩分布于南天山碰撞带中部,岩体以富含暗色细粒闪长质包体和具有特殊的环斑结构为特征。该花岗岩呈岩株状产出,岩石化学以较高的Al2O3(14.47%～15.44%)、K2O(3.93%～4.7%)和Na2O(3.4%～3.7%),富集轻稀土和大离子亲石元素,具有弱的δEu(平均为0.79)负异常等为特征,表现出与典型的板内奥长环斑花岗岩明显不同的地球化学特征。其形成时代为晚石炭世(305±1Ma),恰好是南天山洋盆向北俯冲碰撞造山末期阶段,据此认为东泉戈壁环斑花岗岩可能是一种造山带型环斑花岗岩,形成于板块碰撞后的抬升环境下的I型花岗岩。     

秦岭环斑花岗岩的年代学研究及其意义

本文对秦岭环斑花岗岩带进行了系统的测年工作,通过对实测Ｕ－Ｐｂ,Ｒｂ－Ｓｒ,＾４０Ａｒ／＾３９Ａｒ年龄测定结果研究,认为２１０－２１７Ｍａ是秦岭造山带主造山阶段结束的时间,为秦岭主造山期结束提供了确切的语气具有重要的科学意义。     

都庞岭岩体环斑花岗岩的特征

都庞岭复式岩体内包括有志留纪、晚三叠世、中侏罗世等三个时代花岗岩。通过岩石学研究发现晚三叠世三个单元的花岗岩均具斜长环斑结构，为黑云母奥长环斑花岗岩。环斑花岗岩酸碱性程度高，富钾及稀土元素，铕亏损明显，富铷贫锶，似钾质花岗岩；Nd，Sr，Pb等同位素具低级上地壳物质特征，εNd(t)值—8．2，t2DM值1660Ma，可能为中元古代沉积物及其内所夹火山物质熔融物；多数特征介于复式岩体内的志留纪花岗岩和中侏罗世花岗岩之间，但最富钾，明显不同于秦岭地区沙河湾环斑花岗岩体，部分特征相似或比较近似于华北地台沙厂环斑花岗岩和芬兰Ahvenisto地块黑云母环斑花岗岩。     

北秦岭老君山和秦岭梁环斑结构花岗岩及构造环境——一种可能的造山带型环斑花岗岩

老君山和秦岭梁岩体产于秦岭造山带商丹缝合带北侧,其岩石普遍发育环斑结构,表现为碱性长石巨晶多为卵球状,有些发育斜长石外壳,有些不发育。这不同于一般花岗岩局部出现的具斜长石外壳自形碱性长石巨晶结构。在地球化学上,该岩石显示I—A型花岗岩过渡特点。区域背景、构造被动定位特点和地球化学综合分析表明,它们可能定位于后碰撞或后造山环境。这些特征与典型的元古代克拉通非造山环境中的环斑花岗岩既有相似之处,也有一定差异,而与巴西造山带中环斑花岗岩较为相似。本文认为,它们不是一般的斑状花岗岩,而是最近注意研究的环斑结构花岗岩,有可能是一种造山带型环斑花岗岩,即产于造山带中的非典型环斑花岗岩。     

对秦岭奥长环斑花岗岩的质疑

本文介绍了环斑结构的含义及奥长环斑花岗岩的地质与地球化学特征。在此基础上对所谓的秦岭奥长环斑花岗岩带提出质疑，并提出秦岭中的一些花岗岩虽然具有环斑结构，但不是奥长环斑花岗岩。     

柴达木盆地北缘塔塔楞环斑花岗岩的岩相学和地球化学特征

塔塔楞环斑花岗岩是柴迭木盆地北缘一个古生代复式岩体.该环斑花岗岩的主量元素具有富SiO2、K2O和FeO*.高K2O/Na2O和FeO*/MgO的特点,其平均值分别为72.86%、5.17%和3.35%,2.22和10.73;∑REE在279.1×10-6～300.3×10-6之间.(La/Lu)N为11.32～13.14,δEu在0.28～0.38之间;Ba、Kb、Pb、Th等元素的含量高.而Sr、Cr、Ni、V等元素的含量低.与经典环斑花岗岩相比,二者在岩相学上相同,在地球化学土也有相似之处,即该岩体也表现为高钾、富铁、富LREE和Eu亏损的特征,但部分微量元素与典型环斑花岗岩有一定差异.岩体的形成时代和区域构造背景的综合分析显示,该岩体可能是早古生代后碰撞或后造山伸展构造环境下的产物.     

秦岭-昆仑造山型环斑花岗岩与世界典型环斑花岗岩的对比

通过秦岭-昆仑造山带中的环斑花岗岩同世界元古宙环斑花岗岩的岩石学、岩相学、岩石地球化学和构造环境等方面的对比研究发现,二者具有相同或一致的特征:具环斑结构,属准铝、高钾、富碱岩浆,具双峰式岩浆组合,形成于后碰撞环境,但其地球化学的某些指标、岩浆形成时代和出露的大地构造位置等有一定差异.世界元古宙环斑花岗岩的岩石化学及暗色矿物明显富铁,w(FeT)/w(FeT Mg)较高,多数在0.9以上,岩石成因类型多数是A型花岗岩,产在稳定地台区的边缘,而昆仑地区多数环斑花岗岩的w(FeT)/w(FeT MgO)＞0.8,亦较富Fe,且多数是A型花岗岩;秦岭地区的岩体铁指数相对较低,只有0.62,岩石成因类型的地球化学判据既有A型也有Ⅰ型花岗岩特征.秦岭-昆仑造山带中环斑花岗岩的显著特征是都产在造山带中,与板块缝合带关系密切,时代从元古宙到古生代直到中生代都有发现,具多旋回性.它们出现在每一个大的造山旋回晚期,即向另一个构造旋回的转折期,这在世界造山带中是十分罕见的,反映出世界上造山带与稳定区元古宙和显生宙的地幔与地壳状态是不一样的,有着不同的构造演化历史和动力学过程,表明秦岭-昆仑地区的环斑花岗岩是一种有别于元古宙稳定区的造山型环斑花岗岩.     

西秦岭造山带泥盆纪沉积地质学和动力沉积学研究:古地理、地层层序及构造演化

晚加里东到早海西期，西秦岭北带存在一较大规模的造山带，泥盆纪的古地形呈北高南低的特征。持续的海侵由南向北侵进、中泥盆世由于北秦岭造山带的向南仰冲，形成同造山的前陆拗陷盆地。南秦岭裂陷槽是早古生代小洋盆的残余海槽。西秦岭造山带泥盆纪的地层层序分为海平面变化控制型层序（ＳＣ型）、基底构造控制型层序（ＴＣ型）和复合型层序（ＳＴＣ型）三种类型。ＳＣ型层序发育于中秦岭微板块的小型克拉通盆地，ＴＣ型层序发育于同造山盆地和相邻的前隆（反弹）带，ＳＴＣ型层序是造山作用和造山过程的沉积响应。秦岭造山带加里东－早海西期碰撞－造山作用过程较为复杂，北秦岭造山带是由秦岭微板块与华北板块斜向和不规则边缘碰撞形成的，是一个发育不成熟和不均一的造山带，碰撞和造山由西向东，造山作用在西秦岭表现显著；南秦岭洋盆的闭合是秦岭微板块和扬子板块的斜向碰撞形成的，具闭合不碰撞和碰撞不造山的特征，闭合和碰撞由东向西。晚海西－印支期，秦岭进入再生盆地发育阶段。再生盆地于印支－燕山期闭合并造山。     

西秦岭造山带泥盆纪沉积地质学和动力沉积学研究:古地理、地层层序及构造演化

晚加里东到早海西期,西秦岭北带存在一较大规模的造山带,泥盆纪的古地形呈北高南低的特下。持续的海侵由南向北侵进。中泥盆世由于北秦岭造山带的向南爷冲,形成同造山的前陆拗陷盆地。南秦岭裂陷槽是早古生代小洋盆的残余海槽。     

华北地块南部晚古生代—三叠纪盆山耦合关系

华北地块南部的晚古生代至中生代初期发育有多种类型的沉积盆地,其形成演化直接受控于秦岭造山带的主造山作用过程,泥盆纪－石炭纪是岭与华北地块的点接触碰撞时期,古秦岭洋和二郎坪弧后盆地同期逐步消亡,深化为陆壳基础上的残余海盆地及残余弧后盆地,二叠为面接触碰撞阶段,豫西小秦岭岭段首先隆升,成为向北的物源区,在商丹－北淮阳主缝合带及其弧后残余盆地消亡的同时,华北地块南部形成盆地,并成为旱二叠世华北陆表海的沉积中心,秦岭与华北地块全面碰撞发生于三叠纪,在造山变质变形广泛活动的背景下,华北地块则形成了统一的大型坳陷型盆地。     

The Carboniferous at the Northern Foot of the Dabie Mountains and Its Tectonic Implications

In the Qinling orogenic belt. oceanic crust originated in the Early Palaeozoic. while the product of conti-nental collision appeared as late as after the Triassic. The Late Palaeozoic records there are of major impor-tance for understanding the tectonic regime at that time. The Carboniferous and even Permian sequences andthe distribution of sedimentary facies in northern Huaiyang indicate that the rocks were formed in a large basinopening towards the south. Regional stratigraphic correlation shows that the interior of the Qinling orogenicbelt was a sea trough lying between the Yangtze and North China plates in the middle part of the LatePalaeozoic. With subsequent northward migration of the South China Sea, the two seas were connected witheach other. Both the melanges and the Dabie block ia the eastern sector of the Qinling belt were formed in theMesozoic ?.     

华北陆块南缘汝阳群次火山岩SHRIMP锆石U-Pb年龄及其地质意义

华北陆块南缘汝阳群下部的次火山岩一直被看作是与汝阳群同时代的火山喷发夹层。通过研究测得玄武岩SHRIMP锆石U-Pb年龄为213.5±2.4Ma,并在邻近该次火山岩层上部的紫红色泥岩中发现了褪色的角岩化现象,说明该火山岩是晚三叠世沿汝阳群下部顺层侵入的次火山岩岩床。通过对该次火山岩岩石及其地球化学特征的研究,认为该次火山岩起源于有早期俯冲洋壳或陆壳参与再循环的大陆富集型地幔的部分熔融,它与秦岭造山带几乎同时代形成的超高压榴辉岩、埃达克质岩石、高钾钙碱性花岗岩、环斑花岗岩等共同揭示了秦岭造山带自中三叠世全面碰撞造山之后,由碰撞挤压逐渐转变为伸展拉张的深部动力学过程。     

Tectonic evolution of a composite collision orogen: An overview on the Qinling–Tongbai–Hong'an–Dabie–Sulu orogenic belt in central China

The formation of collisional orogens is a prominent feature in convergent plate margins. It is generally a complex process involving multistage tectonism of compression and extension due to continental subduction and collision. The Paleozoic convergence between the South China Block (SCB) and the North China Block (NCB) is associated with a series of tectonic processes such as oceanic subduction, terrane accretion and continental collision, resulting in the Qinling–Tongbai–Hong'an–Dabie–Sulu orogenic belt. While the arc–continent collision orogeny is significant during the Paleozoic in the Qinling–Tongbai–Hong'an orogens of central China, the continent–continent collision orogeny is prominent during the early Mesozoic in the Dabie–Sulu orogens of east-central China. This article presents an overview of regional geology, geochronology and geochemistry for the composite orogenic belt. The Qinling–Tongbai–Hong'an orogens exhibit the early Paleozoic HP–UHP metamorphism, the Carboniferous HP metamorphism and the Paleozoic arc-type magmatism, but the three tectonothermal events are absent in the Dabie–Sulu orogens. The Triassic UHP metamorphism is prominent in the Dabie–Sulu orogens, but it is absent in the Qinling–Tongbai orogens. The Hong'an orogen records both the HP and UHP metamorphism of Triassic age, and collided continental margins contain both the juvenile and ancient crustal rocks. So do in the Qinling and Tongbai orogens. In contrast, only ancient crustal rocks were involved in the UHP metamorphism in the Dabie–Sulu orogenic belt, without involvement of the juvenile arc crust. On the other hand, the deformed and low-grade metamorphosed accretionary wedge was developed on the passive continental margin during subduction in the late Permian to early Triassic along the northern margin of the Dabie–Sulu orogenic belt, and it was developed on the passive oceanic margin during subduction in the early Paleozoic along the northern margin of the Qinling orogen.Three episodes of arc–continent collision are suggested to occur during the Paleozoic continental convergence between the SCB and NCB. The first episode of arc–continent collision is caused by northward subduction of the North Qinling unit beneath the Erlangping unit, resulting in UHP metamorphism at ca. 480–490 Ma and the accretion of the North Qinling unit to the NCB. The second episode of arc–continent collision is caused by northward subduction of the Prototethyan oceanic crust beneath an Andes-type continental arc, leading to granulite-facies metamorphism at ca. 420–430 Ma and the accretion of the Shangdan arc terrane to the NCB and reworking of the North Qinling, Erlangping and Kuanping units. The third episode of arc–continent collision is caused by northward subduction of the Paleotethyan oceanic crust, resulting in the HP eclogite-facies metamorphism at ca. 310 Ma in the Hong'an orogen and low-P metamorphism in the Qinling–Tongbai orogens as well as crustal accretion to the NCB. The closure of backarc basins is also associated with the arc–continent collision processes, with the possible cause for granulite-facies metamorphism. The massive continental subduction of the SCB beneath the NCB took place in the Triassic with the final continent–continent collision and UHP metamorphism at ca. 225–240 Ma. Therefore, the Qinling–Tongbai–Hong'an–Dabie–Sulu orogenic belt records the development of plate tectonics from oceanic subduction and arc-type magmatism to arc–continent and continent–continent collision.