中国大陆南缘不活动大陆边缘和拉裂盆地

中国大陆南缘经历了太平洋板块和特提斯板块与欧亚板块会聚作用的复杂过程,并在不晚于早第三纪早期,已经由活动的大陆边缘转换为不活动的,具有典型的不活动边缘的重力效应特征。根据构造演化分析,大陆南缘的陆缘盆地属不活动边缘拉裂盆地,南海中央海金则属于边缘海盆地。本文阐述了亚洲大陆南缘的主要转换断裂系统,讨论了这些断裂系统所反映的太平洋—特提斯板块和欧亚板块之间板块边界的应力机制和活动方式,认为在特提斯—印度洋域,这些转换断裂系统从西向东延伸,分别属于右旋和左旋滑移。它们对中国大陆南缘边缘构造带和含油气盆地的形成和地质演化起着重要的作用。     

中国南方大地构造演化及其对油气的控制

按照板块构造理论及活动论、阶段论的思想，大致以中晚三叠世为界，将中国南方自震旦纪以来大地构造演化历史划分成海相盆地演化阶段（Z－T2）及陆相盆地演化阶级（T3－Q）两大阶段；又可进一步细分为扬子克拉通及其周缘裂谷盆地（Z－1q)、裂谷－克拉通－被动大陆边缘盆地（1c-O1）、被动陆缘－克拉通－前陆盆地（O2－S）、加里东运动（S末）、裂谷－克拉通盆地（D－T1）、克拉通残留海盆－弧后（浊积）盆地（T2）、印支运动（T2－T3）、华北－华南板块焊合、古特提斯封闭与前陆盆地的形成（T3－J2）、压扭背景下的改造作用及拉分盆地的形成（J3－K1）、伸展－裂陷盆地的形成（K2－E）、喜马拉雅运动（E末－N初）及披盖性构造层的形成（N－Q）12个阶段。特别是对南方自中晚三叠世以来的大地构造演化及其对现存油气的控制作用进行了系统研究，提出了晚侏罗世－早白垩世燕山运动对南方中生界、古生界原生油气藏的保存与破坏起到了决定性作用及燕山、喜马拉雅运动控制了现今南方原生、次生及再生烃（二次生烃）油气藏分布的新观点。     

SHRIMP U-Pb geochronology of the zircons from the Precambrian basement of the Qilian Block and its geological significances

Origin and tectonic evolution of the Qilian Precambrian basement on NW China were investigated using zircon U-Pb ages with collaborating stratigraphic and paleontological evidence. Zircon grains were separated from two schists, two granitic gneisses and one mylonized gneiss and dated with SHRIMP. Seventy percent of sixty-one detrital zircon ages from two schists ranges from 0.88 Ga to 3.09 Ga, mostly within 1.0 Ga to 1.8 Ga with a peak at 1.6 Ga to 1.8 Ga, and twenty percent varies from 2.0 Ga to 2.5 Ga. A few falls in the Archean and Neoproterozoic periods. The two granitic gneisses were dated 930±8 Ma and 918±14 Ma, whereas the mylonized granitic gneiss was dated 790±12 Ma. These ages represent two periods of magmatisms, which can be correlated with the early and late stages of magmatisms associated with the Jinningian movement on the Yangtze Blocks. The results from this and previous studies indicate that the ages of the Precambrian detrital zircons from the Qilian Block are widely distributed in the Proterozoic era, distinct from the North China Block which was stable in the Neo-Mesoproterozoic era. By contrast, the age histograms of the detrital zircons from the Qilian Block is similar to those from Precambrian basement of the Yangtze Craton. Therefore, it is suggested that the Qilian Block had a strong affinity toward the Yangtze Craton and might belong to the supercontinent Gondwana in the Neoproterozoic time. This inference is supported by Nd model age (TDM), stratigraphic, and paleontological evidence. It is further considered that the Qilian Block was rifted from the supercontinent Gondwana during late Sinian to form an isolated continent in the Proto-Tethyan Ocean, moving towards the Alaxa Block in the North China Craton. The part of Proto-Tethyan Ocean between the Qilian and Alaxa Blocks should correspond to the so-called Paleo-Qilian Ocean. Following the closure of the Paleo-Qilian Ocean in the early Paleozoic, the Qilian Block collided with the Alaxa Block to form the North Qilian Orogenic Belt. Based on this tectonic explanation, the North Qilian ophiolites should represent parts of lithosphere from the Proto-Tethyan Ocean. Lithological and geochronological evidence also indicates that the Qilian Block underwent continental reactivation possibly induced by the deep northward subduction of the North Qaidam Block in early Paleozoic time.     

华北板块北缘中段新太古代的陆-陆碰撞事件: 来自合教S型花岗岩的证据

通过对内蒙古达茂旗合教地区具有明显构造意义的新太古代S型花岗岩的主量元素、微量元素及SHRIMP锆石U-Pb年代学的研究, 为揭示华北板块北缘新太古代末的构造环境提供了进一步的证据。合教花岗岩的主量元素特征表明它是高分异的强过铝 S 型花岗岩; 其里特曼指数 σ为0. 54 ～0. 57, 属于低钾钙碱性岩石。稀土元素总量为 243. 8 ～427. 1 μg/ g。球粒陨石标准化分配模式显示 LREE 相对富集, HREE 相对亏损; ( La/ Yb)_N为 14. 88～18. 18, Eu 具有较大的负异常( Eu*/ Eu = 0. 31 ～0. 65); 模式图总体呈一右倾的海鸥型。微量元素显示Nb, Ta, Zr, Hf, Ti 等高场强元素相对亏损。合教花岗岩的微量元素组成表明其来源于正常厚度的大陆地壳, 形成于低压高温的后碰撞环境, 相当于澳大利亚拉克伦造山带的S型花岗岩。合教花岗岩的SHRIMP锆石U-Pb年龄为2556±8Ma, 属于新太古代晚期。合教强过铝 S型花岗岩反映在新太古代晚期华北板块北缘中段可能发生了一次陆-陆碰撞事件, 也表明固阳地区同时期的赞岐岩可能形成于后碰撞环境而非板片消减带。     

Occurrence of Neoproterozoic low-grade metagranite in the western Beihuaiyang zone,the Dabie orogen

Based on detailed field investigations and petrographic observations, we discovered Neoproterozoic-emplaced granite from the metavolcanics of the Dingyuan Formation in the western Beihuaiyang zone, the Dabie orogen. This study reports the results of zircon U-Pb dating and preliminary petrographic observations on two metagranite samples. The studied rocks experienced epidote-amphibolite facies metamorphism and strong structural deformation. Their U-Pb ages are 726 ± 6 and 758 ± 12 Ma, respectively, similar to those for the Luzhenguan complex in the eastern segment of the Beihuaiyang zone. In combination with previously determined 635 ± 5 Ma low-grade metagabbro, this study suggests the occurrence of at least two types of Neoproterozoic intrusive rocks in the Beihuaiyang zone, the northern margin of the South China Block (SCB): 726–758 Ma metagranite and 635 Ma metagabbro. These rocks occur within the metamorphosed Ordovician volcanic zone (originally named the Dingyuan Formation) and are in tectonic contact to each other, but they formed in different tectonic settings. The protolith ages for the Neoproterozoic low-grade metaigneous rocks are in good agreement not only with ages for two episodes of mid- and late-Neoproterozoic mafic and felsic magmatism in the Suizhou and Zaoyang area, Hubei Province, but also agree with protolith ages of ultrahigh-pressure metaigneous rocks in the Dabie-Sulu orogenic belt. In view of their tectonic relationships to country rocks, it appears that these Neoproterozoic low-grade rocks are exotic and they may have been detached and scraped from subducting SCB crust in the early Triassic during the initial continental subduction, and thrusted over Paleozoic metamorphosed rocks in the southern margin of the North China Block during continental collision.     

Zircon SHRIMP U-Pb dating for olivine gabbro at Wangmuguan in the Beihuaiyang zone and its geological significance

In the Neoproterozoic, a large-scale magmatic activ- ity took place in the northern margin of the South China Block, with ages in a range of 700―800 Ma[1―4]). A systematic zircon U-Pb dating for bimodal metaigneous rocks in the Dabie-Sulu orogen yields ages of 758 ± 15 Ma[5], typifying rift magmatism along the northern margin of the South China Block during the middle Neoproterozoic. In addition, there is a widespread oc- currence of volcanic tuff interlayers around 635 Ma with the se…     

中祁连北缘野牛沟-托勒地区晋宁期花岗岩的地质意义

阐述了在中祁连陆块北缘野牛沟-托勒地区原划分的古元古代托赖（岩）群中识别并划分出了晋宁期片麻状花岗岩。它侵位于中元古代中浅变质岩系湟中群以及新解体出的中-新元古代托勒片岩中,单颗粒锆石铀-铅同位素年龄为（837．8±58）Ma、（842±37）Ma,表明它们是晋宁期岩浆事件的产物,地球化学特征显示形成于碰撞构造环境;该片麻状花岗岩的发现,对于祁连造山带前震旦纪基底的深入研究及更进一步确定该地区存在的晋宁期碰撞造山作用提供了直接证据。     

鄂尔多斯南部地区早古生代被动大陆边缘特征与演化

鄂尔多斯南部地区早古生代被动大陆边缘特征与演化@袁卫国@赵一鸣...     

北祁连直河蛇绿岩的地质和地球化学特征

直河蛇绿岩是在北祁连造山带中新发现的,该蛇绿岩由地幔橄榄岩、辉长辉绿岩、玄武岩、硅质岩等组成,以构造岩片为接触关系.蛇绿岩中岩石地球化学特征表明,该蛇绿岩具有大洋拉斑玄武岩的特征,同时具有某些岛弧特征,基性岩类的REE球粒陨石标准化配分模式为平坦型和LREE亏损型,超基性岩为亏损地幔源和富集地幔物质加入的混合成因,稀土分配型式不同于典型洋脊玄武岩,源区为亏损地幔和富集地幔的混合源.北祁连自寒武纪末大陆裂解,完成大陆裂陷向洋盆的转化,至奥陶纪形成沟弧盆体系.直河蛇绿岩属于弧后盆地扩张环境的产物.     

Discovery of Late Carboniferous strata and their tectonic significance in the southern margin of the North China Block （Huoqiu and Gushi areas）

Late Carboniferous fossils （such as Boultonia？ sp., Tabulata, and spiriferoid specimens with smooth she/Is）, bioclastic material （such as crinoid stems and sponge fragments）, and Late Ordovician microfossils of the conodont Belodina have been discovered in the lower part of the strata typically referred to as the Neoproterozoic on the boundary of the provinces of Anhui and Henan in the southern margin of the North China Block. These findings prove that the strata contain macrofossils belonging to the Late Carboniferous, which belonged to a carbonate debris flow deposit that was formed under a carbonate slope environment. The conodont fossils might belong to a detrital deposit. Thus, it is possible to reset the stratigraphic sequences and tectonic attributes belonging to the North Huaiyang tectonic belt and limit the Shouxian fault to the boundary between the Dabie Orogen and North China Block.