东亚大陆边缘的构造格架及其中-新生代演化   总被引：10，自引：0，他引：10  

吴根耀  矢野孝雄 《地质通报》2007,26(7):87-800

燕山运动在亚洲大陆雏形东缘形成2条北东向的剪切带:郯庐断裂带和长乐-南澳-中央构造线断裂带,晚侏罗世—古近纪早期沿之发生地体/地块的拼贴。系统叙述了各移置地体/地块的主要岩石记录和拼贴时代,据起源分为3类:异地的(包括源自冈瓦纳的和源自盘古大洋的)、半异地的和准原地的;据拼贴位置分为2组:拼贴后基本位于原地的(日本海张开以前) 和发生过向北东错移的。新生代内东亚大陆边缘发生解体,可以台湾岛以北的菲律宾海盆断裂为界将东亚大陆边缘弧分为2段,北段仍处于剪切-拉张中,南段已进入剪切挤压-造山阶段。强调该地区中—新生代演化经历了2个里丁旋回, 形成早白垩世的北东向和新近纪的北东东向2期新生构造。  相似文献   

Early Cretaceous volcanic rocks and Early Cenozoic extrusions of Cape Mary, Schmidt Peninsula, north Sakhalin: Geochemical study     

V. P. Simanenko  S. V. Rasskazov  T. A. Yasnygina  A. I. Malinovskii  A. A. Chashchin 《Russian Journal of Pacific Geology》2007,1(3):265-275

The Early Cretaceous volcanic rocks of the Mariisky sequence and Early Cenozoic extrusive-vent rocks of Cape Mary are exposed at the northwestern extremity of Schmidt Peninsula, north Sakhalin. In chemical composition, all the rocks are subdivided into four groups. Three groups include the volcanic rocks of the Mariisky sequence, which consists, from bottom to top, of calc-alkaline rocks, transitional calc-alkaline-tholeiite rocks, and incompatible element-depleted tholeiites. These rocks show subduction geochemical signatures and are considered as a fragment of the Moneron-Samarga island arc system. Trace-element modeling indicates their derivation through successive melting of garnet-bearing mantle and garnet-free shallower mantle sources containing amphibole; pyroxene; and, possibly, spinel. The mixed subduction and within-plate characteristics of the extrusive vent rocks of Cape Mary attest to their formation in a transform continental margin setting.  相似文献   

Heavy clastic minerals from the Far East island-arc complexes     

A. I. Malinovsky  P. V. Markevich 《Russian Journal of Pacific Geology》2007,1(1):71-81

The results of the study of heavy clastic minerals from the Cretaceous-Paleogene terrigenous complexes of Sikhote-Alin and Kamchatka, as well as from the Cenozoic sediments of the deepwater Vanuatu Trench, are summarized. The data obtained have been interpreted on the basis of their comparison with heavy mineral assemblages of recent sediments deposited in known geodynamic settings. It is shown that the heavy clastic minerals of sedimentary rocks, their relative quantities, and chemical compositions may serve as reliable indicators of different island-arc settings and magmatic processes; these indicators may also be used for identification of such settings in paleobasins of orogenic regions.  相似文献   

近50a来桂林市灰霾天气的气候特征及热岛效应影响     

唐伍斌 《广西气象》2007,28(4):20-21,25

根据桂林基准站1957～2006年的观测资料,对桂林市灰霾天气的年、季变化规律及与热岛效应的关系进行了分析。结果表明,桂林市年灰霾日数平均值为30d,80年代前年灰霾日数变化相对平稳,年平均值为8.6d,处于较低水平,80年代后灰霾日数年平均值为49d,比80年代前增加了40.4d,年平均灰霾日数呈明显的线性增长趋势;灰霾日数的月季变化表现为秋冬季多,春夏季少的分布特征,秋冬两个季节的灰霾日数占全年的76%;90年代后桂林出现热岛效应,第四季度尤为明显,与灰霾天气也大多出现在这个季节的分析结果一致。  相似文献   

城市下垫面反照率变化对北京市热岛过程的影响——个例分析   总被引：13，自引：1，他引：13  

江晓燕  张朝林高华　苗世光 《气象学报》2007,65(2):301-307

随着城市的不断发展,城区地表反照率等下垫面物理特征和属性会发生明显的变化,进而会对城市热岛等大气环境形成影响。文中使用中国气象科学研究院开发的新一代数值天气预报模式(GRAPES),针对2004年10月北京一次重空气污染事件中的典型城市热岛过程,分别设计了两种数值试验方案:(1)对照试验,使用模式缺省的城区下垫面反照率参数,取值0.18;(2)敏感性试验,参考同期中国科学院大气物理研究所铁塔280m高度下垫面反照率观测事实,将北京区域城市类型下垫面反照率减小至0.15。通过对比两种试验方案在1km水平分辨率下的24h模拟结果,研究了城市下垫面反照率变化对北京地区城市热岛过程的影响。结果表明:(1)GRAPES模式可成功模拟此次热岛过程中城区和郊区近地面温度的日变化趋势;(2)城市下垫面反照率的变化对城市热岛的发展非常重要,城市反照率下降0.03会使城市热岛强度增强0.8℃左右,结果也更接近实况。这说明随着城市发展引起的地表反照率减小有利于城市热岛强度增加;(3)通过分析地表的长波辐射发现,在城市区域较小反照率情形下,城区的长波辐射始终比郊区大,有利于热岛的形成;同时也有利于城区近地层的风场辐合增加,对此次污染过程的发展是有利的。  相似文献   

琼西北地区冰川地貌陆地卫星TM图像解译   总被引：3，自引：0，他引：3  

李邦良 《国土资源遥感》1998,9(3):90-94

在北门江流域更新世沉积广布、厚度巨大。在对区内的建筑砂矿进行成矿背景条件研中,利用了陆地卫星TM图像并与区内的地质地球物理资料进行综合分析,发现了区内的冰蚀台面、冰洼、冰斗、冰川槽谷和冰碛堤、冰碛裙和冰水扇等冰川作用遗迹。通过对冰蚀、冰碛地貌的研究发现它们之间内在的成生规律。  相似文献   

地理信息技术在地籍管理系统中的应用   总被引：6，自引：1，他引：5       下载免费PDF全文

徐世武 《地球科学》1998,23(4):424-426

利用地理信息技术实现图形数据与属性数据完美的结合,维持图形数据和属性数据的一致,可以使建立在其之上的地籍管理系统使用方便、操作直观、快速准确．  相似文献   

城市区域屋顶上与地上的风速和温度特征分析   总被引：17，自引：5，他引：12  

张一平  彭贵芬 《地理科学》1998,18(1):45-52

以低纬的城市昆明为研究对象,利用城内外屋顶上和地上的风速和温度实测资料,分析了研究较少的,做为城市第二热力面的屋顶面附近的风度温特征,变化规律及其与地上的差异,得到了一些有益的结果。  相似文献   

K–Ar ages from seamount chains in the back-arc region of the Izu–Ogasawara arc     

OSAMU  ISHIZUKA  KOZO  UTO  MAKOTO  YUASA & ALFREDG.  HOCHSTAEDTER 《Island Arc》1998,7(3):408-421

The Izu–Ogasawara arc contains, from east to west, a volcanic front, a back-arc extensional zone (back-arc knolls zone), and a series of across-arc seamount chains that cross the extensional zone in an east-northeast and west-southwest direction and extend into the Shikoku Basin. K–Ar ages of dredged volcanic rocks from these across-arc seamount chains and extension-related edifices in the back-arc region of the Izu–Ogasawara arc were measured to constrain the volcanic and tectonic history of the arc since the termination of spreading in the Shikoku Basin. K–Ar ages range between 12.5 and 1 Ma. Andesitic to dacitic rocks of 12.5–2.9 Ma occur mainly on the western part of the chains. The western part of the chains are the locus of volcanism behind the front which erupted mainly calc-alkaline andesitic lavas. The youngest rocks (< 2.8 Ma), characterized by cpx-ol basalt, occur along the western margin of the back-arc knolls zone. Basaltic rocks of 12.5–2.9 Ma have relatively high concentrations of Na₂O (> 2.0 wt%), Zr (> 50 p.p.m.) and Y (> 20 p.p.m.) and low CaO (< 12 wt%). On the other hand, basalts of 2.8–1 Ma have lower Na₂O (< 1.8 wt%), Zr (< 50 p.p.m.) and Y (< 20 p.p.m.), but significantly higher CaO (> 12 wt%). The age inferred for the initiation of back-arc rifting (∼ 2.35–2.9 Ma: Taylor 1992 ) behind the current volcanic arc coincides with the time that basalt chemistry changed drastically (eruption of the low-Na₂O and high-CaO basalt). This implies that post-2.8 Ma volcanism in the back-arc knolls zone is associated with rifting. Similarly, the change in chemical composition might be explained by a different type of source mantle following rift initiation. Volcanism in the western seamounts ceased after the onset of rifting at ∼ 2.8 Ma.  相似文献   

Arc–arc collision in the Izu collision zone, central Japan, deduced from the Ashigara Basin and adjacent Tanzawa Mountains     

WONN  SOH  KAZUO  NAKAYAMA & TAKU  KIMURA 《Island Arc》1998,7(3):330-341

The Pleistocene Ashigara Basin and adjacent Tanzawa Mountains, Izu collision zone, central Japan, are examined to better understand the development of an arc–arc orogeny, where the Izu–Bonin – Mariana (IBM) arc collides with the Honshu Arc. Three tectonic phases were identified based on the geohistory of the Ashigara Basin and the denudation history of the Tanzawa Mountains. In phase I, the IBM arc collided with the Honshu Arc along the Kannawa Fault. The Ashigara Basin formed as a trench basin, filled mainly by thin-bedded turbidites derived from the Tanzawa Mountains together with pyroclastics. The Ashigara Basin subsided at a rate of 1.7 mm/year, and the denudation rate of the Tanzawa Mountains was 1.1 mm/year. The onset of Ashigara Basin Formation is likely to be older than 2.2 Ma, interpreted as the onset of collision along the Kannawa Fault. Significant tectonic disruption due to the arc–arc collision took place in phase II, ranging from 1.1 to 0.7 Ma in age. The Ashigara Basin subsided abruptly (4.6 mm/year) and the accumulation rate increased to approximately 10 times that of phase I. Simultaneously, the Tanzawa Mountains were abruptly uplifted. A tremendous volume of coarse-grained detritus was provided from the Tanzawa Mountains and deposited in the Ashigara Basin as a slope-type fan delta. In phase III, 0.7–0.5 Ma, the entire Ashigara Basin was uplifted at a rate of 3.6 mm/year. This uplift was most likely caused by isostatic rebound resulting from stacking of IBM arc crust along the Kannawa Fault which is not active as the decollement fault by this time. The evolution of the Ashigara Basin and adjacent Tanzawa Mountains shows a series of the development of the arc–arc collision; from the subduction of the IBM arc beneath the Honshu Arc to the accretion of IBM arc crust onto Honshu. Arc–arc collision is not the collision between the hard crusts (massif) like a continent–continent collision, but crustal stacking of the subducting IBM arc beneath the Honshu Arc intercalated with very thick trench fill deposits.  相似文献