雅鲁藏布江中游不同地表输沙量特征

雅鲁藏布江河流宽谷区是青藏高原风沙活动最为强烈地区之一.输沙量是评价区域风沙活动的最主要指标之一,但目前对该地区输沙量的研究几乎是空白.利用旋转多路方口集沙仪对雅鲁藏布江流域中游河岸沙地、河漫滩沙地和山麓沙地3种地表类型、6个点2020年9-12月的输沙量进行野外实地观测,对比不同下垫面的输沙量,分析地表特征对输沙量的...     

Petrology and Geochemistry of Post-Collisional Early Miocene Volcanism in the Karacada? Area (Central Anatolia, Turkey)

Early Miocene (ca.?21–18 Ma) volcanism in the Karacada? area comprises three groups of volcanic rocks: (1) calcalkaline suite (andesitic to rhyolitic lavas and their pyroclastics), (2) mildly-alkaline suite (alkali basalt, hawaiite, mugearite, benmoreite and trachydacite), and (3) a single trachyandesitic flow unit. Field observations, 40Ar/39Ar ages and geochemical data show that there was a progressive temporal transition from group 1 to 3 in a post-collisional tectonic setting. The calcalkaline suite rocks with medium-K in composition resemble those of subduction-related lavas, whereas the mildly-alkaline suite rocks having a sodic tendency (Na2O/K2O=1.5–3.2) resemble those of within-plate lavas. Incompatible element and Sr-Nd isotopic characteristics of the suites suggest that the lithospheric mantle beneath the Karacada? area was heterogeneously enriched by two processes before collision: (1) enrichment by subduction-related processes, which is important in the genesis of the calcalkaline volcanism, (2) enrichment by small degree melts from the astenosphere, which dominates the mildly alkaline volcanism. Perturbation of the enriched lithosphere by either delamination following collision and uplift or removal of the subducted slab following subduction and collision (i.e., slab breakoff) is the likely mechanism for the initiation of the post-collision volcanism.     

A New Genus and Species of Damsel-Dragonfly (Odonata: Isophlebioidea: Campterophlebiidae) in the Middle Jurassic of Inner Mongolia, China

The campterophlebiid new genus and species Ctenogampsophlebia reni is described from the Middle Jurassic of Inner Mongolia, China. It shows close similarities with the Lower to Middle Jurassic genera Gampsophlebia, and Petrophlebia, with closed and short subdiscoidal cells, confirming the attribution of these two other genera to the Campterophlebiidae.     

Petrogenesis of the ü?kap?l? Granitoid and its Mafic Enclaves in Elmal? Area (Ni?de, Central Anatolia, Turkey)

The Late Cretaceous ükapili Granitoid including mafic microgranular enclaves intruded into metapelitic and metabasic rocks, and overlain unconformably by Neogene ignimbrites in the Ni de area of Turkey. It is mostly granite and minor granodiorite in composition, whereas its enclaves are dominantly gabbro with a few diorites in composition. The ükapili Granitoid is composed mainly of quartz, K-feldspar, plagioclase, biotite, muscovite and minor amphibole while its enclaves contain mostly plagioclase, amphibole, minor pyroxene and biotite. The ükapili Granitoid has calcalkaline and peraluminous (A/CNK= 1.0-1.3) geochemical characteristics. It is characterized by high LILE/HFSE and LREE/HREE ratios ((La/Lu) N = 3-33), and has negative Ba, Ta, Nb and Eu anomalies, resembling those of collision granitoids. The ükapili Granitoid has relatively high 87Sr/86Sr (i) ratios (0.711189-0.716061) and low εNd (t) values (-5.13 to -7.13), confirming crustal melting. In contrast, the enclaves are tholeiitic and metaluminous, and slightly enriched in LILEs (K, Rb) and Th, and have negative Ta, Nb and Ti anomalies; propose that they were derived from a subduction-modified mantle source. Based on mineral and whole rock chemistry data, the ükapili granitoid is H-(hybrid) type, post-collision granitoid developed by mixing/mingling processes between crustal melts and mantle-derived mafic magmas.     

Dinarides东南部跨界岩溶含水层的特性

Dinarides南部是世界上岩溶发育最强烈的地区之一,同时也是欧洲降水量最大的地区。区内碳酸盐岩沉积厚度大于300m,平均岩溶发育深度从250m 至350m,沿断裂发育的岩溶,甚至更深。地下水平均流速变化较大,从0.002 cm/s至55.2cm/s。地下水滞留时间很短,水位变化非常迅速,变幅高达312m。地下水位对强降雨的响应小于4小时。岩溶大泉的主要特征是管道出口深,最大最小流量变化大。区内发育的落水洞有成千上百个,其中一些落水洞排水能力超过100m3/s,规模巨大并被洪水暂时淹没的岩溶坡立谷闻名世界各地。泉水天然流量和野生动物生存环境的改变,特别是当地特有物种的破坏,已经成为新近许多岩溶工程项目的焦点议题。由于该区极其复杂的水文地理和政治环境,不同国度间的跨界含水层似乎是一个非常敏感的问题。      

RECORD OF BLOCK ROTATION AND MAGNETIC FIELD REVERSALS IN THE TETHYAN HIMALAYA (HIDDEN VALLEY, CENTRAL NEPAL)

RECORD OF BLOCK ROTATION AND MAGNETIC FIELD REVERSALS IN THE TETHYAN HIMALAYA (HIDDEN VALLEY, CENTRAL NEPAL)