新疆塔里木盆地东北部库鲁克塔格地区寒武─奥陶纪遗迹化石

本文研究的遗迹化石采自新疆塔里木盆地东北部库鲁克塔格山上寒武统和奥陶系．经鉴定计有１６个遗迹属，２１个遗迹种，其中有４个新遗迹种．这个地区丰富的深海Ｎｅｒｅｉｔｅｓ遗迹相遗迹化石在我国首次发现，这些发现对于塔里木盆地的油气勘探，沉积环境分析具有重要的意义．     

新构造运动对阿尔泰山及萨吾尔山山前带地下水的控制

虽山前带第四系很薄,但由于新构造运动掀斜作用及断裂的贯通作用,构造盆地第三系含水层与山前带地下水产生水力联系并获得很高的压力水头.山前带第四系厚度小的原因,是中更新世以后上升幅度增大,早中更新世沉积遭受强烈剥蚀.由于第四系很薄,曾长期被人认为地下水贫乏.但据勘探证实,较大冲积扇有丰富的潜水资源.     

南迦巴瓦峰西北坡末次冰期以来的冰川变化

本区自晚更新世以来的冰川变化可分为距今25000—10000年的末次冰期、距今3500—1000年的新冰期和距今400—200年的小冰期,冰川面积逐次减小,雪线上升,与气候变化具同步性。     

Limestone assimilation by basaltic magmas: an experimental re-assessment and application to Italian volcanoes

The results of an experimental study of limestone assimilation by hydrated basaltic magmas in the range 1,050–1,150°C, 0.1–500 MPa are reported. Alkali basalts doped with up to 19 wt% of Ca, Mg-carbonates were equilibrated in internally heated pressure vessels and the resulting phase relationships are described. The major effects of carbonate incorporation are: (1) generation of CO₂-rich fluid phases; (2) change in liquidus phase equilibria; the crystallization of Ca-rich clinopyroxene is favored and the other phases (e.g. olivine, plagioclase), present in the absence of carbonate assimilation, are consumed. As a consequence of the massive clinopyroxene crystallization, the residual melt is strongly silica-depleted and becomes nepheline-normative. Compositional and mineralogical evolutions observed in Mt. Vesuvius eruptive products match those documented in our experiments with added carbonates, suggesting the possibility that carbonate assimilation increased during the last 25 ka of activity. In Central-Southern Italy, carbonate assimilation at shallow levels probably superimposes on deeper source heterogeneities.     

甘肃玉门马鬃山以北矿区矿坑水合理开发利用探讨

甘肃玉门马鬃山以北矿区位于河西走廊以北的残山丘陵及丘间盆地,距玉门市300余公里。这里环境脆弱,荒漠（主要为岩漠）化严重。地表为冲洪积、坡积和风积砂砾石、角砾土、砂及粘性土等,残山和残丘为华力西期侵入岩。侵入岩中储藏铁矿和金矿。这里降水量仅50mm左右;而蒸发量达3000mm以上。这里在矿山开发中将矿坑水任意排放,任其蒸发而损失。笔者在本区工作后认为：应重视地下水的重复利用,其一是将矿坑水排放于废弃矿井中,使用时在抽出;其二是将矿坑水排放于废渣中,做好渗滤层和集水池,上部做好防蒸发装置。     

龙首山成矿带芨岭北东向深大隐伏断裂构造存在的佐证

龙首山成矿带是我国著名的镍、铁、铜、铀等多金属矿产地,北西向断裂作为铀矿控矿构造特征明显。为了查清芨岭北东向隐伏深大断裂是否存在,综合分析研究区的磁场、重力场和遥感影像特征,识别出芨岭北东向的深大断裂,认为该断裂属于早期的深大断裂,晚期复活错断了北西向断裂,北东向与北西向深大断裂交汇处是铀成矿的有利靶区。这一结论可能为该区深部找矿提供参考。     

江西武功山热穹隆变质--岩浆作用及演化

处于扬子与华夏古板块加里东期拼贴带的武功山热穹隆,以造山期变形花岗岩为中心,南华一寒武系遭受绿片岩相一低角闪岩相变质并形成变质矿物分带,环绕岩体分布,与中生代以来伸展形成的脆性断裂系统构成外环,共同组合形成屹立于晚古生代地层分布区的穹隆状构造。在区域递增变质带基础上,造山早期,深部初始重熔岩浆与深埋的变质岩发生交代形成原地型英云闪长质“混染岩浆”,岩浆上浸过程中,活动组分不断作用于围岩,致使围岩的成分、结构构造产生重新调整,形成岩体边缘混合岩。同时,由于硅铝质围岩组分加入,酸度增加,而渐变过渡为花岗闪长质岩浆。造山晚期,进一步演化为岩浆型正常花岗岩,并呈套叠状侵入于早期岩体之中。从早到晚构成同源岩浆演化系列,并发育明显构造应力变形。热穹隆区加里东期形成递进渐增变质一岩体边缘混合一变形花岗岩“三位一体”分布格局。中生代伸展一岩浆作用的复合叠加,进一步强化了热穹隆的构造背景。大致在旱白垩世末基本定型。     

Architecture of a Palaeoproterozoic Rift System: Evidence from the Fiery Creek Dome region,Mt Isa terrane

The Mt Isa Rift Event is a Palaeoproterozoic intracontinental extension event that defines the beginning of sedimentation into the Isa Superbasin in the Western Fold Belt, Mt Isa terrane. In the mildly deformed Fiery Creek Dome region, on the northwest flanks of the Mt Isa Rift, elements of the Mt Isa Rift Event rift architecture are preserved without being intensely overprinted by later deformation. In this region two discrete generations of northwest‐dipping normal faults have been identified. Early generation normal faults were active during the deposition of fluvial and immature conglomerate and sandstone of the Bigie Formation. Renewed rifting and the development of late‐generation normal faults occurred during deposition of shallow‐marine sandstone and siltstone of the lower Gunpowder Creek Formation. Differential uplift between tilt blocks formed an array of spatially and temporally discontinuous synrift unconformities on the crests of uplifted tilt blocks. Applying the domino model yields ～28% crustal extension for the entire Mt Isa Rift Event. Northwest‐striking transverse faults facilitated differential displacement along normal faults and formed boundaries to normal fault segments, creating smaller depositional compartments along half‐graben axes. Three large domes were formed during laccolith emplacement. These domes produced palaeogeographical highs that divided the region into sub‐basins and were a source for the coarse fluvial synrift sequences deposited during the early Mt Isa Rift Event. The basin architecture in the Fiery Creek Dome region is consistent with northwest‐southeast‐directed extension.     

Lamprophyric intrusions of probable carbonatitic affinity from South Australia

Primary carbonate‐bearing lamprophyric rocks have been recognised in the Walloway Diapir, South Australia. Their petrography and trace‐element geochemistry indicates that they have carbonatitic affinities. The rocks are magnetic and can be detected by ground magnetometer surveys.     

New SHRIMP geochronology for the Western Fold Belt of the Mt Isa Inlier: developing a 1800 – 1650 Ma event framework ∗

The integration of detrital and magmatic U – Pb zircon SHIRMP geochronology with facies analysis has allowed the development of a chronostratigraphic framework for the Leichhardt and Calvert Superbasins of the Western Fold Belt, Mt Isa Inlier. This new event chart recognises three supersequences in the Leichhardt Superbasin: the Guide, Myally and Quilalar Supersequences. The Guide Supersequence spans the interval ca 1800 – 1785 Ma and includes the Bottletree Formation and the Mt Guide Quartzite. Sequence relationships suggest that this sedimentary package represents an asymmetric second-order cycle, recording a thickened transgressive suite of deposits and a comparatively thin second-order highstand. The overlying Myally Supersequence spans the interval ca 1780 – 1765 Ma and includes the Eastern Creek Volcanics and syndepositional Lena Quartzite, and the Myally Subgroup. This package represents a second-order supersequence cycle in which mafic volcanism was initiated during a phase of east – west extension. Following the cessation of volcanism, transgression led to the deposition of the Alsace Quartzite and deeper water Bortala Formation. An increase in the rate of sediment supply over accommodation resulted in progradation and deposition of the Whitworth Quartzite and redbed playa facies of the Lochness Formation as accommodation closed. The Quilalar Supersequence spans the interval ca 1755 – 1740 Ma. Sequence analysis in the eastern part of the Leichhardt River Fault Trough identifies a transgressive suite of facies at the base of this supersequence. Black shales from the upper part of the transgressive deposits characterise the condensed section for this supersequence. Facies analysis indicates that deposition took place in a series of storm-, tide- and wave-dominated shelfal marine depositional systems. Although there are no new depositional age constraints for the younger Bigie Formation, field relationships suggest that it is coeval with, or immediately preceded, the ca 1710 Ma Fiery magmatic event. Therefore, a separate supersequence is defined for the Bigie Formation, the Big Supersequence, even though it may be more genetically related to the Fiery magmatic event. The Big Supersequence, together with the ca 1690 Ma Prize Supersequence, comprise the Calvert Superbasin. The evolution of the Leichhardt and Calvert Superbasins are temporally and spatially related to magmatism. In particular, the new maximum depositional ages for the Guide and Myally Supersequences refine the age of the Eastern Creek Volcanics to ca 1780 – 1775 Ma. The new age for the Weberra Granite is within error of the age for the Fiery Creek Volcanics, indicating that they are both part of the ca 1710 Ma Fiery event. New ages for the Sybella Granite confirm that magmatism associated with this magmatic event is refined to 1680 – 1670 Ma, and is followed by deposition of the Gun Supersequence. Combining the new geochronological constraints with previous work now provides a detailed stratigraphic event framework between 1800 and 1575 Ma for the Western Fold Belt of the Mt Isa Inlier, and allows detailed comparisons and correlations with the Eastern Fold Belt and other Proterozoic terranes.