中国西北地区沉积盆地石油地质

中国近代石油工业创始于西北地区诸含油气盆地。近年来,由于国家西部大开发的发展战略,使西北地区的勘探活动又重新活跃起来。在中国西北含油气盆地内,古生界海相沉积和中、新生界陆相沉积都有生成油气的烃源岩。塔里木、准噶尔、柴达木、吐鲁番和酒泉等主要沉积盆地动力学演化史可划分为三个旋回,每一旋回都经历了由伸展到聚敛的完整演化过程。中国西北地区含油气前景看好,随着勘探工作的进展,将会在此区继续发现一些大、中型的油、气田。     

Petrogenesis of Al–silicate-bearing trondhjemitic migmatites from NE Sardinia, Italy

The migmatites from Punta Sirenella (NE Sardinia) are layered rocks containing 3–5 vol.% of centimeter-sized stromatic leucosomes which are mainly trondhjemitic and only rarely granitic in composition. They underwent three deformation phases, from D₁ to D₃. The D₁ deformation shows a top to the NW shear component followed by a top to the NE/SE component along the XZ plane of the S₂ schistosity. Migmatization started early, during the compressional and crustal thickening stage of Variscan orogeny and was still in progress during the following extensional stage of unroofing and exhumation.

The trondhjemitic leucosomes, mainly consisting of quartz, plagioclase, biotite ± garnet ± kyanite ± fibrolite, retrograde muscovite and rare K-feldspar, are locally bordered by millimeter-sized biotite-rich melanosomes. The rare granitic leucosomes differ from trondhjemitic ones only in the increase in modal content of K-feldspar, up to 25%. Partial melting started in the kyanite field at about 700–720 °C and 0.8–0.9 GPa, and was followed by re-equilibration at 650–670 °C and 0.4–0.6 GPa, producing fibrolite–biotite intergrowth and coarse-grained muscovite.

The leucosomes have higher SiO₂, CaO, Na₂O, Sr and lower Al₂O₃, Fe₂O₃, MgO, TiO₂, K₂O, P₂O₅, Rb, Ba, Cr, V, Zr, Nb, Zn and REE content with respect to proximal hosts and pelitic metagreywackes. Sporadic anomalous high content of calcium and ferromagnesian elements in some leucosomes is due to entrainment of significant amounts of restitic plagioclase, biotite and accessory phases. The rare granitic leucosomes reveal peritectic K-feldspar produced by muscovite-dehydration melting. Most leucosomes show low REE content, moderately fractionated REE patterns and marked positive Eu anomaly. Proximal hosts and pelitic metagraywackes are characterized by higher REE content, more fractionated REE patterns and slightly negative Eu anomaly.

The trondhjemitic leucosomes were generated by H₂O-fluxed melting at 700 °C of a greywacke to pelitic–greywacke metasedimentary source-rock. The disequilibrium melting process is the most reliable melting model for Punta Sirenella leucosomes.     

造山过程中的流体—岩石相互作用和质量传输的评述

在汇聚板块边缘,滑脱面的滑动和沉积岩系的逆冲堆叠,导致孔隙水被压实排出,流体润滑了脱面,从而引起增生楔的生长。流体对流体制是地壳深熔的先驱事件。碱性花岗岩在次固相下有丰富的岩浆水的出溶,并且促进了碱性长石的微组构重组织。上部地壳浅表流体的循环主要受岩浆侵位驱动。韧性剪切带Ｔｉ、Ｆｅ、Ｍｇ残留富集,Ｓｉ、Ｃａ、Ｓｒ带出,流体不混溶和相分离是Ａｕ沉淀的重要机制。断层带尤其深部断层带具有高的流体／岩石比     

Devonian-Carboniferous unconformity in Argentina and its relation to the Eo-Hercynian orogeny in southern South America

The Devonian-Carboniferous contact in southern South America, characterized by a sharp unconformity, has been related to the Late Devonian-Early Carboniferous Eo-Hercynian orogeny. The Calingasta-Uspallata basin of western Argentina and the Sauce-Grande basin (Ventana Foldbelt) of eastern Argentina have been selected to characterize this unconformity. The Eo-Hercynian movements were accompanied in western Argentina by igneous activity related to a Late Devonian—Early Carboniferous magmatic arc mainly exposed today along the Andean Cordillera. This magmatic activity is partly reflected also in eastern Argentina (Ventana Foldbelt), where isotopic dates suggest a thermal event also related to the intrusions present to the west in the North Patagonian Massif and Sierras Pampeanas. The scarcity of Lower Carboniferous deposits in the stratigraphic record of southern South America suggests that the Early Carboniferous was a time interval dominated by uplift and erosion followed by widespread subsidence during the Middle and Late Carboniferous. The origin of the Eo-Hercynian orogeny can be linked with the convergence between the Arequipa Massif, and its southern extension, and the South American continent. Its effects are best represented along the Palaeo-Pacific margin, although distant effects are discernible in the cratonic areas of eastern South America. Correspondence to: O. R. López-Gamundí     

http://www.sciencedirect.com/science/article/pii/S1674987114000334

The Musgrave Province developed at the nexus of the North,West and South Australian cratons and its Mesoproterozoic evolution incorporates a 100 Ma period of ultra-high temperature(UHT) metamorphism from ca.1220 to ca.1120 Ma.This was accompanied by high-temperature A-type granitic magmatism over an 80 Ma period,sourced in part from mantle-derived components and emplaced as a series of pulsed events that also coincide with peaks in UHT metamorphism.The tectonic setting for this thermal event(the Musgrave Orogeny) is thought to have been intracontinental and the lithospheric architecture of the region is suggested to have had a major influence on the thermal evolution.We use a series of two dimensional,fully coupled thermo-mechanical-petrological numerical models to investigate the plausibility of initiating and prolonging UHT conditions under model setup conditions appropriate to the inferred tectonic setting and lithospheric architecture of the Musgrave Province.The results support the inferred tectonic framework for the Musgrave Orogeny,predicting periods of UHT metamorphism of up to 70 Ma,accompanied by thin crust and extensive magmatism derived from both crustal and mantle sources.The results also appear to be critically dependent upon the specific location of the Musgrave Province,constrained between thicker cratonic masses.     

川西马尔康片麻岩穹隆与伟晶岩型锂矿的构造成因

片麻岩穹隆是造山折返过程形成的重要构造样式。马尔康锂矿床位于松潘-甘孜造山带腹地的马尔康片麻岩穹隆中,其核部为太阳河花岗闪长岩和可尔因花岗岩、幔部由经过变质作用的晚三叠世深海—半深海复理石和浊积岩组成,大量含锂伟晶岩脉侵位于红柱石-十字石变质带中。通过野外地质调查和构造分析,在马尔康片麻岩穹隆中识别出三期构造变形叠加于造山早期大规模收缩变形之上:第一期变形(D1)为南向的大型高温拆离剪切带(马尔康拆离断层,MRKD);第二期变形(D2)为马尔康"穹隆构造";第三期变形(D3)为后期叠加的新生代近东西向逆冲断层。新的锆石U-Pb年代学数据表明太阳河和可尔因岩体的结晶年龄分别为226～212 Ma与224～218 Ma,马尔康拆离断层中平行剪切面理的同构造变形伟晶岩脉形成于约212～207 Ma,而未变形含锂伟晶岩脉则形成于200～190 Ma之间。研究表明,马尔康片麻岩穹隆在造山早期伴随220～212 Ma的花岗岩侵位,形成中低压巴罗式变质作用;在挤压向伸展转换过程(212～207 Ma)中,形成向南剪切的拆离断层以及变质核杂岩构造,致使花岗岩浆底辟上涌和片麻岩穹隆的形成;200～190...     

Timing of orogenic events in the Lachlan Orogen

A substantial database of ⁴⁰Ar/³⁹Ar ages, collected recently from micas in western and central Victoria, has been used in several recent papers as support for continuous, diachronous deformation across western and central Victoria lasting through much of the Early Palaeozoic. This paper reviews these ages, together with field evidence collected over the last ten years. It provides an alternative interpretation, that mica growth and overgrowth in western Victoria was not continuous but episodic, occurring at ca 455 Ma, 440 Ma and 425 Ma, with little or no mica growth recorded from between these times. These ages have been obtained from mica in regional cleavage, crenulation cleavage and in quartz veins, and from across the entire width of the Stawell and Bendigo structural zones of western Victoria. A sharp change in mica ages occurs at the Mt William Fault, east of which no mica growth older than about 380 Ma is recorded. Several ages used in support for diachronous deformation are not related to deformation: an ⁴⁰Ar/³⁹Ar age of 417 Ma from Chewton is from the aureole of a Devonian granite, and an age of 410 Ma from the Melbourne Zone is shown to contain a substantial amount of inherited mica. If it is accepted that mica growth can be used to date deformation, then the ⁴⁰Ar/³⁹Ar ages indicate episodic, not continuous, deformation in western Victoria (Stawell and Bendigo Zones). The sharp decrease in the deformation age in the Melbourne Zone, east of the Mt William Fault, agrees well with field evidence that shows continuous sedimentation in the Melbourne Zone in the period (Ordovician to mid‐Early Devonian) during which the Stawell and Bendigo zones were undergoing deformation. Some correlation also exists between the ⁴⁰Ar/³⁹Ar ages from western Victoria and well‐constrained deformational events in the eastern Lachlan Orogen. The pattern of deformation has important corollaries in any model that attempts to understand what drives the deformation. While plate convergence must be the ultimate driving force, the pattern is quite inconsistent with deformation of a crust that was being drawn progressively into subduction zones, as proposed in recently published models. Rather, the observed pattern suggests that deformation happened in several very brief events, probably on semi‐rigid plates.     

大别造山带燕山期造山作用的岩浆岩石学证据

在区域地质填因基础上研究了大别地区燕山期岩浆岩，重新划分了该区燕山期岩浆作用期次，发现大别地区在燕山期存在一个完整的造山岩浆旋回。首次提出本区燕山晚期岩浆岩为双峰式组合，与燕山早期岩浆岩属高钾钙(碱)性—钾玄岩组合一起构成一个从挤压到伸展的造山岩浆旋回，成为燕山期造山的重要佐证。岩浆岩成因特点揭示出本区的岩石圈结构在燕山期存在一个从双倍陆壳到正常陆壳的过程，深部地质过程则是底侵作用和拆沉作用的继续。     

Influence of syn-sedimentary faults on orogenic structure: examples from the Neoproterozoic–Mesozoic east Siberian passive margin

The east margin of the Siberian craton is a typical passive margin with a thick succession of sedimentary rocks ranging in age from Mesoproterozoic to Tertiary. Several zones with distinct structural styles are recognized and reflect an eastward-migrating depocenter. Mesozoic orogeny was preceded by several Mesoproterozoic to Paleozoic tectonic events. In the South Verkhoyansk, the most intense pre-Mesozoic event, 1000–950 Ma rifting, affected the margin of the Siberian craton and formed half-graben basins, bounded by listric normal faults. Neoproterozoic compressional structures occurred locally, whereas extensional structures, related to latest Neoproterozoic–early Paleozoic rifting events, have yet to be identified. Devonian rifting is recognized throughout the eastern margin of the Siberian craton and is represented by numerous normal faults and local half-graben basins.Estimated shortening associated with Mesozoic compression shows that the inner parts of ancient rifts are now hidden beneath late Paleozoic–Mesozoic siliciclastics of the Verkhoyansk Complex and that only the outer parts are exposed in frontal ranges of the Verkhoyansk thrust-and-fold belt. Mesoproterozoic to Paleozoic structures had various impacts on the Mesozoic compressional structures. Rifting at 1000–950 Ma formed extensional detachment and normal faults that were reactivated as thrusts characteristic of the Verkhoyansk foreland. Younger Neoproterozoic compressional structures do not display any evidence for Mesozoic reactivation. Several initially east-dipping Late Devonian normal faults were passively rotated during Mesozoic orogenesis and are now recognized as west-dipping thrusts, but without significant reactivation displacement along fault surfaces.     

构造旋回与大地构造年表

构造旋回的划分是大地构造研究的基础之一。但板块学说兴起以来,一些学者基于均变论的哲学思想,却试图抛弃构造旋回的概念。然而,随着时间的推移,地球系统科学的提出,大规模、多学科地学观测,人们已认识到突变与灾变的重要性,认识到渐变与突变相结合的螺旋式向前发展的旋回演化论,才是更全面、更深刻地认识地质规律的有力武器。在大地构造研究中,一些学者常用地层年表,而不用构造旋回。然而,以生物地层学为主要依据的显生宙地层年表与构造旋回和构造岩浆事件并不完全耦合。这是因为,地层年表是在研究地球表生作用,即岩石圈、水圈、大气圈、生物圈之间相互作用的基础上建立的;而构造旋回则是地球内生作用,即壳、幔、核以及壳、幔、核不同层次间多层圈相互作用的历史记录。一些学者在研究大地构造时,只用同位素年龄表示的构造事件,不使用构造旋回。然而,"事件"只是单个现象的呈现,只是构造发展的片段,旋回则阐明过程,反映事物发展中各"事件"(片段)之间的内在联系,反映事物演化的本质。事实上,威尔逊旋回的建立,已为构造旋回和构造事件之间的联系赋予了全新的科学内涵,这也是地质科学发展过程中,正确处理继承与创新关系的一个光辉范例。一些学者由于对全球造山运动是否是同时性的质疑,认为建立全球统一构造年表是不可能的,也是不必要的。可是,地球作为一个整体,其动态活动应该基本上同时的,在受同一地球动力系统控制的一个大区域内,构造运动在各地虽然不是完全同时,但却大致是同时的。北美、欧洲、亚洲加里东、华力西旋回的各次构造运动基本上可以互相对比,就是证明。既然如此,我们就可以按照优先原则,将早古生代的构造旋回称为加里东旋回,将晚古生代的构造旋回称为华力西(海西)旋回。超大陆和超大陆旋回的提出,深化了构造旋回的研究,同时也为建立构造年表开辟了道路。目前已初步提出古元古代哥伦比亚、中元古代罗丁尼亚、新元古代冈瓦纳和显生宙潘吉亚等几个超大陆旋回,这样,我们便可以用超大陆旋回作为构造年表中最大一级的时间单位,每个超大陆旋回又可进一步分为几个旋回,如潘吉亚旋回可分为加里东、华力西两个旋回。我们相信,随着地质学、地球化学、地球物理学研究的深入,随着对固体地球系统和全球地质构造更加深入、全面、系统的观测研究,不久的将来我们将会像建立显生宙地层年表一样,建立起大区域以至全球的构造年表。