The bluestones of Stonehenge

How and why the bluestones arrived at Stonehenge, the UK's most revered ancient monument, has long held people's imagination. The key to understanding these questions relies heavily on the location of their sources. Following early studies in the late eighteenth and early nineteenth centuries, which proposed various places but in particular south‐west England, H.H. Thomas, in 1923, suggested that they came from the Mynydd Preseli, in north Pembrokeshire, Wales. Thomas proposed a number of key locations for the geographical origin of the stones. However, recent investigations have called those locations into question, identifying different sources albeit from the same broad area in north Pembrokeshire. Identification of these proposed new sites has led to archaeological excavations and important new discoveries including new suggested routes for the transport of the bluestones from the Preseli Hills to Stonehenge some 230 km away.     

Textbook of pollen analysis - once again!

Book reviewed in this article:
Faegri, K. & Iversen, J. 1989: Textbook of Pollen Analysis     

Evolution of the Central Asian Orogenic Supercollage since Late Neoproterozoic revised again

Revision of crustal architecture and evolution of the Central Asian Orogenic Supercollage (CAOS) between the breakup of Rodinia and assembly of Pangea shows that its internal pattern cannot be explained via a split of metamorphic terranes from and formation of juvenile magmatic arcs near the East European and Siberian cratons, followed by zone-parallel complex duplication and oroclinal bending of just one or two magmatic arcs/subduction zones against the rotating cratons. Also, it cannot be explained by breakup of multiple cratonic terranes and associated magmatic arcs from Gondwana and their drift across the Paleoasian Ocean towards Siberia. Instead, remnants of early Neoproterozoic oceanic lithosphere at the southern, western and northern periphery of the Siberian craton, as well as Neoproterozoic arc magmatism in terranes, now located in the middle of the CAOS, suggest oceanic spreading and subduction between Eastern Europe and Siberia even before the breakup of Rodinia at 740–720 Ma. Some Precambrian terranes in the western CAOS and Alai-Tarim-North China might have acted as a bridge between Eastern Europe and Siberia.The CAOS evolution can be rather explained by multiple regroupings of old and juvenile crust in eastern Rodinia in response to: 1) 1000–740 Ma propagation of the Taimyr-Paleoasian oceanic spreading centres between Siberian and East European cratons towards Alai-Tarim-North China; 2) 665–540 Ma opening and expansion of the Mongol-Okhotsk Ocean, collision of Siberian and East European cratons with formation of the Timanides and tectonic isolation of the Paleoasian Ocean; 3) 520–450 Ma propagation of the Dzhalair-Naiman and then Transurals-Turkestan oceanic spreading centres, possibly from the Paleotethys Ocean, between Eastern Europe and Alai-Tarim, essentially rearranging all CAOS terranes into a more or less present layout; and 4) middle to late Paleozoic expansion of the Paleotethys Ocean and collision of Alai-Tarim-North China cratons with CAOS terranes and Siberian craton to form the North Asian Paleoplate prior to its collision with Eastern Europe along the Urals to form Laurasia. Two to five subduction zones, some stable long-term and some short-living or radically reorganized in time, can be restored in the CAOS during different phases of its evolution.     

再论冻胀量与冻胀力之关系

讨论了新出版的《水工建筑物抗冰冻设计规范》（DL／T5082－1998）（98版）中的地表冻胀量对法向冻胀力影响的问题，认为地表冻胀量是冻胀率沿整个冻深的叠加，法向冻胀力则是在冻结锋面上冻胀应力沿基础影响范围之内的积分，法向冻胀力与地表冻胀量没有直接联系。     

东秦岭钼矿带成矿特征及其与美国克莱马克斯-亨德森钼矿带的对比

东秦岭钼矿带是中国最主要的钼矿带,钼矿呈近东西向展布。钼矿以斑岩型为主,从南到北,钼矿带钼矿大体有斑岩Cu-Mo矿、斑岩Mo矿、斑岩Au-Mo矿分带的趋势,与从俯冲带到克拉通边缘斑岩Cu矿、斑岩Cu-Mo矿、斑岩Mo矿依次发育的分带现象相似,表明钼矿的形成与扬子地块向华北地块俯冲有关。根据钼矿Re-Os年龄资料统计钼矿分为～220Ma、～140Ma和～110Ma三期,其成矿动力学背景分别为碰撞造山、碰撞造山后伸展和中国东部岩石圈减薄。钼矿流体包裹体均一温度介于83℃～424℃;平衡盐度介于0.61%～42.5%。流体包裹体水的δD介于-100‰～-40‰,δ18OH2O介于-4.3‰～8.7‰;且从成矿早期到晚期流体包裹体水的δD和δ18OH2O分别变小,表明钼矿的成矿流体主要来源于岩浆,后期有大气水的加入。东秦岭钼矿的铅同位素为206Pb/204Pb=17.12～17.89、207Pb/204Pb=15.23～15.70、208Pb/204Pb=37.57～39.10,与区域下地壳铅同位素一致;小斑岩体的Sri=0.705～0.714,δ18O=7.2‰～12.1‰,与I型花岗岩的锶、氧同位素相一致,表明钼矿的成矿物质主要来源于下地壳。东秦岭钼矿带的钼资源总量占中国钼资源的51%以上,美国克莱马克斯-亨德森钼矿带(Climax and Hender-son)的钼资源总量占美国钼矿资源的42%以上,美国和中国的钼资源在世界上的排名分别为第一和第二位,两钼矿带是世界钼资源高度集中的两个区域。克莱马克斯-亨德森钼矿带位于美国中西部、美洲克拉通西缘;钼矿主要形成于33～18Ma,稍晚于拉腊米(Laramide,75～54Ma)陆内造山运动;钼矿形成于碰撞造山后伸展环境。东秦岭与克莱马克斯两钼矿带相比:1)两钼矿带都位于克拉通边缘;2)两钼矿带的钼矿化都形成于陆内碰撞造山之后的伸展环境,与成矿有关的岩体都为花岗斑岩小岩体;3)两钼矿带钼矿的辉钼矿平均丰度分别为0.073%～0.140%和0.171%～0.264%,东秦岭钼矿的丰度明显较低;4)两钼矿带钼矿的辉钼矿成矿温度分别为300～400℃和460～600℃,东秦岭钼矿明显较低,反映与其成矿有关的岩浆的侵位深度较浅。通过两钼矿带间的综合对比得出:克拉通边缘经历陆内碰撞造山作用后在伸展环境下有利于斑岩钼矿的形成;与钼矿有关的小斑岩体岩浆的侵位深度影响钼矿中辉钼矿的丰度,岩浆的侵出深度越深其钼矿的辉钼矿品位越高。     

Correlation of Tectono-Stratigraphic Units in Northern Thailand with Those of Western Yunnan (China)

Ｔｈｅｃｏｒｒｅｌａｔｉｏｎｏｆｔｅｃｔｏｎｏ ｓｔｒａｔｉｇｒａｐｈｉｃｕｎｉｔｓｏｆＮｏｒｔｈｅｒｎＴｈａｉｌａｎｄｗｉｔｈｔｈｏｓｅｏｆＷｅｓｔｅｒｎＹｕｎｎａｎ (Ｃｈｉｎａ)ｉｓｓｔｉｌｌｌｉｔｔｌｅｕｎｄｅｒｓｔｏｏｄ ,ｐａｒｔｌｙｂｅｃａｕｓｅｏｆｔｈｅ ｐａｕｃｉｔｙｏｆｇｅｏｌｏｇｉｃａｌｄａｔａｆｒｏｍｔｈｅＵｎｉｏｎｏｆＭｙａｎｍａｒａｎｄｔｈｅＬａｏｓ,ａｎｄｐａｒｔｌｙｄｕｅｔｏｔｈｅｃｏｎｆｌｉｃｔｉｎｇｇｅｏｄｙｎａｍｉｃｃｏｎｃｅｐｔｓａｄｏｐｔｅｄｂｙｖａｒｉｏｕｓａ…     

Sequence Characteristics of Foreland Basin and Its Difference from Those of Other Types of Basin

Based on the case history study of sequence stratigraphic framework,sequence model,and the controlling factors on sequence formation in the southern Junggar foreland basin,a contrasting comparison of the characteristics among the foreland basin,the faulted basin,and the sag basin is made in the aspects of sequence architecture,filling style,the controlling factors on sequence development,the migrations of basin center and depocenter,etc..The current study results show that there are major differences and th...     

Oxygen Isotopic Compositions in a Plagioclase-Olivine Inclusion from Ningqiang Similar to Those in Al-rich Chondrules

We report the petrology and oxygen isotopic composition, using a Cameca NanoSIMS 50L ion microprobe, of a plagioclase–olivine inclusion, C#1, found in the Ningqiang carbonaceous chondrite. In addition to major phases (plagioclase, spinel and olivine), C#1 is also surrounded by a pyroxene rim (64 vol % Ca-rich and 36 vol % Ca-poor pyroxenes). On a three-isotope oxygen diagram, δ17O vs. δ18O, the compositions of individual minerals analyzed in C#1 fall along the carbonaceous chondrite anhydrous mineral line (CCAM), and oxygen isotopic compositions in C#1 show significant variability in δ18O and δ17O. The oxygen isotopic compositions of the pyroxene rim minerals are similar to those of the other host minerals, which suggests that the rim likely formed from the same melting process as the host. The rim is considered to have formed as a result of interaction between an 16O-poor gas and a melt. Some spinel grains are typically 16O-rich and likely of relict origin, which is similar to 16O-rich Ca-, Al-rich inclusions, which are probably a precursor of C#1. The inclusion then likely melted in an 16O-poor region where chondrules form, accompanied by oxygen isotope exchange with an 16O-poor gas. Some anorthite, pyroxene and spinel might have undergone fluid-assisted thermal metamorphism on the Ningqiang chondrite parent body. The oxygen isotope data and evolution of the C#1 plagioclase–olivine inclusion are similar with those of Al-chondrules in chondrites.     

There and back again: Epiphany, disillusionment, and rediscovery in political ecology

This paper reviews the experience of discovering, abandoning, and rediscovering elements of the work of political ecologist Piers Blaikie from the period spanning 1992-2006. In the process, we analyze the cyclic fate of critical ideas in the field of political ecology, including especially the “chain of explanation,” during a tumultuous period where materialist and constructivist theorists encountered one another. The paper concludes with a specific discussion of the power of traditional tools in political ecology for addressing current socio-ecological crises, specifically HIV/AIDS in southern Africa.     

From Kerala to Dubai and back again: Construction migrants and the global economic crisis

As a crisis that was precipitated in part by risky forms of investment in the built environment, construction workers, and particularly migrants employed in the industry have been at the forefront of job-losses worldwide since 2008. I offer a reading of construction unemployment through David Harvey’s theorisation of the secondary circuit of capital, arguing that these trends reflect the industry’s immanent connections to the built environment and to volatile, debt-fuelled urbanisation strategies which have played a crucial role in absorbing global capital surpluses in recent years. I ground this international perspective through a case study on the crisis experiences of a group of migrant construction workers from the south Indian state of Kerala who lost their jobs in Dubai in 2009. Based on interviews with migrants who returned home following the collapse of the emirate’s construction sector, I explore how a number of place-specific relationships that transect the Kerala–Dubai construction labour market served to compound these workers’ economic insecurity following the crisis. These include the immense migration debts that migrants shouldered, the insecure and exploitative character of employment in Dubai’s building trades, and the particular vulnerability of Dubai’s construction markets to the retreat of finance capital from the Gulf region in 2008. Workers’ accounts offer insights into the uneven and trans-local geometries of risk that define contemporary construction work in Dubai. More broadly, they provide a key perspective on the precarious producer geographies that underpin the secondary circuit of capital.     

Chemical, structural, and chemical-structural varieties of minerals and once again on ways to rationalize mineralogical nomenclature

The names of minerals are mostly irrational with respect to their chemical composition and crystal structure. The division of mineral species into structural and chemical-structural subspecies or varieties is proposed to simplify and rationalize mineral nomenclature. Special modifiers could be used and written after the root name of an initial mineral. For example, the eudialyte-group minerals could be divided into eudialyte-(CaMn), -(CaFe), -(MnCa), -(CaSr), and -(CaH) and alluaivite. The format of such modifiers should be a matter of discussion and approval.     

Off the Shelves—new dinosaur species from Western Canada and the importance of museum collections,again

It seems almost on a weekly basis that a new discovery in palaeontology is announced. Perhaps, in part, this is because the outlets for publishing have increased, with new online publications, or at least—once paper and bound only—the traditional sources now have internet accessibility allowing priory viewing to the print version. There is also the fact that dinosaurs and other fossils (and the ideas that surround them) are a marketable item; for authors, and the institutions that house the specimens or researchers. The fact is that in a news cycle, which is almost below hourly, and amongst the sensational stress and despair of many of the stories, fossils are a quick ‘feel‐good’ or minimally distractive piece. Collectively, palaeontologists and their fossils are more often than not taking advantage of these public opportunities.     

中亚地区与中国西部盆地类比及其油气勘探潜力

中国西部盆地和中亚某些含油气盆地在地质背景和石油地质条件等方面有一定的相似性,从盆地结构上看,中亚地区的盆地与中国西部盆地大多为具有不同构造属性的构造阶段,相互叠置的叠合盆地;从烃源岩发育特征来看,中下侏罗统的含煤岩系使中国西部与中亚地区烃源层有较好的可比性.勘探实践证明,无论在中亚还是在中国西部该含煤岩系是最重要的烃源层之一,但中国西部绝大多数盆地广泛发育古生界烃源岩,这无疑大大增强了中国西部盆地的生烃潜力.从储集岩特征来看,中亚地区含油气盆地以发育中一新生界储层为主,而中国西部大部分盆地不仅广泛分布中一新生界储层,具有发育古生界储集层的优势;从资源类型来看,中亚地区以天然气占有绝对优势,而中国西部除天然气外,石油资源也有良好的勘探前景.总的来看,中国西部的油气勘探潜力要优于中亚地区的大多数盆地.     

Stuck in a mess (again): A response to Johnston, Fairbrother, Hayes, Hoare and Jones

A response to Johnston et al.’s criticisms of my earlier paper about the Cold War and geography’s quantitative revolution that I am overly deterministic and fail to prove my case.