Mineralogical and geochemical alteration of low-grade metamorphic black slates due to oxidative weathering

Low-grade metamorphic black slates of Silurian and Lower Devonian ages (from the Thüringisches Schiefergebirge in Germany) were investigated to identify mineralogical and geochemical alterations that occur during the oxidative weathering black slates.The slates exhibit an intense total organic carbon decrease (>90 wt%) due to oxidative weathering. The organic matter in black slate consists mainly of non-pyrolysable material with only minor portions of pyrolysable material. In contrast to the non-pyrolysable organic matter, the concentration of pyrolysable organic matter is not decreased during weathering. Heating experiments have yielded information about a potential protection of pyrolysable organic matter against weathering, which is probably caused by a structural configuration or the intergrowth of organic matter and illite.The slates consist mainly of illite. Iron oxide (goethite) and phosphate encrustations were formed on slate surfaces as a result of oxidative and acid weathering of both iron sulfide and monazite. Kaolinite often occurs as an older encrustation beneath the iron oxide encrustations. Encrustations of iron oxide and phosphate are major sinks for trace elements, released during oxidative weathering.     

Heritage stone in South Australia

South Australia has the greatest utilisation of heritage or building stone in Australia because of its lack of timber resources. Consequently, natural stone was intensively used from the beginning of European colonisation. Building stones in South Australia, notable for their variety given the State’s diverse geology, can be challenging to designate as to their international importance. However, dimension stone in South Australia can also be designated as having national, regional, local or prospective importance. Commonly, stone in South Australia is restricted in use to a specific town, or even a single construction, and has only local significance except where use involves special stone characteristics, unusual stone masonry or use in a building with significant heritage. For instance, the town of Second Valley has a localised use of marble, likely the earliest use (1849) of this rock type in the State. Another example, ‘Adelaide Black Granite’, quarried since 1958, should probably be recognised internationally as a ‘Global Heritage Stone Resource’, as it has had intensive monumental use around Australia, utilisation as cladding in modern buildings, as well as paving and walling in Australia’s National Parliament in Canberra. It has also been exported, notably used for the Australian Embassy in Japan and for a major War Memorial at Le Hamel, France. South Australian slate quarries also provide significant heritage stone. For example, the Willunga Slate quarry south of Adelaide has been sourced for roofing slate and walling since 1840 and is arguably the longest continuous mining operation in Australia; this resource has obvious national significance given a period of quarrying extending to the present, coupled with national distribution of its products. Probably the most widespread stone sourced in South Australia is the surface limestone or calcrete, quarried in the Adelaide area until the 1850s and used for general construction. The stone continues to be used in rural areas. While arguably only of local significance, it could be considered to have national importance because of its extensive use in churches, public building, hotels, houses and simple walling across a vast area of South Australia. Additional research is needed to clarify the heritage status of many building stones used in South Australia.     

A laser ablation inductively coupled plasma mass spectrometry study of the distribution of chalcophile elements among sulfide phases in sedimentary and magmatic rocks of the Duluth Complex,Minnesota, USA

Nickel-copper sulfide deposits occur in the basal unit of the Partridge River Intrusion, Duluth Complex (Minnesota, USA). Many lines of evidence suggest that these sulfides are formed after assimilation of the proterozoic S-rich black shales, known as the Bedded Pyrrhotite Unit. In addition to S, black shales are enriched in Te, As, Bi, Sb and Sn (TABS) and the basaltic magma of the intrusion is contaminated by the partial melt of the black shales. The TABS are chalcophile and together with the platinum-group elements, Ni and Cu partitioned into the magmatic sulfide liquid that segregated from the Duluth magma. The TABS are important for the formation of platinum-group minerals (PGM) thus their role during crystallization of the base metal sulfide minerals could affect the distribution of the PGE. However, the concentrations of TABS in magmatic Ni-Cu-PGE deposits and their distribution among base metal sulfide minerals are poorly documented. In order to investigate whether the base metal sulfide minerals host TABS in magmatic Ni-Cu-PGE deposits, a petrographic and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) study has been carried out on base metal sulfide and silicate phases of the Partridge River Intrusion, Duluth Complex.Petrographic observations showed that the proportions of the base metal sulfide minerals vary with rock type. The sulfide assemblage of the least metamorphosed Bedded Pyrrhotite Unit from outside the contact metamorphic aureole consists of pyrite with minor pyrrhotite plus chalcopyrite (<5%), whereas within the contact aureole the sulfide assemblage of the Bedded Pyrrhotite Unit rocks consists dominantly of pyrrhotite (>95%) with small amount of chalcopyrite (<2%). The sulfide mineral assemblage in the xenoliths of the Bedded Pyrrhotite Unit and in the mafic rocks of the basal unit contains two additional sulfides, pentlandite and cubanite.Our LA-ICP-MS study shows that sulfides of the Bedded Pyrrhotite Unit are rich in TABS; consistent with these S-rich black shales being the source of TABS that contaminated the mafic magma. Most of the TABS are associated with sulfides and platinum-group minerals in the rocks of the Bedded Pyrrhotite Unit from the contact aureole, the Bedded Pyrrhotite Unit xenoliths and the mafic rocks of the Duluth Complex. In addition to these phases the laser maps show that silicate phases, i.e., orthopyroxene and plagioclase contain Sn and Pb respectively. In contrast, in the least metamorphosed samples of the Bedded Pyrrhotite Unit from outside the contact aureole although the pyrite contains some TABS mass balance calculations indicates that most the TABS are contained in other phases. In these rocks, galena hosts significant amounts of Te, Bi, Sb, Sn and Ag and few very small grains of Sb-rich phases were also observed. The host phases for As were not established but possibly organic compounds may have contributed.     

The Messinian event in the Paratethys: Astronomical tuning of the Black Sea Pontian

This study presents new data on the orbitally calibrated Maeotian/Pontian and Pontian record of the Black Sea Basin (Paratethys) obtained by time-series analysis of magnetic susceptibility (MS) data from relatively deep-water Upper Miocene sediments exposed in the Zheleznyi Rog section (Taman Peninsula, Russia). In the studied interval, a ∼145-m-long sedimentary sequence, spectral analysis revealed statistically significant signals with 6.1–8.2 m and 3.0–4.0 m wavelength. These signals correspond to the obliquity and precession cycles, respectively. This study correlates the main steps of Messinian Salinity Crisis (MSC) of the Mediterranean to the Black Sea Pontian record based on astronomical tuning of the study sequence and evaluation of integrated biostratigraphic, paleomagnetic and sedimentological data. Based on cyclostratigraphic results, Maeotian/Pontian beds with Actinocyclus octonarius accumulated from ∼6.3 to 6.1 Ma. Most of the Novorossian sediments correspond to the first MSC step. The TG 22 (5.79 Ma) and TG 20 (5.75 Ma) glacial events occur in the uppermost Novorossian record and are marked by extraordinary high values of MS. The Portaferian, dated at the base as ∼5.65 Ma and the top as ∼5.45 Ma, corresponds to the second MSC step. The Novorossian/Portaferian transition is marked by the hiatus of approximately 150–160 kyr, which agrees well with the concept of the intra-Pontian unconformity in the Black Sea Basin and a sea-level drop in the Mediterranean from 5.6 to 5.46 Ma. The ages for the base and the top of the Bosphorian were estimated as ∼5.45 Ma and ∼5.27 Ma, respectively. The base of the Bosphorian corresponds to the third Lago Mare episode caused by the high sea-level connection between the Mediterranean and Eastern Paratethys.     

The performance of the Black Sea Commission as a collaborative governance regime

It is often claimed that the Black Sea is one of the most degraded seas in the world. Management to rehabilitate the Black Sea requires cooperation between the coastal countries to be successful. However, regional cooperation in the Black Sea is poorly coordinated and lack concrete outcomes. This article analyses the performance of the Black Sea Commission in terms of enabling and fostering effective regional collaboration between the Black Sea coastal countries. The results indicate that the measures undertaken by the Black Sea Commission are effective in terms of enabling scientific and project based cooperation between the Black Sea countries. The cooperation around regional and national institutional reforms to tackle the Black Sea environmental problems is found to be weak. Despite the existing mechanisms and willingness of countries to cooperate, the implementation of the established strategic action plan for the environmental protection and rehabilitation of the Black Sea is limited. Most of the limitations of the Black Sea Commission's regime are found in its institutional and legal frameworks, which constrain the effectiveness of collaborative efforts of the Black Sea countries. To be fully functional, the collaborative governance regime of the Black Sea Commission has to be improved. Recommendations as to how these may be addressed to enhance the regime's capacity to ensure effective marine collaborative governance in the region are presented in this article.     

塔里木盆地阿克苏地区下寒武统玉尔吐斯组两套黑色岩系的差异及成因

玉尔吐斯组黑色页岩是塔里木盆地寒武系盐下最具有潜力的烃源岩之一,普遍认为其沉积于统一、相似的沉积环境(斜坡相),而作者的研究结果与上述结论不符。为了探讨两套在岩石矿物组合方面完全不同的黑色岩系分布规律和成因,并重建其各自的沉积模式,本文对研究区12条剖面进行了详细描述、测量,从沉积学特征、岩矿鉴定入手,结合扫描电子显微镜、X-衍射、地球化学等分析手段,着重研究了库勒剖面和于提希剖面两套黑色岩系的沉积学特征和地球化学特征差异。沉积层序、岩石矿物组合、微量元素富集系数、氧化还原敏感元素比值(V/(V+Ni)、V/Cr、U/Th)、REE+Y配分模式、有机质含量以及饱和烃色谱特征分析结果表明:两套黑色页岩均为有机质高度富集的,处于热成熟生油阶段的海相优质烃源岩(干酪根类型Ⅱ1-Ⅱ2型,第一套黑色页岩TOC均值为5.37%,第二套TOC均值为1.46%),均沉积于海水氧化-还原分层的还原环境,但各自的空间展布规律和控制因素差异较大。建立了热液喷流缺氧模式和斜坡缺氧沉积模式:第一套黑色页岩主要沉积于第一个旋回海侵高峰期水体较深、沉积速率较高的内缓坡,其发育主要受热液喷流活动、微生物活动以及氧化还原条件影响,分布范围广,台内厚,缓坡带薄,靠近台内或台地内部热液喷流中心的裂洼陷主要控制着该套黑色页岩的展布,成烃生物以底栖藻类、细菌为主,少量浮游藻类为辅;而第二套黑色页岩主要沉积于第二旋回海侵初期水体不断变深的中-外缓坡低能带,其发育主要受古生产力、氧化还原条件以及古地形(斜坡陡缓)控制,分布范围局限,外缓坡带厚度较稳定,靠近台内不发育,成烃生物以浮游藻类为主,微生物和低等水生生物为辅,其发育条件则在台缘中-外缓坡更为有利。     

Massive antigravity field and incomplete black hole evaporation

If gravity is a mixture of the ordinary attractive force carried by the massless graviton, and of a repulsive force carried by a particle with nonzero mass, an evaporating black hole might leave a stable remnant.     

Sedimentology of the debris-flow-dominated Warm Spring Canyon alluvial fan, Death Valley, California

Facies analysis of widely distributed exposures of the 32·6 km² and 8·1-km-long Warm Spring Canyon fan, central Death Valley, shows that it has been built principally by debris-flow deposits. These deposits were derived from a mature Panamint Range catchment mostly underlain by Precambrian mudrock, quartzite and dolomite. Stacked, clast-rich and matrix-supported debris-flow lobes of slightly bouldery, muddy, pebble–cobble gravel in beds 20–150 cm thick dominate the fan from apex to toe, accounting for 75–98% of most exposures. Interstratified with the debris flows are less abundant (2–25% of cuts), thinner (5–30 cm) and more discontinuous beds of clast-supported and imbricated, pebble–cobble gravel deposited by overland flows and gully flows. This facies formed by the surficial fine-fraction water winnowing of the debris flows primarily during recessional flood stage of the debris-flow events. Two other facies associations make up a small part of the fan. The incised-channel tract consists of a 250-m-wide clast-supported ribbon of irregularly to thickly bedded, boulder, pebble, cobble gravel nested within debris-flow deposits. This channel fill is oriented generally perpendicular to the Panamint range front. It formed by extensive erosion and winnowing of debris flows deposited within the incised channel, into which all water discharge from the catchment is funnelled. The limited presence of this facies only straddling the present incised channel indicates that this channel overall has maintained a consistent position on the fan except for slight lateral shifts, some caused by strike-slip offset. Fault offset temporarily closed the upper incised channel, causing recessional debris-flow mud to be ponded behind the dam. The other local facies assemblage consists of subrounded to rounded, moderately sorted pebble gravel in low-angle cross-beds that slope both basinwards and fanwards. This gravel was deposited in beachface, backshore and shoreface barrier-spit environments that developed where Lake Manly impinged on the Warm Spring fan during late Pleistocene time. These deposits straddle headcuts into, and were derived from, erosion of the debris-flow deposits. Wave energy sorted finer sediment from the shore zone, concentrated coarser sediment and rounded the coarse to very coarse pebble fraction by selective reworking.     

Methane gas Seeps Along the Oxic/Anoxic Gradient in the Black Sea: Manifestations, Biogenic Sediment Compounds and Preliminary Results on Benthic Ecology

Abstract. Sediment parameters (grain size, organic content, chloroplastic pigments, Adenylates, Potential hydrolytic activity and electron transport system activity) and benthic biota were studied in methane seep area south-west of the Crimean Peninsula in the Black Sea over a depth range from 60 to 260m. A control transect with similar depths was performed in an adjacent nonseep area. Methane seepage in this region occurs from 35 to ˜ 85m depth, passing the oxic anoxic interface zone at 130 to 180m. The methane seep areas were characterized by abundant carbonate precipitates which occurred in various shapes from small, flat structures to tall chimneys with increasing anoxia. The carbonates were associated with distinct bacterial mats. Most of the measured biochemical parameters in the sediment were quite similar in the seep and nonseep areas. The content of organic matter was higher and grain size was more uniform in the nonseep areas. However, the seep areas were charaterized by highter proportions of the larger fauna (size classes 0.5–1 mm and ≥ 1mm) as well as increased total numbers of benthic fauna in the suboxic and upper anoxic zone. The animals did not show any seep-specific adaptations. In addition to methane seepage, highly variable hydrochemical and sedimentary conditions on the lower shelf and upper slope may also play an important role in structuring the composition and distribution of the benthic fauna.