Cooling flows as a calorimeter of active galactic nucleus mechanical power

The assumption that radiative cooling of gas in the centres of galaxy clusters is approximately balanced by energy input from a central supermassive black hole implies that the observed X-ray luminosity of the cooling flow region sets a lower limit on active galactic nucleus (AGN) mechanical power. The conversion efficiency of the mechanical power of the AGN into gas heating is uncertain, but we argue that it can be high even in the absence of strong shocks. These arguments inevitably lead to the conclusion that the time-averaged mechanical power of AGNs in cooling flows is much higher than the bolometric luminosity of these objects observed currently.
The energy balance between cooling losses and AGN mechanical power requires some feedback mechanism. We consider a toy model in which the accretion rate on to a black hole is set by the classic Bondi formula. Application of this model to the best studied case of M87 suggests that accretion proceeds at approximately the Bondi rate down to a few gravitational radii with most of the power (at the level of a few per cent of the rest mass) being carried away by an outflow.     

Absorption of nuclear γ-rays on the starlight radiation in FR I sources: the case of Centaurus A

Several BL Lac objects are confirmed sources of variable and strongly Doppler-boosted TeV emission produced in the nuclear portions of their relativistic jets. It is more than probable that also many of the Fanaroff–Riley type I (FR I) radio galaxies, believed to be the parent population of BL Lacs, are TeV sources, for which Doppler-hidden nuclear γ-ray radiation may be only too weak to be directly observed. Here we show, however, that about 1 per cent of the total time-averaged TeV radiation produced by the active nuclei of low-power FR I radio sources is inevitably absorbed and re-processed by photon–photon annihilation on the starlight photon field, and the following emission of the created and quickly isotropized electron–positron pairs. In the case of the radio galaxy Centaurus A, we found that the discussed mechanism can give a distinctive observable feature in the form of an isotropic γ-ray halo. It results from the electron–positron pairs injected to the interstellar medium of the inner parts of the elliptical host by the absorption process, and upscattering starlight radiation via the inverse-Compton process mainly to the GeV–TeV photon energy range. Such a galactic γ-ray halo is expected to possess a characteristic spectrum peaking at ∼0.1 TeV photon energies, and the photon flux strong enough to be detected by modern Cherenkov Telescopes and, in the future, by GLAST. These findings should apply as well to the other nearby FR I sources.     

Structural and stratigraphical constraints on the kinematics history of the Southern Tan–Lu Fault Zone during the Mesozoic Anhui Province, China

The Tan–Lu Fault Zone (TLFZ) extends in a NNE–SSW direction for more than 2000 km in Eastern China. It has been considered either as a major sinistral strike-slip fault, as a suture zone or as a normal fault. We have conducted a structural analysis of the southern segment of this fault zone (STLFZ) in the Anhui Province. The ages (Triassic to Palaeocene) of the formations affected by the faults have been re-appraised taking into account recent stratigraphical studies to better constraint the ages of the successive stages of the kinematics of the STLFZ. Subsequently, the kinematics of the faults is presented in terms of strain/stress fields by inversion of the striated fault set data. Finally, the data are discussed in the light of the results obtained by previous workers.We propose the following history of the STLFZ kinematics during the Mesozoic. At the time of collision, a  NNE orientated Tan–Lu margin probably connected two margins located north of the Dabie and Sulu collision belts. During the Middle–Late Triassic, the SCB has been obliquely subducted below the NCB along this margin which has acted as a compressional transfer zone between the Dabie and Sulu continental subduction zones. The STLFZ has been initiated during the Early Jurassic and has acted as a sinistral transform fault during the Jurassic, following which the NCB/SCB collision stopped. A  NW-trending extension related to metamorphic domes was active during the basal Early Cretaceous ( 135–130 Ma); it has been followed by a NW–SE compression and a NE–SW tension during the middle–late Early Cretaceous ( 127 to  105 Ma, possibly  95 Ma); at that time the TLFZ was a sinistral transcurrent fault within the eastern part of the Asian continent. During the Late Cretaceous–Palaeocene, the STLFZ was a normal fault zone under a WNW–ESE tension.     

Lamproitic Rocks from a Continental Collision Zone: Evidence for Recycling of Subducted Tethyan Oceanic Sediments in the Mantle Beneath Southern Tibet

Major and trace element, Sr–Nd–Pb isotope and mineralchemical data are presented for newly discovered ultrapotassiclavas in the Tangra Yumco–Xuruco graben in southern Tibet.The ultrapotassic lavas are characterized by high MgO, K₂O andTiO₂, low Al₂O₃ and Na₂O contents, and also have high molarK₂O/Al₂O₃, molar (K₂O + Na₂O)/Al₂O₃ and K₂O/Na₂O ratios. Theirhigh abundances of incompatible trace elements such as largeion lithophile elements (LILE) and light rare earth elements(LREE) reach the extreme levels typical of lamproites. The lamproitesshow highly radiogenic ⁸⁷Sr/⁸⁶Sr (0· 7166–0·7363) and unradiogenic ¹⁴³Nd/¹⁴⁴Nd (0· 511796–0·511962), low ²⁰⁶Pb/²⁰⁴Pb (18· 459–18· 931),and elevated radiogenic ²⁰⁷Pb/²⁰⁴Pb (15· 6732–15·841) and ²⁰⁸Pb/²⁰⁴Pb (39· 557–40· 058) ratios.On the basis of their geochemical and isotopic systematics,the lamproites in south Tibet have a distinct magma source thatcan be differentiated from the sources of potassic lavas inthe east Lhasa and Qiangtang blocks. Their high Nb/Ta ratios(17· 10–19· 84), extremely high Th/U ratios(5· 70–13· 74) and distinctive isotope compositionsare compatible with a veined mantle source consisting of partialmelts of subducted Tethyan oceanic sediments and sub-continentallithospheric depleted mantle. Identification of the lamproitesand the delineation of their mantle source provide new evidencerelevant for models of the uplift and extension of the Tibetanplateau following the Indo-Asia collision. Metasomatism by partialmelts from isotopically evolved, old sediment subducted on theyoung Tethyan slab is an alternative explanation for PrecambrianNd and Pb model ages. In this model, differences in isotopiccomposition along-strike are attributed to differences in thetype of sediment being subducted, thus obviating the need formultiple metasomatic events over hundreds of million years.The distribution of lamproites, restricted within a north–south-trendinggraben, indicates that the initiation of east–west extensionin south Tibet started at 25 Ma. KEY WORDS: lamproites; subducted oceanic sediment; Tibetan active continental collision belt     

含交叉断层的复杂地质体3维建模算法研究

在矿井生产中,出现交叉断层的区域往往是地质构造非常复杂的地方,也是危险高发的区域.对含交叉断层的3维地质建模的算法进行了研究.其主要思想是分别建立岩层和断层的TIN模型,以断层交线作为约束条件,进行带约束三角剖分,从而建立起交叉断层模型.这将有利于矿山的工程管理,减少危险的发生,作为后续采矿生产的依据.     

地下资源开采与诱发地震：现状与进展

页岩气、地热等清洁能源正成为全球能源开发日益重要的组成部分,也是我国未来能源产量增长的主体,对保障能源资源安全、支撑双碳目标意义重大。然而随着页岩气、地热等地下工业开采活动规模的不断扩大,由此引发的地震灾害问题正日益受到人们的关注。强化工业活动与诱发地震关系研究、管控相关诱发地震灾害风险成为全球面临的重要课题和挑战。基于此,笔者等调研了工业活动诱发地震的全球典型案例,系统介绍了不同国家(美国、加拿大和韩国)工业活动诱发地震的现状及其差异,并对流体注入诱发地震的主要途径、物理机制、相关作业参数和诱发地震关系等做了全面的综述。发现诱发地震不仅与流体注入参数(体积、速率等)相关,还受控于特定的区域地质背景和断裂条件。合理管控地震灾害风险、促进相关能源的开采,应该统筹开采区地质地球物理的综合调查和开采过程的动态监测。     

油源断裂内油气运移优势通道识别方法及其应用

为了研究含油气盆地下生上储式生储盖组合中油源断裂附近油气分布规律,在油源断裂内油气运移优势通道及其影响因素研究的基础上,通过确定油源断裂凸面脊和断裂填充物油气运移分布区,二者耦合建立了一套识别油源断裂内油气运移优势通道的方法,并将该方法应用于渤海湾盆地冀中坳陷廊固凹陷大柳泉地区沙三中亚段F3油源断裂内油气运移优势通道的识别中,结果表明：F3油源断裂内可识别出5条油气运移优势通道,其中4条油气运移优势通道分布在断裂南部,1条油气运移优势通道分布在断裂北部,与目前F3油源断裂附近沙三中亚段已发现油气分布在中南部和北部相吻合,表明该方法用于识别油源断裂内油气运移优势通道是可行的。