Arc‐Type Magmatism Due to Continental‐Edge Plowing Through Ancient Subduction‐Enriched Mantle

The puzzling... (See article for full abstract)

An atmospheric source of S in Mesoarchaean structurally-controlled gold mineralisation of the Barberton Greenstone Belt

The Barberton Greenstone Belt of southern Africa hosts several Mesoarchaean gold deposits. The ores were mostly formed in greenschist facies conditions, and occur as hydrothermal alteration zones around extensional faults that truncate and post-date the main compressional structures of the greenstone belt. Ore deposition was accompanied by the intrusion of porphyries, which has led to the hypothesis that gold may have been sourced from magmas. Because the transport of Au in the hydrothermal fluids is widely believed to have involved S complexes, tracing the origin of S may place strong constraints on the origin of Au. We measured multiple S isotopes in sulfide ore from Sheba and Fairview mines of the Barberton Greenstone Belt to distinguish “deep” S sources (e.g. magmas) from “surface” S sources (i.e. rocks of the volcano-sedimentary succession that contain S processed in the atmosphere preserved as sulfide and sulfate minerals). Ion probe (SIMS) analyses of pyrite from ore zones indicate mass-independent fractionation of S isotopes (Δ33S = −0.6‰ to +1.0‰) and the distribution of the analyses in the Δ33S–δ34S space matches the distribution peak of previously published analyses of pyrite from the entire volcano-sedimentary succession. Notwithstanding that the H2O–CO2 components of the fluids may have been introduced from a deep source external to the greenstone belt rocks, the fact that S bears an atmospheric signature suggests the hypothesis that the source of Au should also be identified in the supracrustal succession of the greenstone belt. Our findings differ from conclusions of previous studies of other Archaean shear-hosted Au deposits based on mineralogical and isotopic evidence, which suggested a magmatic or mantle source for Au, and imply that there is no single model that can be applied to this type of mineralisation in the Archaean

Deep-reaching fracture zones in the crystalline basement surrounding the West Congo System and their control of mineralization in Angola and Gabon

A framework of major, deep-reaching fracture zones in western Central Africa is inferred from airborne magnetometric and surface geological observations in Central Angola and Gabon. A correlation is proposed between these observations and the continental negative Bouguer anomaly. The minimum age of the inferred tectonic framework is probably Kibaran. Considerable portions are thought to have been reactivated, and others may have only originated at later stages. Its control of major structural units and the distribution of carbonatite complexes and kimberlite occurrence and of diamond and lead-zinc deposits is discussed

New near infrared fiber delivered laser sources for surgery: physical aspects and clinical implementation

Thermal energy is commonly used for surgery to control bleeding of the surgical plane. Many sophisticated techniques are used for preventing and stopping blood loss during surgery. Electrosurgery is one of the most used and one of the most common instruments in the operating theatre. Electrical currents are generated in a high frequency, which does not interfere with nerve stimulation. Besides electrosurgery, also other devices are used to create thermal effects based on various other physical principles, such as Radio Frequent Ablation (RFA), Ultrasonic, High-intensity Focussed Ultrasound (HIFU), plasma coagulation, microwave, high pressure waterjet and electroporation. Also, laser is used as an energy device for surgical applications. Lasers are unique light sources by emitting a small parallel beam of intense monochromatic light. This enables a high intensity at a small surface area inducing high temperature by absorption of light at the surface. Surgical lasers in the near and mid infrared spectrum (1470nm and above) are of interest for soft tissue excisions due to the high energy absorption in water, thus preventing heat conduction into the depth of the tissue. However, these lasers have strong differences in laser tissue effect and should be carefully considered before using in clinical practice. Since 2005, the Thulium laser has been clinically introduced. It has the highest wavelength (2013nm) that can be delivered through optical fibers. The aim of this thesis is to evaluate the advantages and additional value of the Thulium laser compared to other existing energy devices. The infrared region is very interesting as it is a wide region (810nm-10.600nm) with many kinds of laser tissue interaction. The Thulium laser (2013nm) is a relatively new laser in this region and could safely replace the 810 and 1064nm lasers for laser assisted third ventriculostomy. It is no longer necessary to pre-carbonize the laser fibers of the 810nm and 1064nm laser as the Thulium laser has direct absorption of the light in soft tissue (water) with a reproducible effect. It has good potential for endoscopic surgery in general as the laser has the ability to deliver the laser light through low OH fibers with CO2 laserlike properties. It fits through nearly every working channel due to the small dimensions of the laser fiber. For intra oral surgery the Thulium laser has an advantage over electrosurgery, especially for tumor surgery of the tongue. The absence of muscle contractions by the use of laser compared to electrosurgery has several potential benefits such as better overview of the operating field and less bleeding due to minimal tissue manipulation. The small vasculature can be easily cut and coagulated by the Thulium laser. The novel handpiece which has been developed with integrated smoke evacuation can also contribute to optimal Thulium laser usage in oral surgery. To conclude, there are more clinical applications in which the Thulium laser could be used for. There is a bright future for the Thulium laser for various applications when more surgeons become aware and appreciate the special characteristics/features of this laser

The Jiaodong gold district, northeastern China, in the context of the Late Paleozoic and Late Mesozoic large igneous provinces, orogeny and metallogeny in Eurasia

The Permo-Triassic continental large igneous provinces (LIPs) of Eurasia linked in to orogenic systems in decay. Their bulk appearance varies from the massive flood-basalts and (ultra)mafic intrusives to the groups of coeval, widely spread, diverse intrusions and extrusions of the Scattered Igneous Provinces (SIPs). In the interval from the demise of the orogens to the inception of the LIPs and SIPs, diverse ore deposits were formed which, depending on the predominant expression of the hosting system, have been interpreted as orogen-related and LIP- or SIPrelated. In the case of the voluminous (ultra)mafic complexes, amantle origin is indicated. This leads to the concept of active mantle plumes issuing from the core–mantle boundary in view of the exceptional volumes and the high temperature inferred to melt the source complexes. However, the substantial volumes of fluids that entered the sub-continental mantle on prior subduction of oceanic lithosphere lowered the solidus temperature and modified the composition of the sub-continental mantle. As a consequence, the conditional high temperature is superfluous. In this context, the setting of the Jiaodong Province and the evolution of the hosting North China Craton suggest that: 1 the introduction of fluids during prolonged subduction of oceanic lithosphere can also modify the rheology of the deep lithosphere; this reinforces the role of plate tectonic processes in the generation and the in-and extrusion of voluminous, mantle-derived melts; 2 the prolific gold deposits could form because of the stalled, subducted Pacific lithosphere slab with its oxidizing potential and its position within the mantle transition zone; as elsewhere, continentscale, translithospheric strike-slip deformation played an indispensable role in decompression and in the migration of melts, fluids, volatiles and metals; 3 orogenic gold deposits can form independent of orogenesis; should, after all, a relevant orogen be delineated in the coastal belt of eastern Asia, the question arises concerning the dependence of orogenic gold deposits on the nature of an orogen

Deep-reaching fracture zones in the crystalline basement surrounding the West Congo System and their control of mineralization in Angola and Gabon

A framework of major, deep-reaching fracture zones in western Central Africa is inferred from airborne magnetometric and surface geological observations in Central Angola and Gabon. A correlation is proposed between these observations and the continental negative Bouguer anomaly. The minimum age of the inferred tectonic framework is probably Kibaran. Considerable portions are thought to have been reactivated, and others may have only originated at later stages. Its control of major structural units and the distribution of carbonatite complexes and kimberlite occurrence and of diamond and lead-zinc deposits is discussed

The Central European, Tarim and Siberian Large Igneous Provinces, Late Palaeozoic orogeny and coeval metallogeny

The formation of the Central European and Tarim Large Igneous Provinces (LIPs) in the Early Permian coincided with the demise of the Variscan and the Southern Tianshan orogens, respectively. The Early Triassic Siberian LIP was formed in the wake of the Western Altaid orogeny in the Late Permian. These processes coincided with the development of the majority of known Late Palaeozoic and Early Mesozoic hydrothermal and magmatic ore deposits in the corresponding orogenic domains. Nickel-copper (-PGE) deposits followed directly from the evolution of the (ultra-)mafic melts which make up the LIPs. In Western Siberia, the diverse assemblage of associated noble and base metals in the Noril?sk-Talnakh Ni-Cu (-PGE) deposits suggests these metals also had their source in the mantle domain from which the (ultra-)mafic melts were generated. The same metals variably found their way into the hydrothermal ore deposits in the defunct Variscan and Southern Tianshan orogenic domains. These ore deposits have traditionally been viewed as a result of orogenic processes. However, their ages, together with the timing and nature of their by then intracontinental tectonic control cause uncertainty concerning the role of the orogens. In view of their mantle sources in their association with the Siberian LIP, the mantle contribution to these Late Palaeozoic hydrothermal ore deposits in the orogenic belts may have been more significant than previously thought. An orogenic contribution to melting of mantle complexes and to mineralisation may have resided in the earlier modification of subcontinental mantle domains by subduction of oceanic lithosphere. In all three cases, the controlling tectonic setting of orogenic cessation, LIP formation and mineralisation was dominated by translithospheric strikeslip deformation, possibly in combination with orogenic collapse and lithosphere delamination. In view of their recurrence, the orogen-lip sequences were probably not fortuitous. The controlling strike-slip faults were principal elements of the lithosphere-scale dynamic framework that led to the amalgamation of Pangaea. At this scale, the exceptionally large volume of the Siberian LIP may, in addition to the strike-slip dissection of the lithosphere, have been related to extension in the continental lithosphere of the margin of the Supercontinent (cf. Gutiérrez-Alonso et al. 2008). The peripheral extension was associated with compression in its centre. The explanation of these Large Igneous Provinces does not require the concept of an active mantle plume because deep-reaching strike-slip deformation, orogenic collapse and lithosphere delamination involved in the destruction of the orogenic edifices can have caused decompression melting in large domains of the subcontinental mantle

Busting at the seams?

In Permo-Triassic Eurasia two transcontinental mantle events can be recognized: • the c. 295-280 Ma Tarim event, between western Europe and eastern Kazakhstan (c. 8,500 km apart) and • the c. 250-245 Ma Siberia event, between western Europe and northeastern Asia (c. 10,000 km apart). Were these events driven by deep mantle plumes, shallow mantle processes, or both, or something else

New near infrared fiber delivered laser sources for surgery: physical aspects and clinical implementation

Thermal energy is commonly used for surgery to control bleeding of the surgical plane. Many sophisticated techniques are used for preventing and stopping blood loss during surgery. Electrosurgery is one of the most used and one of the most common instruments in the operating theatre. Electrical currents are generated in a high frequency, which does not interfere with nerve stimulation. Besides electrosurgery, also other devices are used to create thermal effects based on various other physical principles, such as Radio Frequent Ablation (RFA), Ultrasonic, High-intensity Focussed Ultrasound (HIFU), plasma coagulation, microwave, high pressure waterjet and electroporation. Also, laser is used as an energy device for surgical applications. Lasers are unique light sources by emitting a small parallel beam of intense monochromatic light. This enables a high intensity at a small surface area inducing high temperature by absorption of light at the surface. Surgical lasers in the near and mid infrared spectrum (1470nm and above) are of interest for soft tissue excisions due to the high energy absorption in water, thus preventing heat conduction into the depth of the tissue. However, these lasers have strong differences in laser tissue effect and should be carefully considered before using in clinical practice. Since 2005, the Thulium laser has been clinically introduced. It has the highest wavelength (2013nm) that can be delivered through optical fibers. The aim of this thesis is to evaluate the advantages and additional value of the Thulium laser compared to other existing energy devices. The infrared region is very interesting as it is a wide region (810nm-10.600nm) with many kinds of laser tissue interaction. The Thulium laser (2013nm) is a relatively new laser in this region and could safely replace the 810 and 1064nm lasers for laser assisted third ventriculostomy. It is no longer necessary to pre-carbonize the laser fibers of the 810nm and 1064nm laser as the Thulium laser has direct absorption of the light in soft tissue (water) with a reproducible effect. It has good potential for endoscopic surgery in general as the laser has the ability to deliver the laser light through low OH fibers with CO2 laserlike properties. It fits through nearly every working channel due to the small dimensions of the laser fiber. For intra oral surgery the Thulium laser has an advantage over electrosurgery, especially for tumor surgery of the tongue. The absence of muscle contractions by the use of laser compared to electrosurgery has several potential benefits such as better overview of the operating field and less bleeding due to minimal tissue manipulation. The small vasculature can be easily cut and coagulated by the Thulium laser. The novel handpiece which has been developed with integrated smoke evacuation can also contribute to optimal Thulium laser usage in oral surgery. To conclude, there are more clinical applications in which the Thulium laser could be used for. There is a bright future for the Thulium laser for various applications when more surgeons become aware and appreciate the special characteristics/features of this laser