MESOZOIC Mo MINERALIZATION IN NORTHEASTERN CHINA DID NOT REQUIRE REGIONAL-SCALE PRE-ENRICHMENT

Northeastern China is one of the richest Mo-mineralized regions in China, with 95 Mesozoic Mo-bearing deposits and a total metal resource of >12.2 Mt Mo. The reasons behind the large-scale Mesozoic Mo mineralization in NE China remain unclear, and whether or not there was any regional-scale pre-enrichment of the source region (e.g., a Mo-rich lower crust) is still a matter of debate. In this study, whole-rock Nd and zircon Hf isotope compositions of the intrusions related to the Mo mineralization have been compiled. The results show that the isotopic compositions are highly heterogeneous among these deposits with different ages and Mo tonnages, indicating that Mo-related magmas could be derived from either ancient lower crust or relatively juvenile lower crust or via mixing of mantle-derived magmas with varying proportions of crustal melts. This suggests that different magmas, independently from their sources, can produce Mo mineralization in NE China, and, therefore, that there was probably not an unusually Mo rich basement underlying NE China. In addition, Monte Carlo simulations have been carried out to explore the magmatic processes potentially associated with the formation of magmatic-hydrothermal (porphyry- or skarn-type) Mo deposits. The results reveal that a variably large magma volume (e.g., >150 km3) was required to provide enough Mo metal to form the large (>0.1 Mt Mo) deposits. In NE China, the Jurassic Mo deposits are much more abundant and larger than the Triassic and Cretaceous deposits, which could be attributed to the specific Jurassic tectonic regime. In the Jurassic, the subduction of the Paleo-Pacific oceanic plate led to regional compression, which favors accumulation of larger amounts of magmas at depth, ultimately resulting in larger Mo deposit formation. In this study, we highlight the importance of magma volume, rather than magma source, in the formation of the Mesozoic Mo deposits in NE China.

A case of congenital ureteral atresia causing rare upper and lower urinary tract manifestations in a puppy: a case report

Background Ureteral atresia is the congenital absence of a ureteral opening, resulting in a blind-ended ureter that fails to terminate at the urinary bladder. Consequently, severe hydroureter and hydronephrosis occur ipsilateral to the atresic ureter. However, hydronephrosis contralateral to severe hydroureter, although reported in humans, is not documented in the dog. Additionally, ureteral atresia has not been reported as a cause for lower urinary tract signs directly related to extramural urinary bladder compression. This report aims to describe these unique manifestations of this congenital urinary tract disease, as well as follow-up findings after successful treatment. Case presentation A 4-month-old male Husky puppy was evaluated for pollakiuria, stranguria, and urine dribbling of 1-month duration. During the physical examination, a mass was palpated in the mid-abdomen. Diagnostic imaging and cystoscopy findings were diagnostic for right-sided ureteral atresia with secondary hydroureter and hydronephrosis. The severe right hydroureter caused lower urinary tract signs and contralateral hydronephrosis secondary to regional compression of the left distal ureter and urinary bladder. A right-sided ureteronephrectomy was performed, resolving the stranguria and pollakiuria. Significant reduction in the contralateral (left) hydronephrosis also occurred. Clinical Relevance Ureteral atresia should be considered as a differential diagnosis for lower urinary tract signs and/or bilateral hydronephrosis in a young dog. Reporting this case expands our knowledge of congenital lower urinary tract disease and the etiology of their manifestations in dogs. Surgical resolution of the congenital ureteral abnormality can result in preservation of renal function in the contralaterally obstructed kidney.

Shear-Hosted Uranium Deposits: A Review

A group of uranium deposits is described that is hosted within polyphase shear zones. The group is economically significant, collectively containing over 500,000 tonnes of uranium and several examples have been or are being mined. Over a hundred individual deposits are known widely spread over many countries. It is proposed that this group be assigned to a new shear-hosted uranium deposit category. Uranium deposition was superimposed upon intense and extensive feldspathic alteration formed during ductile deformation. This intense alteration has led to the alternative albitite-type or metasomatite-type nomenclature. The evidence is clear that in most cases uranium mineralization postdates regionally extensive feldspar alteration and is associated with a range of alteration assemblages which overprint early albite or K-feldspar dominant alteration. Abundance of hydrothermal zirconium and phosphate minerals is a common characteristic of this group which implies high activity of F and P during mineralisation, but the source of hydrothermal fluids remains uncertain. Also uncertain is the geodynamic setting of uranium mineralisation which is a consequence of absolute mineralisation age being poorly defined. Data from three of the four major districts are suggestive that mineralisation was a consequence of fluid migration along shears during regional compression. This paper reviews key aspects of the group in a mineral systems context, focussing on the four major districts of Kropyvnytskyi (Ukraine), Lagoa Real (Brazil), Mount Isa (Australia) and the Central Mineral Belt (Canada).

The recognition of transient compressional fault slow−slip along the northern shore of Hornsund Fjord, Sw Spitsbergen, Svalbard

This paper presents the results of direct 3−D fault displacement monitoring along the northern shore of Hornsund Fjord, SW Spitsbergen, Svalbard. The fault displacements have been recorded using three permanently installed optical−mechanical crack gauges since 2009. The monitoring data from all three sites provided evidence for a remarkable slip event that lasted from September 2011 to May 2012. The cause is discussed in some detail with consideration given to both exogenic (temperature changes, surface processes) and endogenic processes (isostatic rebound and regional seismicity). It is proposed that transient fault slips recorded had a tectonic origin and were caused by approximately W−E oriented compression corresponding to regional compression in the Svalbard area.

Reorientation of structures near granitic plutons and orthogonal lineaments, Russell Lake supracrustal domain, southwestern Slave Province

A complex array of folds and cleavages in metasedimentary and metavolcanic rocks in the Russell Lake domain could reflect regional compression recurrently reoriented across crustal lineaments. Several generations of steeply inclined folds trending northward across the domain curve into or interfere with folds parallel to margins of bordering granite batholiths aligned orthogonally northwest (LNW) and northeast (LNE). Sets of later subvertical cleavages strike northward, northwest parallel and oblique to LNW, and northeastward subparallel to LNE. The cleavages extend beyond the aligned margins, indicating that the association with the granites is indirect.The arrangements of folds and cleavages are consistent with intermittent redirection of subhorizontal compression of cover rocks perpendicular to orthogonal, steep crustal fractures that were intruded by syndeformational granitic plutons. Additionally, overturning of folds near plutons suggests local reorientation of compression near shallow-dipping margins. Following folding, further reorientations resulted in reversals in strike-slip bedding shear and cleavage sets locally symmetric about fold limbs.