The magmatic to hydrothermal evolution of the intrusive Mont Saint-Hilaire Complex: Insights into the late-stage evolution of peralkaline rocks

The Cretaceous Mont Saint-Hilaire complex (Quebec, Canada) comprises three major rock units that were emplaced in the following sequence: (I) gabbros; (II) diorites; (III) diverse partly agpaitic foid syenites. The major element compositions of the rock-forming minerals, age-corrected Nd and oxygen isotope data for mineral separates and trace element data of Fe-Mg silicates from the various lithologies imply a common source for all units. The distribution of the rare earth elements in clinopyroxene from the gabbros indicates an ocean island basalt type composition for the parental magma. Gabbros record temperatures of 1200 to 800 degrees C, variable silica activities between 0 center dot 7 and 0 center dot 3, and f(O2) values between -0 center dot 5 and +0 center dot 7 (log delta FMQ, where FMQ is fayalite-magnetite-quartz). The diorites crystallized under uniform a(SiO2) (a(SiO2) = 0 center dot 4-0 center dot 5) and more reduced f(O2) conditions (log delta FMQ similar to-1) between similar to 1100 and similar to 800 degrees C. Phase equilibria in various foid syenites indicate that silica activities decrease from 0 center dot 6-0 center dot 3 at similar to 1000 degrees C to < 0 center dot 3 at similar to 550 degrees C. Release of an aqueous fluid during the transition to the hydrothermal stage caused a(SiO2) to drop to very low values, which results from reduced SiO(2) solubilities in aqueous fluids compared with silicate melts. During the hydrothermal stage, high water activities stabilized zeolite-group minerals. Fluid inclusions record a complex post-magmatic history, which includes trapping of an aqueous fluid that unmixed from the restitic foid syenitic magma. Cogenetic aqueous and carbonic fluid inclusions reflect heterogeneous trapping of coexisting immiscible external fluids in the latest evolutionary stage. The O and C isotope characteristics of fluid-inclusion hosted CO(2) and late-stage carbonates imply that the surrounding limestones were the source of the external fluids. The mineral-rich syenitic rocks at Mont Saint-Hilaire evolved as follows: first, alkalis, high field strength and large ion lithophile elements were pre-enriched in the (late) magmatic and subsequent hydrothermal stages; second, percolation of external fluids in equilibrium with the carbonate host-rocks and mixing processes with internal fluids as well as fluid-rock interaction governed dissolution of pre-existing minerals, element transport and precipitation of mineral assemblages determined by locally variable parameters. It is this hydrothermal interplay between internal and external fluids that is responsible for the mineral wealth found at Mont Saint-Hilaire

Prevalence of bisphosphonate associated osteonecrosis of the jaws in multiple myeloma patients

<p>Abstract</p> <p>Background</p> <p>Bisphosphonate-associated osteonecrosis of the jaws (BP-ONJ) is an adverse effect of bisphosphonate treatment with varying reported incidence rates.</p> <p>Methods</p> <p>In two neighboring German cities, prevalence and additional factors of the development of BP-ONJ in multiple myeloma patients with bisphosphonates therapy were recorded using a retrospective (RS) and cross-sectional study (CSS) design. For the RS, all patients treated from Jan. 2000 - Feb. 2006 were contacted by letter. In the CSS, all patients treated from Oct. 2006 - Mar. 2008 had a physical and dental examination. Additionally, a literature review was conducted to evaluate all articles reporting on BP-ONJ prevalence. PubMed search terms were: bisphosphonat, diphosphonate, osteonecrosis, prevalence and incidence.</p> <p>Results</p> <p>In the RS, data from 81 of 161 patients could be obtained; four patients (4.9%) developed BP-ONJ. In the CSS, 16 of 78 patients (20.5%) developed BP-ONJ. All patients with BP-ONJ had received zoledronate; 12 of these had had additional bisphosphonates. All except one had an additional trigger factor (tooth extraction [n = 14], dental surgical procedure [n = 2], sharp mylohyoid ridge [n = 3]).</p> <p>Conclusion</p> <p>The prevalence of BP-ONJ may have been underestimated to date. The oral examination of all patients in this CSS might explain the higher prevalence, since even early asymptomatic stages of BP-ONJ and previously unnoticed symptomatic BP-ONJ were recorded. Since nearly all patients with BP-ONJ had an additional trigger factor, oral hygiene and dental care might help to reduce BP-ONJ incidence.</p