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The eastern Xing'an-Mongolian (Xing-Meng) Orogenic Belt (XMOB) is one of the important areas of porphyry copper (Cu)-molybdenum (Mo) deposits in China.However, studies on the exact ages of mineralization and their geodynamic significance are very limited. In this study, granodioritic rocks from the Duobaoshan Cu deposit and Daheishan Mo deposit were selected to make zircon SHRIMP U-Pb analyses in order to constrain their mineralization ages. Geochronological data indicate that two episodes of mineralization took place in the Duobaoshan Cu deposits. The granodiorite related to the Duobaoshan porphyry Cu deposit was formed in the Early Paleozoic with zircon U-Pb age of 485±8 Ma, whereas the granodiorites related to the Sankuanggou skarn-type Cu deposit were emplaced in the Jurassic with zircon U-Pb ages of 176±3 and 177±3 Ma. In the Daheishan area of Jilin Province, the emplacement age of the granodiorite porphyry related to the porphyry Mo deposit was dated at 170±3 Ma, and the unmineralized monzogranite at 178±3 Ma. Therefore, two episodes of Cu-Mo mineralization were developed in the eastern XMOB, at ~485 Ma and ~175 Ma, respectively. Based on the geological history and spatial-temporal distribution of the granitoids in northeastern (NE) China, it is proposed that the Duobaoshan Cu deposit was related to the collision of the Xing'an and Erguna blocks in the Early Paleozoic, and the Sankuanggou Cu and Daheishan Mo deposits were related to subduction of the Paleo-Pacific plate during the Jurassic.

A major advancement of Precambrian geology in the North China Craton is its tectonic subdivision into the Eastern and Western Blocks separated by the Trans-North China Orogen. However, further understanding the history of the Western Block is hindered by the lack of data for the Ordos Terrane, which is covered by basin sediments in the southern part of the Western Block. The khondalites of the Wulashan Complex are high-grade metasedimentary rocks derived from the Ordos Terrane. Therefore, U-Pb and Hf isotope studies of detrital zircons from these khondalites will provide insights into the basement nature of the Ordos Terrane. Detrital zircons from the Wulashan khondalites give U-Pb ages between 1.84 and 2.32 Ga, indicating Paleoproterozoic provenance(s) for the metasediments. These detrital zircons have concentric growth zoning, and possess ε Hf values between-8 and +9, suggesting that they crystallised from magmas derived from underlying old crust and/or juvenile materials from the mantle. The lowest ε Hf values with different ages define an evolutionary line that extrapolates to intersect the depleted mantle line at about 2.6 Ga in a ε Hf vs. time diagram. This implies that the sedimentary procenance was

Motivated by applications in computer and communication systems, we consider a processor-sharing queue where the number of jobs served is not larger than K. We propose a measure-valued fluid model for this limited processor-sharing queue and show that there exists a unique associated fluid model solution. In addition, we show that this fluid model arises as the limit of a sequence of appropriately scaled processor-sharing queues.

We study many-server queues with abandonment in which customers have general service and patience time distributions. The dynamics of the system are modeled using measurevalued processes, to keep track of the residual service and patience times of each customer.Deterministic fluid models are established to provide first-order approximation for this model.The fluid model solution, which is proved to uniquely exists, serves as the fluid limit of the many-server queue, as the number of servers becomes large. Based on the fluid model solution, first-order approximations for various performance quantities are proposed.Key words and phrases: many-server queue, abandonment, measure valued process, quality driven, efficiency driven, quality and efficiency driven.

We consider customer service chat (CSC) systems where customers can receive real time service from agents using an instant messaging (IM) application over the Internet. A unique feature of these systems is that agents can serve multiple customers simultaneously. The number of customers that an agent is serving determines the rate at which each customer assigned to that agent receives service. We consider the staffing problem in CSC systems with impatient customers where the objective is to minimize the number of agents while providing a certain service level. The service level is measured in terms of the proportion of customers who abandon the system in the long run. First we propose effective routing policies based on a static planning LP, both for the cases when the arrival rate is observable and for when the rate is unobservable. We show that these routing policies minimize the proportion of abandoning customers in the long run asymptotically for large systems. We also prove that the staffing solution obtained from a staffing LP, when used with the proposed routing policies, is asymptotically optimal. We illustrate the effectiveness of our solution procedure in systems with small to large sizes via numerical and simulation experiments.Subject classifications: call center management; queuing theory and stochastic methods. Area of review: Stochastic Models.

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