The Yao'an Pb–Ag deposit, located in the Chuxiong Basin, western Yangtze Block, is an important component of the Jinshajiang–Ailaoshan alkaline porphyry–related polymetallic intrusive belt. This complex suite o...The Yao'an Pb–Ag deposit, located in the Chuxiong Basin, western Yangtze Block, is an important component of the Jinshajiang–Ailaoshan alkaline porphyry–related polymetallic intrusive belt. This complex suite of rock bodies includes a vein of pseudoleucite porphyry within deposits of syenite porphyry and trachyte.The pseudoleucite is characterized by a variable greyish,greyish-white, and greyish-green porphyritic texture. Phenocrysts are mainly pseudoleucite with small amounts of alkali feldspar and biotite. In an intense event, leucite phenocrysts altered to orthoclase, kaolinite, and quartz.Both the pseudoleucite porphyry and the syenite porphyry samples were typical alkali-rich, K-rich, al-rich rocks with high LaN/YbNratios; enriched in light rare earth elements and large-ion lithophile elements, and depleted in high field strength elements; and with strongly negative Ta, Nb, and Ti(TNT) anomalies and slightly negative Eu anomalies—all characteristics of subduction-zone mantle-derived rock.We obtained a LA-ICP-MS zircon U–Pb age of 34.1 ± 0.3 Ma(MSWD = 2.4), which is younger than the established age of the Indian and Eurasian Plate collision.The magma derived from a Type-II enriched mantle formed in a post-collisional plate tectonic setting. The geochemical characteristics of the Yao'an pseudoleucite porphyry are powerful evidence that the porphyry'sdevelopment was closely linked to the Jinshajiang–Ailaoshan fault and to the Indian-Eurasian collision.展开更多
Contact detection between interacting blocks is of great importance to discontinuity-based numerical methods, such as DDA, DEM, and NMM. A rigorous contact theory is a prerequisite to describing the interactions of mu...Contact detection between interacting blocks is of great importance to discontinuity-based numerical methods, such as DDA, DEM, and NMM. A rigorous contact theory is a prerequisite to describing the interactions of multiple blocks. Currently, the penalty method, in which mathematical springs with high stiffness values are employed, is always used to calculate the contact forces. High stiffness values may cause numerical oscillations and limit the time step. Furthermore, their values are difficult to identify. The intention of this study is to present a two-scale contact model for the calculation of forces between colliding blocks. In this new model, a calculation step taken from the moment of contact will be divided into two time stages: the free motion time stage and the contact time stage. Actually, these two time stages correspond to two real physical processes. Based on this, we present a new numerical model that is intended to be more precise and useful in calculating the contact forces without mathematical springs. The propagation of the elastic wave during collision is of a characteristic length, which determines the volume of material involved in the contact force calculation. In conventional contact models, this range is always regarded as the length of one element, which may lead to an inaccurate calculation of contact forces. In fact, the real scale of this range is smaller than the length of a single element, and subdivided elements, which are refined according to the characteristic length and are presented in the new contact model.展开更多
In this paper, we experimentally and theoretically study the resistance force that develops when a cylinder with a flat face colliding against dry quartzite sand. Observations from experimental data clearly show that ...In this paper, we experimentally and theoretically study the resistance force that develops when a cylinder with a flat face colliding against dry quartzite sand. Observations from experimental data clearly show that the acceleration curves are characterized by a double-peak structure. The first agitated peak can be attributed to a shock process where sand responds elastically, and the valley bottom in the double-peak structure is related to a limited plastic load when a fully plastic region is formed in the sand, while the second agitated peak corresponds to a the occurrence of the maximum of viscous force in a homogeneous developed bulk flow. We use slip line theory (SL) developed in plastic mechanics to capture the value at the valley bottom, adopt the double shearing theory (DS), together with a Local Rheological Constitutive Law (LRCL) suggested in this paper, to capture the drag force generated in a homogeneous bulk flow. Good agreements in the comparisons between numerical and experimental results support the characteristic resistance by the cylinder to predict granular states.展开更多
基金funded by National Natural Science Foundation of China (Grant Number:41102049)Mineral Resources Prediction and Evaluation Engineering Laboratory of Yunnan Provincethe Program of Provincial and University Innovation Team
文摘The Yao'an Pb–Ag deposit, located in the Chuxiong Basin, western Yangtze Block, is an important component of the Jinshajiang–Ailaoshan alkaline porphyry–related polymetallic intrusive belt. This complex suite of rock bodies includes a vein of pseudoleucite porphyry within deposits of syenite porphyry and trachyte.The pseudoleucite is characterized by a variable greyish,greyish-white, and greyish-green porphyritic texture. Phenocrysts are mainly pseudoleucite with small amounts of alkali feldspar and biotite. In an intense event, leucite phenocrysts altered to orthoclase, kaolinite, and quartz.Both the pseudoleucite porphyry and the syenite porphyry samples were typical alkali-rich, K-rich, al-rich rocks with high LaN/YbNratios; enriched in light rare earth elements and large-ion lithophile elements, and depleted in high field strength elements; and with strongly negative Ta, Nb, and Ti(TNT) anomalies and slightly negative Eu anomalies—all characteristics of subduction-zone mantle-derived rock.We obtained a LA-ICP-MS zircon U–Pb age of 34.1 ± 0.3 Ma(MSWD = 2.4), which is younger than the established age of the Indian and Eurasian Plate collision.The magma derived from a Type-II enriched mantle formed in a post-collisional plate tectonic setting. The geochemical characteristics of the Yao'an pseudoleucite porphyry are powerful evidence that the porphyry'sdevelopment was closely linked to the Jinshajiang–Ailaoshan fault and to the Indian-Eurasian collision.
基金supported by the National Basic Research Program of China("973"Project)(Grant No.2015CB250903)the CAS Strategic Priority Research Program(B)(Grant No.XDB10030303)+1 种基金the National Key Technology Research and Development Program of the Ministry of Science and Technology of China(Grant No.2012BAK10B01)the Youth Science Fund of the National Natural Science Foundation of China(Grant No.11302230)
文摘Contact detection between interacting blocks is of great importance to discontinuity-based numerical methods, such as DDA, DEM, and NMM. A rigorous contact theory is a prerequisite to describing the interactions of multiple blocks. Currently, the penalty method, in which mathematical springs with high stiffness values are employed, is always used to calculate the contact forces. High stiffness values may cause numerical oscillations and limit the time step. Furthermore, their values are difficult to identify. The intention of this study is to present a two-scale contact model for the calculation of forces between colliding blocks. In this new model, a calculation step taken from the moment of contact will be divided into two time stages: the free motion time stage and the contact time stage. Actually, these two time stages correspond to two real physical processes. Based on this, we present a new numerical model that is intended to be more precise and useful in calculating the contact forces without mathematical springs. The propagation of the elastic wave during collision is of a characteristic length, which determines the volume of material involved in the contact force calculation. In conventional contact models, this range is always regarded as the length of one element, which may lead to an inaccurate calculation of contact forces. In fact, the real scale of this range is smaller than the length of a single element, and subdivided elements, which are refined according to the characteristic length and are presented in the new contact model.
基金the National Natural Science Foundation ofChina (Grant No. 11132001)
文摘In this paper, we experimentally and theoretically study the resistance force that develops when a cylinder with a flat face colliding against dry quartzite sand. Observations from experimental data clearly show that the acceleration curves are characterized by a double-peak structure. The first agitated peak can be attributed to a shock process where sand responds elastically, and the valley bottom in the double-peak structure is related to a limited plastic load when a fully plastic region is formed in the sand, while the second agitated peak corresponds to a the occurrence of the maximum of viscous force in a homogeneous developed bulk flow. We use slip line theory (SL) developed in plastic mechanics to capture the value at the valley bottom, adopt the double shearing theory (DS), together with a Local Rheological Constitutive Law (LRCL) suggested in this paper, to capture the drag force generated in a homogeneous bulk flow. Good agreements in the comparisons between numerical and experimental results support the characteristic resistance by the cylinder to predict granular states.