Origin of dolomite in the Middle Ordovician peritidal platform carbonates in the northern Ordos Basin, western China

The carbonates in the Middle Ordovician Ma_5～5submember of the Majiagou Formation in the northern Ordos Basin are partially to completely dolomitized.Two types of replacive dolomite are distinguished：（1） type 1dolomite,which is primarily characterized by microcrystalline（〈30 urn）,euhedral to subhedral dolomite crystals,and is generally laminated and associated with gypsumbearing microcrystalline dolomite,and（2） type 2 dolomite,which is composed primarily of finely crystalline（30-100 urn）,regular crystal plane,euhedral to subhedral dolomite.The type 2 dolomite crystals are truncated by stylolites,indicating that the type 2 dolomite most likely predated or developed simultaneously with the formation of the stylolites.Stratigraphic,petrographic,and geochemical data indicate that the type 1 dolomite formed from near-surface,low-temperature,and slightly evaporated seawater and that the dolomitizing fluids may have been driven by density differences and elevation-related hydraulic head.The absence of massive depositional evaporites in the dolomitized intervals indicates that dolomitization was driven by the reflux of slightly evaporated seawater.The δ～（18）O values（-7.5 to-6.1 ‰） of type1 dolomite are slightly lower than those of seawaterderived dolomite,suggesting that the dolomite may be related to the recrystallization of dolomite at higher temperatures during burial.The type 2 dolomite has lowerδ～（18）O values（-8.5 to-6.7 ‰） and Sr～（2＋） concentration and slightly higher Na～＋,Fe～（2＋）,and Mn～（2＋） concentrations and～（87）Sr/～（86）Sr ratios（0.709188-0.709485） than type 1 dolomite,suggesting that the type 2 dolomite precipitated from modified seawater and dolomitic fluids in pore water and that it developed at slightly higher temperatures as a result of shallow burial.

Application of endovascular pure electrocoagulation in the management of coronary artery perforation during percutaneous coronary intervention

Coronary artery perforation(CAP)during percutaneous coronary intervention(PCI)is a serious complication associated with significant morbidity and mortality.Its incidence in the general PCI population has been reported to range from 0.50%to 0.58%.Meanwhile,in chronic total occlusion(CTO)PCI procedure,the incidence increased to 1.4%−4.4%.[1]Currently,most of CAPs are distally located and related to guidewire,especially hydrophilic guidewire manipulations.[2]To avoid urgent or emergency cardiac surgery,some commonly used techniques include balloon inflations,covered stents,and coil embolization stand as representative options in the treatment of CAP.[3]Despite the availability of treatment approaches,there is still a lack of a standard consensus about the optimal management of this challenging complication.Endovascular pure electrocoagulation is a new approach that has been reported in the management of small vessel hemorrhage disease in cerebrovascular intervention,it can also provide promising results in CAP management.