Post-Meeting Field Trip 1

Introduction 

Ultrahigh-pressure metamorphism in the Dabie orogen: Tracing the continental crust into the mantle 

Time Duration: 25-27, October,2024 

Leader: Prof. WANG Qin, Nanjing University 

Major cities or towns on the line: Beijing City (start), Hefei City, Nanjing City (end) 

Geological features for observation and investigation:

 The Dabie-Sulu orogen is one of the largest (~30,000 km2) and best exposed ultrahigh-pressure (UHP) metamorphic terranes in the world. It was formed by northward subduction of the Yangtze craton beneath the North China craton in the Triassic. The central Dabie UHP metamorphic belt consists of interlayered pelitic and granitic gneisses, phengite-quartz schist, quartzite, marble, eclogite and garnet peridotite. These rocks commonly contain coesite and occasionally microdiamond as inclusions, and was subjected to the peak metamorphism under P-T conditions of 3.0-4.0 GPa and 700-850 ºC (i.e., >120 km) at 234-240 Ma. After a rapid syn-convergence exhumation under eclogite facies, these rocks experienced slow exhumation under amphibolite to greenschist facies conditions from the Latest Triassic to the Jurassic. In the Early Cretaceous, large amounts of granitic rocks intruded into the Dabie Mountains and resulted in a domal structure and the final unroofing of the UHP rocks. 

During this field trip, we will visit four classic outcrops to see different types of eclogites and their country rocks: the Bixiling eclogite-garnet peridotite complex, the Xindian microdiamond-bearing eclogites within marbles, the Yezhai folded eclogites and eclogite-facies breccia, and a kilometer-scale eclogitic sheath fold in Shuanghe. These UHP metamorphic rocks provide a window to trace deep subduction and exhumation processes of continental supracrustal materials during continental collision.

Field Trip Price 

3000 CNY  per-person (2400 CNY if share a standard room with two beds), which covers：

• High-speed train ticket from Beijing to Hefei (first class);

• Hotel stay (2 nights in Qianshan County on Oct. 25-26, one night in Nanjing University on Oct. 27), four-star hotel, meals and water in the field;

• Field vehicle rental/gasoline/toll, travel insurance;

• Administrative fees for preparing and setting up the field trip;

• Fees for entering private properties during the field excursion without sightseeing, etc.

Schedule 

The three-day field trip in the Dabie orogen will be guided by Prof. Qin Wang from Nanjing University. The schedule is as follows:

Day 1, Oct. 25 (Friday) 

• 6:00-6:50: Have breakfast and check out;

• 7:00: Departure from the Beijing New Century Hotel to the Beijing South Station;

• 8:47-13:31: Beijing to Hefei South Station, Train No. G321, high-speed train, first class, have lunch in the strain;

• 13:31-14:00: Take minibus in the parking area of the Hefei South Station (Qin will book two buses from Nanjing to Hefei, with 2-3 her graduate students as field assistants);

• 14:00-16:00: Hefei South Station to Yezhai Village, 181 km, 2 hours;

• 16:00-17:30: Stop 1: Yezhai folded eclogites and veins (introduction about the Dabie UHP belt, one-hour observation and sampling);

• 17:30-17:45: Seventh Fairy International Hotel, Qianshan County;

• 18:30: Dinner.

Day 2, Oct. 26 (Saturday) 

• 7:00-8:00: Have breakfast, departure at 8:00;

• 8:00-8:30: Seventh Fairy International Hotel to Gaofeng Village, 25 km;

• 8:30-9:30：Stop 2: The Xindian microdiamond-bearing eclogites in marbles (60 minutes observation, this valuable site cannot take samples);

• 9:30-10:15：Xindian to Bixiling (25.8 km, ~40 minutes driving);

• 10:15-11:15: Stop 3: The Bixiling eclogite-garnet peridotite complex (one-hour observation and sampling);

• 11:15-12:10：Return to Seventh Fairy International Hotel (35.6 km, ~50 minutes driving);

• 12:30-13:30：Lunch;

• 14:00-14:40: Seventh Fairy International Hotel to Shuanghe (Hanchangchong Village) (25.3 km, 40 minutes driving);

• 14:40-17:00: Stop 4: The Shuanghe UHP eclogites and country rocks (20 minutes introduction and take a group picture, two hours walking, observation and sampling);

• 17:00-17:40: Return to Seventh Fairy International Hotel;

• 18:00 Dinner.

Day 3, Oct. 27 (Sunday) 

• 7:00-8:00: Have breakfast and check out;

• 8:00-9:00: From Seventh Fairy International Hotel to the Hualiangting reservoir in Taihu County, 45 km, one-hour driving;

• 9:00-10:30: Stop 5: Eclogites and UHP shear zone next to the Hualiangting reservoir (90 minutes walking and observation);

• 10:30-11:30: Drive to the top of the hill and take a group picture;

• 11:30-13:30: Take the bus, go to the Shijiyuan Hotel and have dinner;

• 13:30-18:00: Departure from the Shijiyuan Hotel to the International Conference Center at Nanjing University (362 km, 4 hours driving), have 30 minutes rest in a service area of highway;

• 18:30: Dinner in the International Conference Center.

Contact Information： 

Any inquiry about the Field trip 1, please contact with:

Prof. Wang Qin,  Email: qwang@nju.edu.cn

Mr. Yuan Peng, Email:gscypeng@outlook.com, dic@cags.ac.cn

  DEEP-2024 Field Trip 1 Guidebook-Dabie